Campbell Hausfeld SDM-CAN Network Card User Manual

SDM-CAN
CAN-Bus Interface
User Guide
Issued 26.6.07
Copyright © 2001-2007 Campbell Scientific Ltd.
CSL 419
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workmanship. This guarantee applies for twelve months from date of
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during the guarantee period provided they are returned to us prepaid. The
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•
Equipment which has been modified or altered in any way without the
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•
Batteries
•
Any product which has been subjected to misuse, neglect, acts of God
or damage in transit.
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Campbell Scientific Ltd,
Campbell Park, 80 Hathern Road,
Shepshed, Loughborough, LE12 9GX, UK
Tel: +44 (0) 1509 601141
Fax: +44 (0) 1509 601091
Email: support@campbellsci.co.uk
www.campbellsci.co.uk
Contents
Section 1. Introduction ................................................ 1-1
1.1 General Description .............................................................................. 1-1
1.2 Specifications........................................................................................ 1-2
1.2.1 General Features and Specifications ........................................... 1-2
1.2.2 Electrical Specifications.............................................................. 1-2
1.2.3 Physical Specifications................................................................ 1-3
Section 2. Installation .................................................. 2-1
2.1 Address Switch Configuration.............................................................. 2-1
2.2 Internal Jumper Settings ....................................................................... 2-2
2.3 Connection to the Datalogger and Power Supply ................................. 2-4
2.3.1 LED Status Indication ................................................................. 2-5
2.4 Connection to CAN-Bus....................................................................... 2-6
Section 3. Programming CR10X, CR7 and CR23X
Dataloggers to use the SDM-CAN............ 3-1
3.1
3.2
3.3
3.4
General Principles................................................................................. 3-1
System Limitations ............................................................................... 3-2
The Datalogger Instruction ................................................................... 3-3
Advanced Programming Techniques.................................................. 3-12
3.4.1 Interrupts Using the I/O Connection ......................................... 3-12
3.4.2 Group Trigger ........................................................................... 3-14
3.5 Program Examples .............................................................................. 3-14
3.5.1 Reading CAN Data ................................................................... 3-14
3.5.2 Simple CAN Data Transmission ............................................... 3-15
3.5.3 Building and Sending Data Frames........................................... 3-16
3.5.4 Using the Interrupt Function ..................................................... 3-17
3.5.5 Using the Group Trigger ........................................................... 3-18
Section 4. Programming CR5000 and CR9000
Dataloggers to use the SDM-CAN............ 4-1
4.1 General Principles................................................................................. 4-1
4.2 Datalogger Instruction .......................................................................... 4-1
4.2.1 Reading CAN Data ..................................................................... 4-2
4.2.2 Simple CAN Data Transmission ................................................. 4-3
4.2.3 Digital I/O Triggered CANbus Measurements ........................... 4-4
4.2.4 SlowSequence Instruction........................................................... 4-5
Section 5. Using the RS232 Serial Diagnostic Port... 5-1
5.1 Connecting to the RS232 User Port...................................................... 5-1
5.2 Diagnostic Commands .......................................................................... 5-1
5.3 Loading a New Operating System into the SDM-CAN Interface......... 5-3
Appendix A. Principles of Operation ......................... A-1
A.1 Data Collection ....................................................................................A-1
A.2 Frame Transmission.............................................................................A-1
Appendix B. A Summary of Data Types .................... B-1
Appendix C. Applications of the SDM-CAN on
Networks Complying with the J1939
SAE Standards ...................................... C-1
C.1
C.2
C.3
C.4
J1939 29-Bit Identifier Format ............................................................C-1
J1939 11-Bit Identifier Format ............................................................C-1
J1939 Data Frame Format....................................................................C-2
Retrieving J1939 Accelerator Pedal Position Data using a
CR9000/CR5000 (Bus Speed 250k Baud) ..........................................C-2
C.4.1 Encoding the Identifier Field Values .........................................C-2
C.4.2 Finding the Start Bit ...................................................................C-3
C.5 Retrieving J1939 Accelerator Pedal Position Data using a
CR23X/CR10X (Bus Speed 250k Baud) ............................................C-4
C.5.1 Encoding the Identifier Field Values .........................................C-4
C.5.2 Finding the Start Bit ...................................................................C-5
Appendix D. Examples of CAN Data Frames and Data
Encoding and Decoding ....................... D-1
Figures
1-1
2-1
2-2
2-3
2-4
2-5
SDM-CAN CAN-Bus Interface ........................................................... 1-1
SDM-CAN Internal Jumpers................................................................ 2-3
SDM-CAN Isolation enabled ............................................................... 2-3
SDM-CAN Isolation disabled .............................................................. 2-4
Using the Spring Loaded Terminal Blocks (Top Option) .................... 2-5
Using the Spring Loaded Terminal Blocks (Front Option).................. 2-5
Tables
2-1 Switch Position and Addresses ............................................................ 2-1
2-2 LED Status Indication .......................................................................... 2-6
2-3 CIA CAN Connector Pin Connections................................................. 2-6
3-1 Typical Settings of the CAN Speed Parameters................................... 3-5
5-1 RS232 Pin Out...................................................................................... 5-1
C-1 Mapping of the J1939 Fields into a 29-Bit Identifier ..........................C-1
C-2 Mapping of the J1939 Fields into a 11-Bit Identifier ...........................C-1
C-3 J1939 Data Frame format ....................................................................C-2
C-4 Mapping of J1939 Identifier Field Values into a 29-Bit Identifier......C-3
C-5 Accelerator Pedal Position Value Byte Number..................................C-3
C-6 Mapping of J1939 Identifier Field Values into a 29-Bit Identifier.......C-5
C-7 Accelerator Pedal Position Value Byte Number...................................C-5
Section 1. Introduction
The SDM-CAN interface is designed to allow a Campbell Scientific datalogger to sample data
directly from a CAN-Bus communications network and thereby allow such data to be stored
along with, and in synchronisation with, other data values measured directly by the
datalogger.
To use the SDM-CAN device it is assumed that you have a full working understanding of the
CAN network you wish to monitor. While there are moves to standardise CAN networks for
different types of applications, the SDM-CAN device is designed to be as generic as possible
thus allowing use in a wide range of applications, including research and development, where
you may be working outside the normal standards.
As a result you will need to know details of the electrical configuration of the network, the
speed and CAN standard in use, plus knowledge of the identifiers of the data packets that are
of interest and the way in which data is encoded within those packets at the binary level. This
information may need to be obtained from the designers of the network, from propietary
documentation or from the standards to which a network claims to comply.
Campbell Scientific cannot provide full technical support in the understanding and decoding
of data on all types of CAN networks.
Figure 1-1 SDM-CAN CAN-Bus Interface
1.1 General Description
The SDM-CAN forms an intelligent interface between a Campbell Scientific
datalogger and a CAN-Bus communications network. The SDM-CAN is
configured by the datalogger under the control of the user’s datalogger program.
By this process the SDM-CAN can capture data on the CAN-Bus and filter out
packets of interest to the user. Within each data packet the device is able to read
one or more data values and convert them to numeric values compatible with the
normal data stored by the datalogger.
The SDM-CAN will act as a passive listen-only device with its transmitter
disabled in hardware. Alternatively it can be configured to send/respond to
Remote Frame Requests, allowing it to poll remote devices for data. Data packets
can also be constructed to allow it to send data out onto the CAN-Bus so it then
acts as a sensor itself.
Data is transferred between the SDM-CAN interface and the datalogger using
Campbell Scientific’s high speed SDM communications protocol. This protocol
allows the SDM-CAN to be used in parallel with other SDM devices (including
1-1
SDM-CAN CAN-Bus Interface User Guide
other SDM-CAN interfaces) which might, for instance, be on other CAN-Bus
networks in the same vehicle.
In addition to connectors to the CAN network and the datalogger, an RS232 port
is also provided both for diagnostics and operating system upgrades.
1.2 Specifications
1.2.1 General Features and Specifications
•
Uses Campbell Scientific’s SDM communication protocol to communicate
with the datalogger via a three wire serial multidrop connection. Support is
planned for CR10X, CR23X, CR7, CR5000 and CR9000 dataloggers.
•
Up to 16 units can be used per datalogger, with the modules’ SDM address set
by rotary switch.
•
CAN 2.0A and 2.0B active and passive modes supported
•
Up to 1Mbaud max data rate. Standard baud rates supported are 1M, 800K,
500K, 250K, 125K, 50K, 20K and lower. Other non-standard baud rates may
be possible – please contact Campbell Scientific.
•
Receive and transmit up to 128 different data values from up to 128 CAN
ID’s.
•
Build and send a CAN data frame.
•
Send Remote Frame Requests.
•
Send data frame in response to an external Remote Frame Request.
•
Supports a number of power down modes to allow power saving in power
critical applications.
•
All configuration of the interface is specified within the user’s datalogger
program.
•
LED status flash at power up
•
Additional I/O port for signalling to the datalogger that data is available,
e.g. using an interrupt function.
•
Has a 9 pin, DCE RS232 port with auto baud rate detection (1200 to
115200) for diagnosis and operating software download.
•
Standard operating temperature range (tested), -25ºC to +50ºC. Can be used
over an extended temperature range – contact Campbell Scientific for details.
•
High speed block mode for fast data collection.
•
Buffer assisted burst mode for capturing back to back high speed CAN data.
•
Buffer’s support data frame filtering and triggering.
1.2.2 Electrical Specifications
1-2
•
Power supply range: 7 to 26V DC.
•
Optional (switch selectable) galvanic isolation between the datalogger and the
CAN-Bus. The minimum isolation breakdown is 50V – this barrier is for
signal isolation only, i.e. it is not a safety barrier.
•
Hitachi H8S,16 bit CPU clocked at 10MHz.
•
Uses the latest Philips SJA1000 CAN controller clocked at 16MHz.
•
CAN-Bus physical interface using Philips PCA82C251 driver for 1Mbaud
capability, for use in 12V or 24V systems.
•
CAN-Bus physical connection conforms to CIA draft standard 102 version 2,
9 pin D connector. (The interface will differ from this standard only with
respect to pin 9, which outputs 5V DC instead of 7-13V DC.)
Section 1. Introduction
•
A 3 way, unpluggable screw terminal block for CAN High, Low and G also
provided.
•
Transmit and acknowledge to CAN-Bus can be disabled by a hardware
jumper for safety reasons, e.g. for in-vehicle, listen only monitoring.
•
I/O terminal used for interrupts is pulled low by a 100Kohm resistor and is
driven to 5V via a 1Kohm impedance when an interrupt is pending.
1.2.2.1 Power Consumption
•
Typical active current in self-powered, isolated mode with the CAN-Bus in
the recessive state: 70mA. (this is when the SDM-CAN is not transmitting).
•
Typical active current in self-powered, isolated mode with the CAN-Bus in
the dominant state: 120mA (this is when data is being transmitted from the
SDM-CAN device).
Where the DC-DC converter is not used, and power is provided to the isolated
CAN driver circuits by an external source, the current drain by the SDMCAN is approximately 50 mA lower than the figures quoted above.
•
Typical active current, non-isolated with the CAN-Bus in the recessive state:
30mA.
•
Typical active current, non-isolated with the CAN-Bus in the dominant state:
70mA
•
Typical Standby Current with or without isolation is less than 1mA (in this
mode the CAN hardware is turned off so the module cannot wake on receipt
of CAN data). Current consumption increases to typically 50 mA during
periods of communication to the datalogger or when the RS232 port is active.
1.2.3 Physical Specifications
•
•
•
•
•
Maximum dimensions: width 175mm, height 100mm, depth 23mm (without
mounting brackets).
Weight: 300g without mounting brackets.
The device can be vertically mounted with all the connectors on the top
surface.
The SDM address switch is on the right hand side.
Fittings are available to allow vertical mounting in the CR9000 or on
enclosure chassis plates.
1-3
Section 2. Installation
The SDM-CAN can be mounted in a normal card slot of a CR9000 (using optional special end
brackets), on a chassis plate (using the standard brackets supplied) or can be left freestanding.
CR9000 and CR7 dataloggers require optional SDM connection kits and all dataloggers may
require an upgrade to a version of operating system which supports the SDM-CAN interface.
2.1 Address Switch Configuration
Before installing the SDM-CAN, set the SDM address switch to ensure that the
interface has a unique address on the SDM bus, and that the address is set to
match the commands in the datalogger program relevant to each interface.
The SDM address switch can be set to 1 of 16 addresses. The factory-set address
is 00. Table 1 shows switch position and the corresponding address. The Base 4
address is also shown, as this is the address entered in the datalogger program.
Please see Section 3 before using address F (33 base 4) as this address is often
used as a ‘group trigger’ to synchronise measurements by several SDM devices.
The switch is positioned on the right-hand side of the case, so you may have to
remove the mounting bracket to gain access to this switch.
Table 2-1 Switch Position and Addresses
Switch Setting
Base 4 Address
0
00
1
01
2
02
3
03
4
10
5
11
6
12
7
13
8
20
9
21
A
22
B
23
C
30
D
31
E
32
F
33
2-1
SDM-CAN CAN-Bus Interface User Guide
2.2 Internal Jumper Settings
The SDM-CAN interface is fitted with a number of jumpers which configure the
connection to the CAN network.
Prior to setting these jumpers you need to give some consideration on how best to
connect the SDM-CAN interface to the network:
1) Decide whether the CAN network is already terminated, or if the SDM-CAN
needs to provide termination. In most instances the network will already be
terminated and so the default setting is no termination.
2) Decide whether to operate the SDM-CAN in a mode where it is isolated from
the CAN network. This is the ‘safest’ mode of operation as it minimises the
risk of corrupting the CAN data by the formation of grounds loops which
could inject noise onto the CAN-Bus. The default setting is to run in isolated
mode.
3) If running in isolated mode decide whether the SDM-CAN will supply power
via a built-in DC-DC converter for the isolated CAN interface components, or
whether power will be sourced from an external supply. Using a converter
adds 40-50mA to the power consumption of the SDM-CAN when it is active.
However, if a converter is not used, power must be provided from elsewhere
(see below). The default setting is for the converter to be OFF, although for
many applications you may need to turn it on once you have considered the
implications for your power supply.
4) Decide whether the transmit functions of the SDM-CAN interface need to be
enabled in hardware. The disabled mode of operation is the safest, especially
in vehicle applications, as it avoids the risk of the SDM-CAN sending bad
data onto the CAN network. However, in some modes of operation,
transmission is obligatory e.g. to let the SDM-CAN request data, acknowledge
data or to transmit data onto the bus. If transmission is to be enabled, the
relevant jumpers need to be changed. Additionally transmission must be
enabled by sending the SDM-CAN an instruction which both enables and
specifies the method of transmission. See Section 3.3, data type 32, below.
Access to the jumpers requires the removal of the lid of the SDM-CAN. Please
follow anti-static precautions during the removal of the lid and also when
changing the jumpers. Refer to Figure 2-1 for details of the jumper positions.
Labels are also provided in white writing on the circuit board.
If white jumper block not fitted then refer to Figure 2-2 for isolation enabled and
Figure 2-3 for isolation disabled.
2-2
Section 2. Installation
Transmission of
CAN data is
hardware disabled
by default. To
enable transmission,
move the jumper to
the TX enable
position.
SDM-CAN PCB
Once the case lid
has been removed.
OBSERVE ANTISTATIC
PRECAUTIONS.
This jumper block
is used to select
isolated or nonisolated CAN-Bus
interface. The
jumper block can
be removed and
rotated so that the
red bar is nearest
to the mode arrow
head. The default
is for isolation
enabled.
The CAN-Bus
termination
impedance is
disabled by default.
If you need the bus
to be terminated,
then move the
jumper to the 120R
IN position.
The DC-DC converter is off by
default. This will reduce power
consumption from the +12V
supply but means that the isolated
circuits must be powered
externally. To enable the DC-DC
converter move the jumper to the
DC-DC ON position.
Figure 2-1 SDM-CAN Internal Jumpers
Figure 2-2 SDM-CAN Isolation enabled (default)
2-3
SDM-CAN CAN-Bus Interface User Guide
Figure 2-3 SDM-CAN Isolation disabled
2.3 Connection to the Datalogger and Power Supply
To allow communication between the SDM-CAN and a datalogger, firstly connect
it to the datalogger’s SDM port, and then connect to a 12V power supply. Both the
datalogger and the SDM-CAN 12V power supply must share a common ground.
The SDM port is provided in different ways on different dataloggers:
CR10X and CR23X – use the C1, C2 and C3 control ports.
CR7 – a special SDM terminal block is provided as part of the SDM upgrade kit.
This terminal block is fitted on a small module adjacent to the 9 way ‘Serial I/O’
connector on the front of the 700 control module. The connections are labelled C1,
C2 and C3.
CR5000 – use the port connections labelled SDM-C1, SDM-C2 and SDM-C3.
CR9000 – connections are made via the 9 way, ‘CSI Serial I/O’ connector on the
9080 PAM card. Pins 6, 7 and 8 are used as C3, C2 and C1 respectively. Pin 2 is
ground. Campbell Scientific offers connection modules for this port which allow
access to the SDM function as well as retaining normal function of the serial port,
please contact your local sales office for further details.
The SDM-CAN requires a nominal 12V power supply connection (7-26V) rated
at 150mA. Normally the datalogger supply can be used for this feed. A connection
to ground is also required. If the 12V supply is separate from the datalogger, both
the ground of the supply and datalogger must be connected together.
The SDM and power connections are made to a black terminal block on the lefthand side of the SDM-CAN interface. This terminal block has special spring
loaded terminals which are simple to use and highly resistant to loosening in high
vibration environments. To open the terminal simply insert the tip of a small flat
blade screw driver (3mm width) into the rectangular hole above the circular
terminal hole. Push in the blade of the screwdriver until the spring is released and
the terminal opens. Insert the pre-stripped wire and then remove the screwdriver.
See Figure 2-4. If space is limited, as when the unit is mounted in an enclosure
etc., the screwdriver can be inserted into the front of the terminal block to push
open the spring, as shown in Figure 2-5.
2-4
Section 2. Installation
Figure 2-4 Using the Spring Loaded Terminal Blocks (Top Option)
Figure 2-5 Using the Spring Loaded Terminal Blocks (Front Option)
Where you need to install more than one wire in a single terminal connector, use
only stranded wires and twist the wires together before inserting them in the
terminal. This type of terminal is not suitable for use with multiple solid core
wires unless the wires are joined externally, e.g. using a ferrule.
Route the wires from the SDM-CAN interface to the datalogger connections using
the shortest route. Avoid running them near cables which could cause noise
pickup. In noisy environments use low capacitance signal cable with an overall
foil screen, connecting the screen to the datalogger power ground.
Where multiple SDM devices are in use connect them in parallel to datalogger
SDM ports, making sure each device has a unique SDM address. Ensure that the
maximum cable length between the datalogger and the SDM-CAN does not
exceed 3 metres.
An additional I/O terminal is provided on the SDM-CAN for use with dataloggers
which support interrupt driven logging events. This might typically be used to
enable the rapid capture of time critical CAN data, where the I/O port can be used
to indicate to the datalogger that data has been captured and is available for
immediate collection (see below). In most applications this function will not be
used and the terminal need not be connected. Where it is required, it should be
connected to a digital input on the datalogger.
2.3.1 LED Status Indication
When power is applied to the SDM-CAN the red ‘STATUS’ LED will flash to
indicate the current status of the unit as a result of the power-up checks.
2-5
SDM-CAN CAN-Bus Interface User Guide
If the LED flashes once, the module has passed all power-up tests and should
operate correctly. The other flash sequences are shown below. Problems with the
operating system can normally be fixed by reloading the operating system.
Please contact Campbell Scientific if you are unable to resolve the problem.
Table 2-2 LED Status Indication
Number of
flashes
Indication
1
SDM-CAN is ok.
2
OS signature bad.
10
OS downloaded has failed.
2.4 Connection to CAN-Bus.
The physical connection to the CAN-Bus is achieved by one of two methods
which is by either the 3 way un-pluggable screw terminals or the 9 pin ‘D’ plug
which conforms to CIA draft standard 102 version 2.
The basic connections of the CAN-Bus to the three-way terminal are CAN High,
CAN Low and 0V ground reference. The 3 way screw terminal is marked as
‘G H L’ on the SDM-CAN case, where G=Ground, H=CAN High, L=CAN Low.
The CIA, 9 pin, ‘D’ connector pin configuration is shown in Table 2-3.
Table 2-3 CIA CAN Connector Pin Connections
Pin
Function
1
Reserved, NOT INTERNALLY CONNECTED.
2
CAN Low.
3
CAN Ground.
4
Reserved, NOT INTERNALLY CONNECTED.
5
CAN Shield.
6
CAN Ground.
7
CAN High.
8
Reserved, NOT INTERNALLY CONNECTED.
9
CAN +5volts. Input or output (see text).
If the SDM-CAN hardware is configured (in either isolated or non-isolated mode)
with the DC-DC converter ON, then Pin 9 of the 9 pin ‘D’ connector will provide
+5V +/-10% at up to 40mA to any external device. If isolation is enabled and the
DC-DC converter is set to OFF then this pin acts as an input for an external power
supply capable of providing +5volts +/-10% at up to 100mA to provide power to
the isolated circuitry of the SDM-CAN.
NOTE
2-6
The 3-way terminal block and CIA connector are connected in
parallel internally and are not two separate connections to different
CAN interfaces.
Section 2. Installation
Please refer to the documentation for your CAN network to check the preferred
method of connection. For many applications various standards will apply giving
recommended practises for connection. Apart from the choice of connector some
standards recommend different ways of ‘tapping’ into CAN networks and also
recommend maximum lengths for ‘T’s or ‘stubs’ off the network. For instance, at
the highest baud rate of 1Mbit/s, ISO11898 recommends a maximum bus length
of 40 m and a maximum stub length of 0.3 m. These lengths increase significantly
at lower bit rates.
As discussed above you also need to consider:
•
If the SDM-CAN should terminate the network
•
If it should be configured in isolated mode
•
If transmission should be enabled
•
The source of power for the isolation hardware.
2-7
Section 3. Programming CR10X, CR7
and CR23X Dataloggers to use the
SDM-CAN
This section describes the programming methods used for the above dataloggers to configure
and use the SDM-CAN Interface. This section also covers general principles and techniques
which are relevant to the other dataloggers,
3.1 General Principles
The SDM-CAN interface is controlled by instructions that the user enters in the
datalogger program. For the dataloggers covered by this section the Program
Instruction is number P118. Full details of the instruction are given below. This
sub-section has been written to introduce the parameters of Instruction P118 and
how they allow you to control the different operations of the SDM-CAN.
The initial function is to configure the SDM-CAN interface when the datalogger
program is compiled. At this stage, the datalogger analyses the P118 parameters
used by the program and sends the relevant commands to the SDM-CAN to
configure it to perform appropriate tasks.
The most common configuration task, at compile time, is to set up the SDM-CAN
to instruct it to filter out only the data frames of interest from all data ‘passing on
the bus’.
The other configuration task done at this point is to specify the speed at which the
CAN-Bus is to operate. It is important to ensure the parameters which define the
speed are set correctly and all instructions have the same values entered for these
parameters otherwise either no data will be received, or you risk corrupting data
on the bus, if the SDM-CAN is enabled for transmission.
The next common function is to read data back from the SDM-CAN, to decode it,
and to store it in input locations once the program is running. A single entry of
P118 in the program can both configure the SDM-CAN during program
compilation and also cause data to be read back from the SDM-CAN when that
instruction is executed during normal program execution.
Similarly there is also a function which is used to send simple data from the
datalogger input locations onto the CAN-Bus via the SDM-CAN. Again a single
call of P118 can both configure and then transmit the data when the program is
running.
A more complicated version of this function is also possible where multiple P118
instructions are used to build a transmit data frame within the SDM-CAN, made
up of a series of fixed or variable data values from input locations. A subsequent
P118 is used to instruct the SDM-CAN to transmit the frame either immediately or
in a response to a remote frame request from another device.
Finally there are some special functions normally achieved by a single a call of
P118. One such function is used to change internal ‘switches’ within the SDMCAN which control its mode of operation, e.g. power mode, response to failed
transmissions etc. Similar functions also allow you to read back the settings of
these ‘switches’ into input locations and also to read and/or reset the number of
CAN errors detected and to also determine the general status of the SDM-CAN
interface.
3-1
SDM-CAN CAN-Bus Interface User Guide
3.2 System Limitations
The SDM-CAN interface, in combination with a datalogger, has some limitations
of which you need to be aware:
1) Memory Allocation and P118
Firstly, as discussed above, when the datalogger compiles a program with
P118 in it, it sends commands to the SDM-CAN instructing it what to do at
run time. When it does this the SDM-CAN allocates some of its memory (a
‘bin’) for each call of P118 in the program. Appendix A discusses the
operation of these bins and other buffers in the SDM-CAN in more detail.
However, most users only need to know that there is a limit of 128 bins in the
SDM-CAN thus constraining the number of instances of P118 for any one
SDM-CAN to 128.
It is, of course, possible to have several SDM-CAN devices connected to the
datalogger(s), each with separate SDM addresses, and each with up to 128
calls of P118.
2) Data Capture Limitations
Another limitation is the capability of the overall speed at which the
datalogger can pick up and transfer data values back to its memory. These
limitations do not arise within the SDM-CAN interface itself, as it uses a high
speed CAN interface along with a fast microprocessor. Data can therefore be
captured off the CAN-Bus at close to the maximum bus loading at the
maximum baud rate. However, the limitations arise from the datalogger itself,
both in terms of its capability to call P118 often enough (especially when
making other measurements) and also in its capability to transfer the data from
the SDM-CAN back into its memory over the SDM communications port.
The exact throughput possible is determined by a very complicated
combination of variables, including the speed of the datalogger in question,
the program it is running, how many SDM devices are in use and, to a lesser
degree, other tasks it is running, e.g. communications activity.
In practise, for fast data, it will not be practical to capture every single data
packet. However, the SDM-CAN will be used to sample the last reading it
received on the CAN-Bus before the datalogger requests data.
If a new data value has not been captured from the CAN-Bus since the last
value was transferred to the datalogger, the SDM-CAN can either be set to
always return the previous value captured (default) or it can be configured
(see the internal software switch settings below) to return the standard out of
range value to the datalogger, i.e. –99999 if the value has already been read.
This value will also be returned in the event of other errors including
communication errors between the datalogger and SDM-CAN.
Data stored in packets on the CAN-Bus can be encoded in a number of
different ways. The SDM-CAN itself can cater for many different types of
data, but there are some limitations imposed by the way in which the data is
stored in the datalogger. The prime limitation is that data read into the
datalogger is first converted into a 4 byte floating point format which can only
resolve, at most, 23 bits, or roughly 7 digits, of the decimal equivalent of any
number stored. Furthermore, when data is stored to final storage, the
resolution is truncated again to either 4 or 5 digits (with the exception of the
CR5000/9000 dataloggers which also support storage in IEEE4 format).
To avoid over-running the datalogger’s internal floating point resolution, the
maximum length of integer that the SDM-CAN can send or receive is
therefore limited to 16 bits. This limited resolution can cause problems when
reading CAN data where data is encoded as 32 or 64 bit integers.
3-2
Section 3. Programming CR10X, CR7 and CR23X
The simplest solution, in those cases, is to read the value as a series of 16 bit
integers written to separate input locations in the datalogger. These can then
either be combined once the data has been recovered to a computer or, if
some of the resolution is not needed, the data values can be combined in the
datalogger using its normal maths functions. You must bear in mind,
however, the limitations of the 4-byte floating point calculations and the
output resolution of the datalogger.
The CAN standard also allows some types of data to be spread across several
data packets, where those data packets all have the same identifier. Such data
normally would consist of fixed identifiers stored as ASCII data, which do not
normally have to be logged. Reliably capturing such data with the SDM-CAN
is not possible, with the current software, unless the sequential packets are
transmitted relatively slowly. Please contact Campbell Scientific for further
information if you have a requirement to do this.
3)
When transmitting CAN frames from the SDM-CAN there are situations
where some frames are not transmitted. This is because the SDM-CAN has a
two layer buffer for transmitted frames. This allows a frame to be transmitted
whilst a new frame is being built. However if your program tries to send
frames too quickly, before earlier frames are sent, the frames will be
overwritten and lost.
This scenario generally does not happen with CR10X / CR23X loggers as
they are not fast enough. But with the CR5000 / CR9000 loggers it is possible
to overrun the double buffer especially in pipe line mode if you are
transmitting more than 2 frames per scan. It is recommended to use sequential
mode in this case as it allows a delay between CAN-BUS instructions.
3.3 The Datalogger Instruction
The instruction used by all of the dataloggers covered in this chapter is Instruction
118. The structure of the instruction and parameter types is shown below. This
structure is given in the same format that normal instructions are shown in the
datalogger manuals. Please refer to the datalogger manual for a description of the
data types, entry of the instruction and how to index (‘--’) parameters.
NOTE
In some previous versions of datalogger operating systems, Instruction
118 was used for the now obsolete OBDII interface. Older datalogger
manuals and Edlog help systems may still refer to this instruction.
Please make sure you are using a version of the operating system that
supports P118 and refer to a more recent datalogger manual or Edlog
help system.
It will be apparent for some functions of P118 that some parameters are not
relevant or have no function. In these cases simply leave the parameter(s) at their
default value(s) which is normally zero.
3-3
SDM-CAN CAN-Bus Interface User Guide
Instruction 118: SDM-CAN
PARAM. NUMBER
DATA TYPE
DESCRIPTION
RANGE
01:
2
SDM address
00..33
02:
2
TQUANTA
0-63
03:
2
TSEG1
0-15
04:
2
TSEG2
0-7
05:
4
ID bits 0-10
0-2047 ‘--’ Set 11bit ID.
06:
4
ID bits 11-23
0-8191
07:
2
ID bits 24-28
0-31
08:
2
Data type
0-33
09:
2
Start bit number
0-64, ‘--’ Left-hand referenced LSB.
10:
2
Number of bits
0-64, ‘--' Enable Interrupt mode.
11:
4
Number of values
0-99
12:
4
Input Location
13:
FP
Multiplier
14
FP
Offset
SDM Address (Parameter 01:)
This parameter should match the SDM address set by the address switch on the
side of the module to which this instruction applies. Please see section 2.1, above,
for more details. Also see the section below, regarding the special function of
address 33.
TQUANTA, TSEG1, TSEG2 (Parameters 02:, 03:, 04:)
These parameters are used to set the bit rate and other timing parameters for the
CAN-Bus network. On some networks the relationship between some of these
parameters is predefined and just one parameter, the baud rate, is quoted. For
maximum flexibility, though, the user is given access to all of the relevant
parameters. Table 3 gives some typical values of the parameters for a range of
baud rates. However, be sure to check that these are correct for your specific
network before using them.
The parameters are entered as integer numbers which define various times that
control when the binary data is sampled by the CAN hardware. The following
discussion and nomenclature is common to the set-up of most CAN controller
chips. If you are not familiar with CAN at this level please seek the advice of
someone who is familiar with your network to determine these parameters.
The overall speed of the network is specified by the baud rate, in bits per seconds,
which define the time per bit (tbit) by the simple relationship:
tbit = 1 / baudrate
Within the time period for each bit the CAN standards define three different time
segments which ultimately control when the CAN hardware samples the signal.
3-4
Section 3. Programming CR10X, CR7 and CR23X
This is often shown in a diagram, thus:
Bit time (tbit)
S-SG
PROP_SEG
PHASE_SEG1
PHASE_SEG2
tTSEG1
1 time-quanta (tq)
tTSEG2
Sample point
The bit time is divided into time-quanta (tq), of which there are between 8-23
time- quantum in the bit time. The tq (in seconds) used by the SDM-CAN is set
by the scaling factor TQUANTA (parameter 02). This is the parameter that largely
determines the baud rate. To work out a suitable value of TQUANTA, knowing
the required tq, the following equation is used:
TQUANTA = tq * 8*106
The first time segment is known as the synchronisation segment (S-SG) and by
convention is one time-quanta long.
This is followed by two segments known as the propagation segment and phase
segment one. These are determined by the characteristics of the network and other
devices on the network. The total of these two time segments determines the time
when the SDM-CAN samples the data bit and is known as tTSEG1. The final
segment is known as phase segment two or tTSEG2
The relationship between these times is summarised by:
tbit=tq+tTSEG1+tTSEG2
t TSEG1 (in seconds) is set using the scaling factor TSEG1 (parameter 03), the value
of which is calculated using the following equation:
TSEG1 = tTSEG1 / tq
tTSEG2 is set using scaling factor TSEG2 (parameter 04) the value of which is
calculated using:
TSEG2 = tTSEG2 / tq
When determining the settings of these parameters it is important to ensure that
the size and total number of tq exactly matches the baud rate at which the network
is to run, as the tolerance allowable is normally quoted as +/-1.5%.
The relative settings of TSEG1 and TSEG2 are not so critical as they control when
the hardware samples the data value and there is normally quite a wide tolerance
over which this will work.
If no data other than the baud rate of a network is available a simple ‘rule of
thumb’ is to set the parameters such that there are at least eight time-quanta in the
span of the bit width and that the sample point is 80% through the bit width.
3-5
SDM-CAN CAN-Bus Interface User Guide
Table 3-1 Typical settings of the CAN Speed Parameters
Baud rate
NOTE
TQUANTA
TSEG1
TSEG2
1M
1
5
2
800 K
1
7
2
500 K
2
5
2
250 K
4
5
2
125 K
8
5
2
50 K
16
7
2
20 K
40
7
2
The same three values for these parameters should be used in every
call of the P118 instruction in the datalogger program.
ID (Parameters 05:, 06:, 07:)
A CAN data frame includes an identifier (ID) which is used by devices on the
network to identify each type of packet on the network. Some standards reserve
certain IDs or ranges of IDs for specific functions. The J1939 SAE standard for
instance reserves certain parts of the ID to identify the type of data, its priority and
its origin (see Appendix C for a discussion of this standard and use with the
SDM-CAN). The SDM-CAN is, however, transparent to any special meaning of
the ID; each packet is only referenced by the full ID. The CAN 2.0A standard uses
an ID with 11 bits, while CAN 2.0B uses 29 bits.
When entering IDs into Instruction P118, three parameters are used. This is
because the ID size, in number of bits, is too large to be encoded into a single
parameter.
The first ID parameter (parameter 05) sets bits 0..10, entered as a number between
0 and 2047. This parameter also determines whether an 11-bit or a 29-bit Identifier
is set. If you index this parameter then an 11bit Identifier is set; the following two
parameters are then irrelevant and are normally left at zero.
The second ID parameter (parameter 06) encodes bits 11..23 entered as 0 to 8191.
The third ID parameter (parameter 07) is for bits 24 to 28 entered as 0 to 31.
NOTE
CAN networks either work with 11 or 29 bit IDs. As a general rule
you cannot have packets with different length IDs on the same
network. Therefore make sure parameter 05 specifies the same
length ID for all calls of P118.
Data Type (Parameter 08:)
This parameter determines the type of data involved and/or the type of function
this call of P118 will perform. The data type parameter is entered as a two-digit
parameter in the range of 0-33. A summary table of the data types described below
is given in Appendix B of this manual for quick reference.
As a general rule, this function is applied only to data packets with the ID
specified in parameters 05..07. The action applies to a certain number of bits
within the data frame that is specified in parameter 10, starting at the bit specified
in parameter 09. In some cases the number-of-bits parameter is overridden
3-6
Section 3. Programming CR10X, CR7 and CR23X
implicitly by the data type specified, e.g. IEEE4 data is always 32 bits in length.
For integer values, the longest integer you read or send from one datalogger input
location is 16 bits as a result of limitations in the datalogger. See section 3.2 above
for an explanation and work-arounds.
For data types that read or set status, switches or error codes, only the input
location parameter, multiplier and offset are used. Other parameters can be set to
zero.
As defined by the CAN standard, data is always encoded or decoded on the
assumption that the least significant bit is transmitted last or is on the ‘right-hand
side’ of a data frame. The data frame can be from 0 to 64 bits in length, but is
normally a multiple of 8-bit bytes. This means there are typically 0-8 bytes in the
data frame.
Please refer to Appendix D for examples of typical data frames and how to decode
data within them. Appendix D also contains diagrams to show the method of
pointing to the start bit within the data frame.
For convenience the start bit can be referenced from either end of the frame (see
parameter 09 below), but this does not change the direction in which data is
encoded or decoded. Within a byte the MSBit is always first (on the left).
Where the number-of-values parameter (parameter 11) is greater than one, the
same function is applied to successive sections of the data frame, moving towards
the ‘left’ of the frame. Data values are read to, or written from, successive input
locations in the datalogger.
The data types can be grouped into different type of functions, as follows:
Collect and retrieve a data value:
This function programs the SDM-CAN to capture a particular data packet and pass
specific data from the data frame within that packet back to the datalogger.
Parameter
Value
Data Type
1
Unsigned integer, most significant byte 1st.
2
Unsigned integer, least significant byte 1st.
3
Signed integer, most significant byte 1st.
4
Signed integer, least significant byte 1st.
5
4 byte IEEE floating point number, most significant byte 1st.
6
4 byte IEEE floating point number, least significant byte 1st.
Build a data frame for transmission:
The data will be sent to the SDM-CAN where it is written into a working 8-byte
buffer in memory. The data is written starting at the bit position determined by
parameter 09 and the number of bits stored by parameter 10. When the data type
parameter is set in the range of 7..12, the data is written to the buffer directly,
i.e. it overwrites any previous data in that memory (see also types 13..18).
3-7
SDM-CAN CAN-Bus Interface User Guide
Once the buffer is complete, after using other P118s with this range of data types
to construct the desired data frame, it is sent out onto the CAN-Bus by a further
call of P118 with parameter 08 set to 25 or 26 (see below).
Parameter Data Type
Value
7
Unsigned integer, most significant byte 1st.
8
Unsigned integer, least significant byte 1st.
9
Signed integer, most significant byte 1st.
10
Signed integer, least significant byte 1st.
11
4 byte IEEE floating point number, most significant byte 1st.
12
4 byte IEEE floating point number, least significant byte 1st.
Setting parameter 08 in the range of 13..18 has the same function as in the7..12
range, except that the data values written are logically ‘OR’ed with values
previously written into the memory buffer. This allows complex bit patterns to be
defined, sometimes changing only as little as one bit at a time.
Parameter Data type
Value
13
Unsigned integer, most significant byte 1st.
14
Unsigned integer, least significant byte 1st.
15
Signed integer, most significant byte 1st.
16
Signed integer, least significant byte 1st.
17
4 byte IEEE floating point number, most significant byte 1st.
18
4 byte IEEE floating point number, least significant byte 1st.
Transmit individual data values onto the CAN-Bus:
This range of parameter values instructs the datalogger to send a data value to the
SDM-CAN in the format specified; it is loaded into the specified point in a data
frame and then immediately transmitted onto the CAN-Bus. Bits within the data
frame that are not set are left at zero. The data frame length is set to the minimum
size (in whole bytes) required to hold the type of data value specified.
Parameter Value
3-8
Data Type
19
Unsigned integer, most significant byte 1st.
20
Unsigned integer, least significant byte 1st.
21
Signed integer, most significant byte 1st.
22
Signed integer, least significant byte 1st.
23
4 byte IEEE floating point number, most significant
byte 1st.
24
4 byte IEEE floating point number, least significant
byte 1st.
Section 3. Programming CR10X, CR7 and CR23X
Transmit a previously built data frame on to the CAN-Bus (type 25):
When parameter 08 is set to 25, P118 will cause the datalogger to tell the SDMCAN to transmit a previously ‘built’ data frame which is stored in the memory
buffer for this packet ID (see data types 7..18 above).
The length of the data frame transmitted is determined by parameter 10. If
number of bits is less than a complete number of full bytes (1-8) then the number
of bytes sent will be rounded up and all unused bits will be set to zero.
The data start bit position will normally be set to one so the data frame starts at the
beginning of the memory buffer. However, you can enter a value greater than one
to allow part of the buffer to be transmitted, which can simplify some binary
masking operations.
The memory buffer is left unchanged after transmission.
Set-up previously built data frame as a Remote Frame Response (type 26):
When parameter 08 is set to 26, P118 will configure the SDM-CAN to use a
previously ‘built’ data frame as remote frame response for packets of the specified
ID. The length and start positions are specified as for data type 25.
Read error counters (type 27):
This will return 4 values, in successive input locations starting at the location set
by parameter 12, which show certain errors the SDM-CAN has recorded. The
errors are written in the following order: transmit, receive, overrun and watchdog
counts. Each is a count from 0 to 255.
The transmit, receive and overrun counters are measures of the errors on the CANBus network as defined by the CAN standards. If the transmit counter reaches 255
then the CAN device goes into a ‘bus-off’ state, where it effectively disconnects
itself from the network.
If the SDM-CAN switches to the ‘bus-off’ state, any further reads of the error
counters will show the transmit counter fixed at 127. The counters then need to be
reset to enable further use of the SDM-CAN (see data type 28, below). If this
situation occurs on a regular basis, firstly check the datalogger program (P118
parameters). If these are correct, check the structure and design of the network.
The watchdog counter only increments (and is automatically reset) when the
SDM-CAN ‘crashes’ either due to an internal software error or a hardware fault.
Please contact Campbell Scientific for further advice.
Read and reset the error counters (type 28):
This functions in exactly the same way as type 27 except that after reading the
error counters they are reset to zero. This will also re-enable the SDM-CAN
interface to the CAN-Bus if it has automatically entered the ‘bus-off’ state.
When the counters are reset, the CAN controller chip enters a special state and
waits until it sees a period equal to 11 successive bits of inactivity on the CANBus before it returns to the normal ‘on-line’ state. Therefore this function should
not be called too frequently otherwise data may be lost.
3-9
SDM-CAN CAN-Bus Interface User Guide
Read status (type 29):
This data type instructs the datalogger to request the current status of the
SDM-CAN and writes the results into a single, specified, input location. The
status is encoded within that location in the format ‘abcd’ where each letter is a
digit in the range 0 to 9 indicating a different type of status information.
Status ‘a’:
0
This digit is currently unused.
Status ‘b’:
0
This digit is currently unused.
Status ‘c’:
0
This digit is currently unused.
Status ‘d’:
0
Bus-On; the SDM-CAN is involved in bus activities. All of
the error counters are less than 96.
1
Bus-On; the SDM-CAN is involved in bus activities. One
of the error counters is equal to or greater than 96.
2
Bus-Off; the SDM-CAN is not involved in bus activities.
All of the error counters are less than 96.
3
Bus-Off; the SDM-CAN is not involved in bus activities. One of
the error counters is equal to or greater than 96.
See data type 28 above for details of the error counters and how to reset them.
Read the signature and version number of the SDM-CAN operating system (type 30):
This will return the OS signature and the OS Version number in separate
locations. If the SDM-CAN detects that the OS signature is bad then zero will be
returned.
Send Remote Frame Request (type 31):
A special type of CAN frame, called ‘remote frame request’ is transmitted with
the CAN ID specified.
Set SDM-CAN internal software switches (type 32):
This data type instructs the datalogger to change some internal software switch
settings that control the way it works. The new switch settings are read from a
specified input location. The settings are encoded within that location in the
format of a four digit number. For explanation purposes the four digits are
represented as ‘abcd’ where each letter is a digit in the range 0 to 9 which
indicates a different type of switch setting.
3-10
Section 3. Programming CR10X, CR7 and CR23X
Once set the switches remain set until changed by another call of P118 or on
loading a different program. Therefore it is only necessary to call a P118 to set
these switches once, after program compilation, or when a switch needs to be
changed using a call of P118 within an IF..THEN program construct (see the
program examples below).
Switch ‘a’:
0
This digit is currently unused; enter zero
Switch ‘b’:
0
SDM-CAN returns the last value captured from the network,
even if read before (Default)
1
SDM-CAN returns –99999 if a data value is requested by the
datalogger and a new value has not been captured from the
network, since the last request.
2-9
Currently unused
0
Disable I/O Interrupts (Default) – see section 3.4.1
Switch ‘c’:
Switch ‘d’:
1
Enable I/O Interrupts, pulsed mode
2
Enable I/O Interrupts, fast mode
3-7
Currently unused
8
Set low power standby mode. The SDM-CAN cannot wake from
this state as a result of CAN-Bus activity. Setting this switch to
any other value will bring the SDM-CAN out of standby.
9
Leave this switch setting unchanged
0
Listen only mode, no CAN transmission or acknowledgement to
a correctly received CAN frame is possible. The SDM-CAN runs
in ‘Error Passive’ mode (Default).
1
One shot transmission, no re-transmission will occur in the
event of loss of arbitration or error. Frames received correctly
from an external node are acknowledged
2
Self-reception. A frame transmitted from the SDM-CAN that was
acknowledged by an external node will also be received by the
SDM-CAN but no re-transmission will occur in the event of loss
of arbitration or error. Frames received correctly from an
external node are acknowledged
3
Normal, re-transmission will occur in the event of loss of
arbitration or error. Frames received correctly from an external
node are acknowledged. This is the usual setting to use if the
SDM-CAN is to be used to transmit data.
4
One shot transmission and self test mode. The SDM-CAN will
perform a successful transmission even if there is no
acknowledgement from an external CAN node. Frames received
correctly from an external node are acknowledged
5
Self-reception and self test mode. The SDM-CAN will perform a
successful transmission even if there is no acknowledgement
from an external CAN node. Frames received correctly from an
external node are acknowledged. The SDM-CAN will receive its
own transmission
6
Normal and self test mode. The SDM-CAN will perform a
successful transmission even if there is no acknowledgement
from an external CAN node. Frames received correctly from an
external node are acknowledged.
7
Similar to switch setting 'd-3' , but this setting is 'remembered' at
power-up. During power-up, the SDM-CAN will acknowledge all
valid messages.
NOTE: This setting relies on the datalogger having set up the
SDM-CAN before use.
8
Not defined
9
Leave this switch setting unchanged
3-11
SDM-CAN CAN-Bus Interface User Guide
NOTE
Please refer to the CAN standards and your own network
documentation for a more detailed explanation of the switch ‘d’
modes. It is important to choose the correct setting when the
SDM-CAN is required to transmit data. Also remember to check the
jumper settings inside the SDM-CAN if enabling transmission, as
the default setting is for transmission to be disabled in hardware.
Read SDM-CAN internal switches (type 33):
This data type returns the internal switch settings, into a specified input location.
The switch values shown are encoded in the same way as they are set (see type 34
above), with the exception that a switch setting of 9 is reserved to show an
undefined error (please contact Campbell Scientific if such an error occurs).
Start Bit Number (Parameter 09:)
The start bit number is used to point to the least significant bit (LSB) of the data
value within the CAN data frame to which this instruction relates. Within CAN
data frames there is no general standard as to the order or format of the binary
data. ISO11898 does specify that data should be sent with the most significant bit
(MSB) first, least significant bit (LSB) last. Most diagrams show the MSB on the
left and the LSB on the right. However, some users may find the start point for the
data is referenced in the opposite fashion, i.e. as a count from the left side of the
frame, and so the SDM-CAN supports both methods of referencing the start point.
By default the SDM-CAN follows the ISO standard and the LSB is referenced to
the right-most bit of the frame. The bit number can range from 1 to 64 as there are
up to 64 bits in a CAN frame. If the parameter is indexed, (marked ‘--’) then the
reference is changed to point to the LSB relative to the left-hand most bit of the
frame. Please note, though, that choosing this option does not have any automatic
affect on the type (direction) of encoding or decoding used – it only changes the
method of pointing to the LSB.
NOTE
When entering the start bit, you should always point to the position
of the least significant bit of the data to be decoded/encoded. Please
refer to Appendix D for diagrams and examples of typical data
types.
Number of Bits (Parameter 10:)
This relates to the number of bits to use in this transaction. This number can range
from 1 to 64 as there are up to 64 bits in a CAN frame. If this parameter is indexed
(‘--’) then, when a new value is received, the SDM-CAN, relevant to this
particular call of Instruction P118, will pulse the I/O port to indicate to the
datalogger that the data has been captured and can be read (see below).
NOTE
3-12
For some data types this parameter will be overridden by a fixed
number of bits required by the data type; even so the interrupt
setting can still be set. For integer values, the longest integer you
can read or send from one datalogger input location is 16 bits as a
result of limitations within the datalogger (see section 3.2 above for
an explanation and work-arounds.
Section 3. Programming CR10X, CR7 and CR23X
Number of Values (Parameter 11:)
This is the number of values that will be transferred to or from the datalogger in
one operation. For each value transferred, the number of bits (parameter 10) will
be added to the start bit number (parameter 9) when the start point is referenced to
the right-hand side of the data frame. If referenced to the left-hand side, then the
number of bits is subtracted from the current bit position. The consequence of this
is that successive values are always from right to left in the frame.
Location (Parameter 12:)
This is the start input location where data will be read from or stored to. For any
remaining values/repetition, each value will be read from, or stored into, the next
incremental location.
Multiplier (Parameter 13:)
The data written to, or read from, an input location is multiplied by this parameter.
Offset (Parameter 14:)
The data written to, or read from, an input location has this offset parameter added
to it.
3.4 Advanced Programming Techniques
3.4.1 Interrupts Using the I/O Connection
The I/O port can be used to signal to a datalogger that specific data has been
captured, by the SDM-CAN, from the CAN network and is available for collection
by the datalogger.
The main application for this is where CAN data needs to be captured at a much
faster rate than the normal scan interval of the datalogger and the requirement is to
capture as many CAN packets as possible. In this case the interrupt facility can be
used to give capture of the CAN data as a higher priority over the normal
scheduled measurement tasks, allowing the data to be captured at the highest rate
possible.
The interrupt facility can also help solve the conceptual problem of capturing data
into the datalogger from another system (one of the other devices on the
CAN-Bus) which is running on a different asynchronous clock from the
datalogger itself. This problem needs some consideration in all applications except
those where the datalogger can be made the master (i.e. where it requests data
from the remote devices when its needs the data).
In other applications one has to cater for the possibility that data might not be
available from the CAN network when the datalogger clock causes the datalogger
to run its program. This can happen even when the CAN data is being transmitted
at the same rate as the datalogger is running, simply because the two system
clocks drift relative to each other. The interrupt facility allows you to ensure that
data can be captured at the highest possible rate, but you still have to use special
programming and/or data analysis techniques to synchronise the data with other
measurements. The main problem is that the interrupt function might run more
time stamps to the faster measurements in order to allow normal data analysis.
To enable the interrupt facility on the SDM-CAN you need to index (--) the
program on the number-of-bits parameter (10) of the particular P118 instruction
that you want to cause the interrupt when data is received. The following rules
apply:
3-13
SDM-CAN CAN-Bus Interface User Guide
•
The interrupt function only applies to data types which read data from the
CAN-Bus.
•
You can mark more than one P118 instruction to generate an interrupt, but
you will then need to read data from all the possible data types which are
indexed, as one or more may contain a new value and all new data must be
read before the interrupt is cleared.
•
With the CR10X and CR23X dataloggers you should ensure that all of the
P118 instructions which are marked to cause an interrupt are in the same
interrupt subroutine, normally number 98. Other dataloggers do not currently
support the interrupt subroutine mechanism, but can be used in a similar mode
by polling the digital input connected to the SDM-CAN I/O port, and only
actually reading the data when the port is high.
As well as indexing parameter 10 of the instructions, you also have to enable the
interrupt function by changing an internal software ‘switch’ in the SDM-CAN.
This is done by calling P118 with data type 32, and setting digit ‘c’ to 1 or 2. (See
above).
A switch value of 1 causes the interrupt function to operate in the following way:
a)
With no Interrupt pending the I/O port is pulled low with 100Kohms.
b) With an interrupt pending, i.e. data has been captured, the SDM-CAN will
first check that no other device is holding the port high and then pulse high
for 50 milliseconds. If the I/O terminal is held at +5V by another peripheral it
will wait until the I/O terminal goes low and has been low for 50 milliseconds
before trying to drive it high to +5V again. The I/O line has a drive
impedance of 1Kohms.
This method of driving the I/O line allows multiple SDM-CANs and other CSL
products that support the I/O line to be wired in parallel. One consequence of the
above technique, though, is that there will be a gap of up to 50 milliseconds
following the end of one interrupt before the SDM-CAN will raise the port for
another interrupt. This could be a limitation in high speed data capture
applications, hence the need for switch 2.
When switch 2 is set, the SDM-CAN responds immediately to data receipt and
raises the port as soon as data has been received, filtered and processed. The
SDM-CAN will only lower the line again permanently when the datalogger reads
the data out of the SDM-CAN that caused the interrupt. To prevent problems with
some events which might cause the datalogger to miss interrupts, the SDM-CAN
will pulse the I/O port low for 1 ms after 50 ms, take the line high and then repeat
this cycle until all the relevant data has been read. Using this switch setting will
provide the quickest way of capturing data but may not work with other devices
sharing the datalogger interrupt port.
NOTE
3-14
To ensure proper configuration of the SDM-CAN by the datalogger
for interrupt driven applications, it will pulse its I/O port on and off
at 50ms intervals for 6 seconds after power-up or program
recompilation.
Section 3. Programming CR10X, CR7 and CR23X
3.4.2 Group Trigger
The group trigger function provides a mechanism to synchronise the data capture
by one or more SDM-CAN (and some other SDM devices too).
This mode is enabled when an SDM-Group Trigger (P110) instruction is
encountered. When this instruction runs, it broadcasts a special SDM message
which causes all the SDM-CAN devices to copy the last data values captured from
the CAN-bus into the working data buffers, and no further updates are allowed
until P110 runs again (normally at the next execution of the program table). P118
instructions will read the locked values which are all sampled at once.
This SDM-Group trigger command is normally positioned at the beginning of the
program table to lock all data samples exactly to the start of the scan interval. It
should be remembered, however, that in the case of the SDM-CAN it will simply
lock these values to the last values captured which could already have been
transmitted some time earlier.
The SDM-Group trigger instruction actually broadcasts its message to SDM
address 334 (base 4), which prevents this address being available if the SDMGroup trigger command is to be used. This effectively reduces the number of
SDM peripherals that support global trigger to 15 units.
3.4.3 Frame buffers with filtering and triggering
Operating systems V3 include the ability for the user data logger program to
attach a buffer of 256 frames to any receiving CAN ID up to a limit of 25 different
ID’s.
NOTE
If the user program tries to allocate more than 25 buffers then
the additional buffer allocations will be ignored.
Each buffer can be configured as a standard ring buffer with no trigger or filter
associated with it. The buffer can also be set to start to capture data when a
predefined trigger pattern is encountered within the CAN data, or it can filter and
buffer only the CAN frames that have some part of the data that fits a pattern.
To configure a filter or trigger two masks are used. The first is user defined as a 64
bit include AND mask applied to the CAN data of the CAN ID of interest. A
second 64 bit user defined pattern is compared with the CAN data and when it
matches the results of the previous `AND’ operation the buffer will either trigger
or filter CAN data of a specific ID until the buffer is full.
The buffer is a fill and stop ring buffer so if the buffer is full no more data will be
stored until the logger reads a frame and makes room for another frame to be
stored. With no mask and pattern bits set in trigger mode the buffer will trigger on
any frame and behave as a normal ring buffer. This is useful for collecting fast
back to back bursts of packets as the logger can collect them later in the
knowledge the SDM-CAN will have captured up to 256 packets and stored them
in its buffer.
3-15
SDM-CAN CAN-Bus Interface User Guide
Setup of Mask and Filter / trigger
To implement this buffer function the build data frame Data type (7) is used as
follows:a)
If “start bit number” (parameter 9) is NON-zero then data type 7 will build a
data frame as normal.
b)
If (parameter 9) is zero, the number of bits (parameter 10) is set to 8 with
index (--) NOT SET and number of bytes (parameter 11) is set to 16 then an
`Include mask’ and `Filter mask’ can be set at run time. The first 8 bytes are
the Include mask mapped directly as a 64 bit frame with the first byte as the
right most byte of the data frame. The second 8 bytes is the Filter mask
mapped directly as a 64 bit frame with the first byte as the right most byte of
the data frame. This instruction will also flush the buffer. This is used to
create the buffer and attach it to a particular ID.
s
c)
If (parameter 9) is zero, the number of bits (parameter 10) is set to 8 with the
index (--) SET and number of bytes (parameter 11) is set to 16 then an
`Include mask’ and `Trigger mask’ can be set at run time. The first 8 bytes
are the Include mask mapped directly as a 64 bit frame with the first byte as
the right most byte of the data frame. The second 8 bytes is the Trigger mask
mapped directly as a 64 bit frame with the first byte as the right most byte of
the data frame. This instruction will also flush the buffer and reset ready for
trigger. This is used to create the buffer and attach it to a particular ID.
Reading / Polling Buffer
To implement this buffer function the read switch Data type (33) is used as
follows: a)
If “start bit number” (parameter 9) is zero then data type 33 will read the
internal switches as normal.
b)
If (parameter 9) is one, the number of bits (parameter 10) is set to 8 with the
index (--) NOT SET and number of bytes (parameter 11) is set to zero then
one CAN frame will be transferred from the buffer to the working buffer
ready for normal data collection using Data Types 1-6. Also the number of
CAN frames stored in the buffer will be stored in a logger location specified
by this instruction.
c)
If (parameter 9) is one, number of bits (parameter 10) is set to 8 with the
index (--) SET and number of bytes (parameter 11) is set to zero then only
the number of CAN frames stored in the buffer will be stored in a logger
location specified by this instruction. This instruction would generally be
used for polling the buffer.
Basic Sequence of Buffer Usage:-
3-16
1.
Initialise buffer and trigger event or filter using an SDM-CAN instruction
with data type 7.
2.
Wait long enough or poll the buffer until enough CAN frames are
collected using an SDM-CAN instruction with data type 33.
3.
Transfer a CAN frame from the buffer to the working buffer using an
SDN-CAN instruction with data type 33.
4.
Parse the CAN data frame using the normal SDM-CAN data types 1-6.
5.
Repeat from (3) until you have collected and parsed all the CAN frames
you require from the buffer.
6.
Do other processing ………..
7.
Repeat from (1) to collect another set of CAN frames.
Section 3. Programming CR10X, CR7 and CR23X
3.5 Program Examples
Examples of specific instructions which decode/encode CAN data are shown in
Appendix C. This section gives some general examples of program constructs
which show the general principles of operation.
3.5.1 Reading CAN Data
The following example reads a 16 bit engine speed value from a CAN network
running at 250K baud.
;{CR23X}
;
*Table 1 Program
01: 1.0
Execution Interval (seconds)
;Retrieve Data from CAN network
1:
1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
SDM-CAN (P118)
0
SDM Address
4
Time Quanta
5
Tseg1
2
Tseg2
1024
ID Bits 0..10 (-- for 11-bit CAN ID)
7680
ID Bits 11..23
12
ID Bits 24..28
2
Rx, unsigned int, LSB 1st
33
Start Bit No.
16
No. of Bits
1
No. of Values
1
Loc [ Eng_Spd
]
0.125
Mult
0.0
Offset
*Table 2 Program
02: 0.0000
Execution Interval (seconds)
*Table 3 Subroutines
End Program
NOTE
The above example uses the J1939 standard to define the ID
parameter and value position in the data frame. Please refer to
Appendix C for an explanation of the application of the SDM-CAN
interface to networks complying to the J1939 standard.
3-17
SDM-CAN CAN-Bus Interface User Guide
3.5.2 Simple CAN Data Transmission
The following example transmits a 16 bit temperature value to a CAN network
running at 500K baud.
;{CR10X}
;
*Table 1 Program
01: 1
Execution Interval (seconds)
;When Flag 1 is high set SDM-CAN switches to transmit mode
1: If Flag/Port (P91)
1: 11
Do if Flag 1 is High
2: 30
Then Do
;Load input location with value for switches
6:
1:
2:
3:
Z=F (P30)
0003
F
0
Exponent of 10
3
Z Loc [ Switches
]
;Send switch settings to SDM-CAN
7:
1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
SDM-CAN (P118)
0
SDM Address
2
Time Quanta
5
Tseg1
2
Tseg2
1
ID Bits 0..10
0
ID Bits 11..23
0
ID Bits 24..28
32
Set switches
00
Start Bit No.
00
No. of Bits
00
No. of Values
3
Loc [ Switches
1.0
Mult
0.0
Offset
]
;Set flag 1 low after sending switch settings
8: Do (P86)
1: 21
Set Flag 1 Low
9: End (P95)
10: Batt Voltage (P10)
1: 4
Loc [ Battery
]
11: Internal Temperature (P17)
1: 5
Loc [ Int_Temp ]
12:
1:
2:
3:
4:
5:
3-18
Thermocouple Temp (DIFF) (P14)
6
Reps
1
2.5 mV Slow Range
1
DIFF Channel
1
Type T (Copper-Constantan)
5
Ref Temp (Deg. C) Loc [ Int_Temp
]
Section 3. Programming CR10X, CR7 and CR23X
6: 6
7: 1.0
8: 0.0
Loc [ TC_1
Mult
Offset
]
;Transmit Data on to CAN network
13:
1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
SDM-CAN
0
2
5
2
1
0
0
20
1
16
1
6
1.0
0.0
(P118)
SDM Address
Time Quanta
Tseg1
Tseg2
ID Bits 0..10
ID Bits 11..23
ID Bits 24..28
Tx, unsigned int, LSB 1st
Start Bit No.
No. of Bits
No. of Values
Loc [ TC_1
]
Mult
Offset
*Table 2 Program
02: 0.0000
Execution Interval (seconds)
*Table 3 Subroutines
End Program
NOTE
The default setting for the SDM-CAN internal software switches is
0. The switches must be set by using the data type 32 parameter to
enable data transmission. Also remember to check the jumper
settings inside the SDM-CAN if enabling transmission, as the
default setting is for transmission to be disabled in hardware.
3.5.3 Building and Sending Data Frames
The following table shows the parameters used for the process of using a series of
P118s to build a dataframe and then use a further call with data type set to 26 to
define part of the working buffer as a remote frame response:
Input Loc Value
Dec
Data
type
Start Bit
Hex
nbits
Indexed
64 bit Frame
Un-initialised frame>>
0x12abcdef12345678
170
0xaa
7
5
N
8
Loaded into frame>>
0x0000000000000aa0
1234
0x4d2
13
17
N
16
Ored into frame>>
0x0000000004d20aa0
65535
0xffff
13
31
N
7
Ored into frame>>
0x0000001fc4d20aa0
171
0xab
13
8
Y
8
Ored into frame>>
0xab00001fc4d20aa0
X
X
26
28
Y
32
Remote Response Frame>>
0x0ab00001 32 bit frame
3-19
SDM-CAN CAN-Bus Interface User Guide
3.5.4 Using the Interrupt Function
By indexing (‘--‘) the No. of bits parameter, when a new value that an instruction
refers to is received the SDM-CAN I/O interrupt is enabled. This can be used to
set a control port high and run an interrupt subroutine. An example of using the
interrupt function is shown below.
;{CR23X}
;
*Table 1 Program
01: 1
Execution Interval (seconds)
;Set flag 1 high to set SDM-CAN internal software switches
1: If Flag/Port (P91)
1: 11
Do if Flag 1 is High
2: 30
Then Do
;Load input location with value for switches
2:
1:
2:
3:
Z=F (P30)
10
F
0
Exponent of 10
3
Z Loc [ Switches
]
;Send switch settings to SDM-CAN
3:
1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
SDM-CAN (P118)
0
SDM Address
2
Time Quanta
5
Tseg1
2
Tseg2
1
ID Bits 0..10
0
ID Bits 11..23
0
ID Bits 24..28
32
Set switches
00
Start Bit No.
00
No. of Bits
00
No. of Values
3
Loc [ Switches
1.0
Mult
0.0
Offset
]
;Set flag 1 low after sending switch settings
4: Do (P86)
1: 21
Set Flag 1 Low
5:
End (P95)
*Table 2 Program
02: 0.0000
Execution Interval (seconds)
*Table 3 Subroutines
3-20
Section 3. Programming CR10X, CR7 and CR23X
;Interrupt subroutine 98, when C8 goes high run this subroutine
1: Beginning of Subroutine (P85)
1: 98
Subroutine 98
;Read CAN value
2:
1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
SDM-CAN (P118)
00
SDM Address
2
Time Quanta
5
Tseg1
2
Tseg2
1
ID Bits 0..10 (-- for 11-bit CAN ID)
0
ID Bits 11..23
0
ID Bits 24..28
1
Rx, unsigned int, MSB 1st
1
Start Bit No.
16
-- No. of Bits
1
No. of Values
10
Loc [ RxTC_1
]
1.0
Mult
0.0
Offset
;end of interrupt subroutine
3:
End (P95)
End Program
3.5.5 Using the Group Trigger
The SDM-Group Trigger controls SDM devices that support the Group Trigger
protocol, including the SDM-CAN. All Group Trigger devices are triggered to
make simultaneous measurements, the data is then retrieved by using the
appropriate instruction.
For the SDM-CAN, this instruction is can be used in a vehicle where more than
one CANbus network is present. An example of using the group trigger is shown
below.
;{CR23X}
;
*Table 1 Program
01: 1
Execution Interval (seconds)
;Initiate Group Trigger
1:
SDM-Group Trigger (P110)
;Retrieve Data from CAN network A
2:
1:
2:
3:
4:
5:
6:
SDM-CAN (P118)
00
SDM Address
4
Time Quanta
5
Tseg1
2
Tseg2
204
ID Bits 0..10 (-- for 11-bit CAN ID)
81 1
ID Bits 11..23
3-21
SDM-CAN CAN-Bus Interface User Guide
7:
8:
9:
10:
11:
12:
13:
14:
7
23
1
32
1
1
1.0
0.0
ID Bits 24..28
Tx, real IEEE4, MSB 1st
Start Bit No.
No. of Bits
No. of Values
Loc [ AC_Comp_1 ]
Mult
Offset
;Retrieve Data from CAN network B
3:
1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
SDM-CAN (P118)
01
SDM Address
4
Time Quanta
5
Tseg1
2
Tseg2
1024
ID Bits 0..10 (-- for 11-bit CAN ID)
7680
ID Bits 11..23
12
ID Bits 24..28
2
Rx, unsigned int, LSB 1st
33
Start Bit No.
16
No. of Bits
1
No. of Values
2
Loc [ Eng_1
]
0.125
Mult
0.0
Offset
;Retrieve Data from CAN network B
8:
1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
SDM-CAN (P118)
01
SDM Address
4
Time Quanta
5
Tseg1
2
Tseg2
768
ID Bits 0..10 (-- for 11-bit CAN ID)
7680
ID Bits 11..23
12
ID Bits 24..28
1
Rx, unsigned int, MSB 1st
49
Start Bit No.
8
No. of Bits
1
No. of Values
3
Loc [ Throttl_1 ]
0.125
Mult
0.0
Offset
*Table 2 Program
02: 0.0000
Execution Interval (seconds)
*Table 3 Subroutines
End Program
3-22
Section 4. Programming CRBasic
Dataloggers to use the SDM-CAN
This chapter describes how to program the CR5000/CR9000X and older CR9000 dataloggers,
using CRBASIC language, to control the SDM-CAN interface. Similar principles can be
followed for newer CRX000 dataloggers that include the SDM-CAN instruction in their
operating system.
4.1 General Principles
Some newer dataloggers use the CRBASIC programming language. CRBASIC
incorporates an instruction which is virtually identical to P118, described in
Section 3. To avoid duplication this section of the manual simply references the
relevant paragraphs in that section. For this reason you are advised to read section
three in its entirety to gain a full understanding of all the general principles and
parameter settings.
Currently neither the CR5000, CR9000X nor CR9000 support interrupt driven
events as described above. However, with the extra speed of these dataloggers, a
similar function can be achieved by polling a digital input and only executing the
instructions required when the port is high. The consequences of doing this in
either the slow or fast tables needs to be considered, especially when trying to
synchronise this data with analogue measurements.
4.1.1 High Speed Block Mode
Operating system Version 3 supports a new high speed block mode for SDM
communication that allows much faster data transfers to the logger. This was
implemented for the CR9000 and CR5000 to allow users to run a program at more
than 200Hz with the SDM-CAN. It gives a 5 fold improvement in performance
over normal mode. Block mode operation is activated by using data types 65 to
70; these are the block mode equivalents of data type’s 1 to 6. When block mode
is active then all CAN data is collected at the beginning of the scan in parallel
with analogue measurements. There are a number of restrictions when using block
mode. There is a limit of 128 values that can be read in total. Other restrictions are
logger specific. On a CR9000 - firstly you can only have one differently addressed
SDM-CAN in each scan unless all other differently addressed SDM-CAN’s are
using normal mode data types 1 to 6. Secondly you cannot use conditional
statements with SDM-CAN instructions which are enabled for block mode.
Restrictions for use with the CR9000X/CR5000 are that you must keep all block
mode instructions together and not intermix normal mode instructions within the
group of block mode instructions. You can however put normal mode instructions
in front or after the group of block mode instructions. You cannot use conditional
statements on either normal or block mode SDM-CAN instructions.
Time to execute block mode for a CR9000 in milliseconds with maximum bus
speed `SDMSpeed(0)’ is approximately = 1.50 + 0.1 * n bytes of data.
Time to execute block mode for a CR9000 in milliseconds with default bus speed
is approximately = 2.07 + 0.207 * n bytes of data.
Time to execute block mode for a CR5000 in milliseconds with maximum bus
speed `SDMSpeed(12)’ is approximately = 1.60 + 0.108 * n bytes of data.
4-1
SDM-CAN CAN-Bus Interface User Guide
Time to execute block mode for a CR5000 in milliseconds with default bus speed
is approximately = 2.12 + 0.27 * n bytes of data.
This timing is only for the block mode instruction and any other instructions
within the scan will reduce the maximum possible scan rate.
4.2 Datalogger Instruction
The SDM-CAN is controlled by an instruction called CANBUS. Please check that
your datalogger’s operating system includes this instruction. You may also require
an update to your CRBASIC editor to get the full help screens. Contact Campbell
Scientific if you need advice about upgrading your operating system.
The CANBUS instruction takes the form:
CANBUS(CANDATA(),ADDRESS,TIMEQUANTA,TSEG1,TSEG2,ID,
DATATYPE,STARTBIT,NUMBITS,NUMVALS,MULT,OFFSET)
where:
CANDATA is a variable or array which either holds data to be transmitted or will
hold data that is to be read from the CAN-Bus.
ADDRESS is the SDM address of the SDM-CAN in question.
TQUANTA, TSEG1 and TSEG2 have the same function as in P118 above.
ID is the CAN ID, where the ID is entered as a single decimal equivalent.
Entering the number as a negative value signifies it is an 11 bit ID, otherwise it is
a 29-bit ID.
NOTE
Due to current system constraints the ID parameter must be entered
directly into the CanBus instruction.
DATATYPE is the same as in P118.
STARTBIT is the same as in P118, except you enter a negative number instead of
‘indexing’ the number to signify lefthand referencing.
NUMBITS is the same, and again a negative number is equivalent to indexing the
value to enable an interrupt.
NUMVALS, MULT and OFFSET all have the same function.
4-2
Section 4. Programming the CR9000 and CR5000
4.2.1 Reading CAN Data
The following example reads a 16 bit engine speed value from a CAN network
running at 250K baud.
'Set scan rate
Const PERIOD = 1
Const P_UNITS = 2
'Scan interval number
'Scan interval units (Secs)
'\\\\\\\\\\\\\\\\\\\\\\\\\ CANBUS CONSTANTS //////////////////////
'------------------- Physical Network Parameters ----------------Const TQUANT = 4
Const TSEG1 = 5
Const TSEG2 = 2
')Set SDM-CAN to 250K
')Network speed
')
'---------------------- Data Frame Parameters -------------------'___________________________CANbus Block1_________________________
'Collect and retrieve 16 bit data value
'Data type 2, unsigned integer, least significant byte first
Const CANREP1 = 1
Const ADDR1 = 0
Const DTYPE1 = 2
Const STBIT1 = 33
Const NBITS1 = 16
Const NVALS1 = 1
Const CMULT1 = 0.4
Const COSET1 = 0
Dim CANBlk1(CANREP1)
'Repetitions
'SDM address of SDM-CAN Module
'Collect and retrieve data values
'Start position in data frame
'Number of bits/value
'Number of values
'Multiplier
'Offset
'Dimensioned source
'\\\\\\\\\\\\\\\\\\ ALIASES & OTHER VARIABLES //////////////////
Alias CANBlk1(1) = Engine_Speed
'Assign an alias name to CANBlk1(1)
'\\\\\\\\\\\\\\\\\\\\\\\\\\\ PROGRAM ///////////////////////////
BeginProg
'MainSequence
Scan(PERIOD,P_UNITS,0,0)
'Program begins here
'Scan once every 1 Secs, non-burst
'__________________________ CAN Blocks __________________________
'Retrieve Data from CAN network
CanBus(CANBlk1(),ADDR1,TQUANT,TSEG1,TSEG2,217056256,
DTYPE1,STBIT1,NBITS1,NVALS1,CMULT1,COSET1)
Next Scan
'Loop up for the next scan
EndProg
'Program ends here
4-3
SDM-CAN CAN-Bus Interface User Guide
4.2.2 Simple CAN Data Transmission
The following example transmits a 16 bit temperature value to a CAN network
running at 250K baud.
'Set scan rate
Const PERIOD = 1
Const P_UNITS = 2
'Scan interval number
'Scan interval units (Secs)
\\\\\\\\\\\\\\\\\\\\ THERMOCOUPLE CONSTANTS ////////////////////
'__________________________ Temp Block1 __________________________
Const TRNG1 = 17
Const TTYPE1 = 0
Const TREP1 = 1
Const TSETL1 = 30
Const TINT1 = 20000
Const TMULT1 = 1
Const TOSET1 = 0
Dim TBlk1(TREP1)
Units TBlk1 = Deg_C
'Block1
'Block1
'Block1
'Block1
'Block1
'Block1
'Block1
'Block1
'Block1
measurement range (50 mV)
thermocouple type (T)
repetitions
settling time (usecs)
integration time (usecs)
default multiplier
default offset
dimensioned source
default units (Deg_C)
'\\\\\\\\\\\\\\\\\\\\\\\\\ CANBUS CONSTANTS //////////////////////
'------------------- Physical Network Parameters ----------------Const TQUANT = 4
Const TSEG1 = 5
Const TSEG2 = 2
')Set SDM-CAN to 250K
')Network speed
')
'---------------------- Data Frame Parameters -------------------'___________________________CANbus Block1_________________________
'Send switch value Data type 32
Const CANREP1 = 1
Const ADDR1 = 0
Const DTYPE1 = 32
Const STBIT1 = 0
Const NBITS1 = 0
Const NVALS1 = 0
Const CMULT1 = 1.0
Const COSET1 = 0
Dim Switches(CANREP1)
'Repetitions
'SDM address of SDM-CAN Module
'Send switch value
'Start position in data frame
'Number of bits/value
'Number of values
'Multiplier
'Offset
'Dimensioned source
'___________________________CANbus Block2_________________________
'Transmit 16 bit data value
'Data type 20, unsigned integer, least significant byte first
Const
Const
Const
Const
Const
Const
Const
Const
4-4
CANREP2 = 1
ADDRESS2 = 0
DTYPE2 = 20
STBIT2 = 49
NBITS2 = 16
NVALS2 = 1
CMULT2 = 1
COSET2 = 0
'Repetitions
'SDM address of SDM-CAN Module
'Tx, unsigned int, LSB 1st
'Start position in data frame
'Number of bits/value
'Number of values
'Multiplier
'Offset
Section 4. Programming the CR9000 and CR5000
'\\\\\\\\\\\\\\\\\\ ALIASES & OTHER VARIABLES //////////////////
Public Flag(8)
Dim TRef(1)
'General Purpose Flags
'Declare Reference Temp variable
'\\\\\\\\\\\\\\\\\\\\\\\\\\\ PROGRAM ///////////////////////////
BeginProg
'MainSequence
Scan(PERIOD,P_UNITS,0,0)
'Program begins here
'Scan once every 1 Secs, non-burst
'__________________________ Temp Blocks __________________________
ModuleTemp(TRef(),1,5,100)
TCSE(TBlk1(),TREP1,TRNG1,5,1,TTYPE1,TRef(1),
TSETL1,TINT1,TMULT1,TOSET1)
'__________________________ CAN Blocks __________________________
'When Flag 1 is high set SDM-CAN switches to transmit mode
If Flag(1) Then
'Load variable with value for switches
Switches = 3
'Send switch settings to SDM-CAN
CanBus(Switches,ADDR1,TQUANT,TSEG1,TSEG2,0,
DTYPE1,STBIT1,NBITS1,NVALS1,CMULT1,COSET1)
'Set flag 1 low after sending switch settings
Flag(1) = False
EndIf
'Transmit Data on to CAN network
CanBus(TBlk1(),ADDR2,TQUANT,TSEG1,TSEG2,1,
DTYPE2,STBIT2,NBITS2,NVALS2,CMULT2,COSET2)
Next Scan
'Loop up for the next scan
EndProg
'Program ends here
NOTE
The default setting for the SDM-CAN internal software switches is
0. The switches must be set by using the data type 32 parameter to
enable data transmission. Also remember to check the jumper
settings inside the SDM-CAN if enabling transmission, as the
default setting is for transmission to be disabled in hardware.
4.2.3 Digital I/O Triggered CANbus Measurements
Although the CR5000 and CR9000 do not have the interrupt feature that is
available on the CR10X, CR7 and CR23X it is possible to connect the I/O line
from the SDM-CAN to a Digital I/O port. A program control instruction can then
be used to trigger the retrieval of new CAN data from the SDM-CAN when the
port is high. An example of this is shown below
'Set scan rate
Const PERIOD = 1
Const P_UNITS = 2
'Scan interval number
'Scan interval units (Secs)
4-5
SDM-CAN CAN-Bus Interface User Guide
'\\\\\\\\\\\\\\\\\\\\\\\\\ CANBUS CONSTANTS //////////////////////
'------------------- Physical Network Parameters ----------------Const TQUANTA = 4
Const TSEG1 = 5
Const TSEG2 = 2
')Set SDM-CAN to 250K
')Network speed
')
'---------------------- Data Frame Parameters -------------------'___________________________CANbus Block1_________________________
Const CANREP1 = 1
Const ADDRESS1 = 0
Const DATATYPE1 = 1
Const STARTBIT1 = 1
Const NUMBITS1 = -16
Const NUMVALS1 = 1
Dim CANBlk1(CANREP1)
Dim NewData
'Repetitions
'SDM address of SDM-CAN Module
'Collect and retrieve data values
'Start position in data frame
'Number of bits/value – for interrupt
'Number of values
'Dimensioned source
'\\\\\\\\\\\\\\\\\\ ALIASES & OTHER VARIABLES //////////////////
Alias CANBlk1(1) = Accel_Pedal
'Assign an alias name to CANBlk1(1)
'\\\\\\\\\\\\\\\\\\\\\\\\\\\ PROGRAM ///////////////////////////
BeginProg
'MainSequence
Scan(PERIOD,P_UNITS,0,0)
'Program begins here
'Scan once every 1 Secs, non-burst
'__________________________ CAN Blocks __________________________
'Read status of digital I/O port, return value to NewData variable
ReadIO(NewData,7,&B1)
'When digital I/O port is high retrieve data from CAN network
If NewData > 0 Then
CanBus(CANBlk1(),ADDRESS1,TQUANTA,TSEG1,TSEG2, 217056000,
DATATYPE1,STARTBIT1,NUMBITS1,NUMVALS1,1,0)
EndIf
Next Scan
'Loop up for the next scan
EndProg
'Program ends here
NOTE
Due to current system constraints the ID parameter must be entered
directly into the CanBus instruction.
4.2.4 SlowSequence Instruction
It is also possible to have a SlowSequence Scan for low priority CANbus
measurements that are not needed at the rate of the primary scan interval. The
CR9000 or CR5000 tags on measurement instructions from the slow sequence
scan to the normal scan as time allows.
Please refer to the CR9000 or CR5000 on-line help for a more detailed
explanation of the SlowSequence instruction.
4-6
Section 5. Using the RS232 Serial
Diagnostics Port
5.1 Connecting to the RS232 User Port
The user communication port is a DCE configured, 9 pin RS232 port. The port
automatically powers up when it detects valid RS232 signals and shuts down after
a period of inactivity. The SDM-CAN automatically detects the incoming baud
rates in the range from 1200 to 115200 baud. It is configured to work with eight
data bits, one start bit and stop bit and no parity. The pin out of the RS232 DCE 9
pin ‘D’ plug is shown in Table 5-1.
Table 5-1 RS232 Pin Out
Pin Number
RS232 function
Direction of signal
1
DCD
input.
2
RX
input.
3
TX
Output.
4
DTR
Output.
5
0V
Ground.
6
DSR
input.
7
RTS
Output.
8
CTS
input.
9
RI
input.
To connect the SDM-CAN to most computers use a NULL Modem cable. When
you try to communicate with the SDM-CAN, first send at least three ‘Carriage
Returns’ so the SDM-CAN can recognise the baud rate at which you are
communicating. As soon as your baud rate has been detected, the SDM-CAN will
return the prompt ‘CAN>’ to your terminal window. If you have just powered the
SDM-CAN up, you must wait until the LED status flash has finished before you
attempt to communicate.
The User Command interface will accept a number of commands which allow the
user to view CAN frames, view set-up and other debug tools. These commands
are discussed below.
5.2 Diagnostic Commands
Most commands are sent in normal ASCII text. The interface is not case sensitive
and supports backspace for correction of typing errors. Normally you would
execute these commands from a PC which is running a terminal emulator such as
Hyperterminal.
Some parameters for the commands are normally entered in decimal base 10
format, but you can also enter them in hex format if you precede the number with
‘0x’. For example, 12345610 can be entered ‘as it is’ or, alternatively, in hex
format 0x1e24016.
5-1
SDM-CAN CAN-Bus Interface User Guide
The diagnostic commands are listed below:
BINS – This command will cause a hex dump of the bins configured by the
datalogger program. The output for each line is as follows:
Bin number, Data type, Start bit, Number of bits, Buffer pointer, Bin flags,
Number of values, TQUANTA, TSEG1, TSEG2, SDM mode and CAN ID.
These fields are in raw format and may contain flags to indicate modes.
This command is used by Campbell Scientific for diagnostic purposes only.
BUFFERS – Takes no parameters. This command will dump the buffers
configured by the datalogger program.
The output format is:
On the first line after the command, the number of buffers used in shown in hex
format, then on each successive line the buffer set-up is dumped in the following
hex form: Buffer Number, Frame ID, Info Byte, Flags, Working Buffer, Read
Buffer, Bin Number Pointer. This command is only normally used by Campbell
Scientific for diagnostic purposes.
CANBAUD nnnn – Scans the CANBUS to attempt to ascertain the current baud
rate. Parameter 'n' is in the range of 0-255 and is the amount of time, in steps of
50ms, the SDM-CAN should dwell at each baud rate looking for CANBUS
activity. If the 'n' parameter is omitted, two seconds dwell time will be used by
default.
The CANBUS is scanned for the following baud rates:
20K, 50K, 125K, 250K, 500K, 800K and 1 Megabaud.
As soon as the baud rate is found, the bus parameters TQUANTA, TESG1,
TSEG2 and frames / n*50msec are reported to the user. The SDM-CAN will then
be set to, and stay at, this baud rate until the changed by the datalogger following a
re-compilation of the program by the user, or by a datalogger SDM
communications error which will force the SDM-CAN to be reset. If no baud rate
can be detected, an error is reported to the user.
Because any communication errors cause a default back to the datalogger set baud
rate, it is not recommended that this command is used for anything other than
CANBUS diagnostic purposes.
CLRERROR – Takes no parameters. This command will clear all the error
counters Transmit, Receive, Overrun and Watch-dog to zero and clear a bus off
condition.
COMP – Takes no parameters. This command will force the datalogger to resend all of the configuration information again. This command is used by
Campbell Scientific for debugging purposes only.
HELP or ? – Prints a list of valid user commands.
HEXDUMP aaaa bbbb – The first parameter ‘aaaa’ is the start address and the
second parameter ‘bbbb’ is the number of bytes to dump. This command will
dump the SDM-CAN’s full memory address range in a hex format. Each line that
is output starts with the address followed by a16 byte value and then the ASCII
characters. Any unprintable characters are represented by a ‘.’ character.
MONITOR nnnn – This command takes parameters in the range n=0 to n=2,
where:
0 = monitor CANBUS for IDs used by the datalogger program (this is the default
if the parameter is missing).
1 = monitor CANBUS for IDs that are allowed to pass through the simple IDfilter.
2 = monitor all CANBUS messages on the bus.
The monitor command will output a CAN frame in hex format when received.
This command has a ring buffer that can hold 20 frames before it overflows.
5-2
Section 5. Using the RS232 Diagnostics Port
Monitor mode will not miss frames when they come in high speed burst’s. This
command will perform better the higher the terminal baud rate.
The hex output format of the command is as follows:- Info byte, Frame ID, Frame
Data. To exit this command use ‘CTRL-C’.
SETCANBAUD nnnn nnnn nnnn – Sets the CANBUS baud rate. The
parameters are in the following order: TQUANTA = 0 - 63, TSEG1 = 0 - 15 and
TSEG2 = 0 to 7. See Section 3 which gives details on how to calculate baud rate
using these parameters. The SDM-CAN baud rate will stay set until it is changed
by the datalogger following a program re-compilation by the user, or by a
datalogger communications error, which will force the SDM-CAN to be reset.
If parameters are omitted, the default setting is 1 Megabaud with the following
parameters: TQUANTA=1, TSEG1=5 and TSEG2=2.
Because any communication errors cause a default back to the datalogger set baud
rate, it is not recommended that this command is used for anything other than
CANBUS diagnostic purposes.
STAT – Takes no parameters. This command will return the CAN bus status as
follows (each value is output on a new line in decimal format):
TQUANTA, TSEG1, TSEG2, Transmit error, Receive error, Overrun error,
Watchdog error, Switch Settings, SDM Address, verbose mode, Bus mode and
buffers = n n n where the first `n’ is number of bins, the 2nd `n’ is number of
buffers and the 3rd `n’ is number of frame buffers.
Bus mode indicates the following states:
0=Bus-On; the SDM-CAN is involved in bus activities. Error counters are less
than 96.
1=Bus-On; the SDM-CAN is involved in bus activities. Error counters are equal to
or greater than 96.
2=Bus-Off; the SDM-CAN is not involved in bus activities. Error counters are less
than 96.
3=Bus-Off; the SDM-CAN is not involved in bus activities. Error counters are
equal to or greater than 96.
SWITCH nnnn – This command changes the internal switch settings of the
SDM-CAN. Please refer to Data type 32, in section 3 above, for details of the
switch parameter.
VERBOSE nnnn – The parameter nnnn is the verbose mode. With no parameter
or when nnnn=0 verbose mode is off, otherwise if nnnn>0 verbose mode is on.
Currently verbose mode ‘1’ turns on compile reports – used for Campbell
Scientific debugging purposes only.
VERSION – Takes no parameters. This command will output the OS version
number on the first line and the OS signature on the second line. If the signature is
zero then the OS is corrupt and the SDM-CAN may malfunction. The Status is
then returned (see STAT above).
5.3 Loading a New Operating System into the
SDM-CAN Interface
When new functions are added, or bugs fixed, new versions of the operating
system for the SDM-CAN interface may become available. As with most newer
Campbell Scientific devices, the operating system is stored in non-volatile
memory which can be re-programmed or updated by downloading a new
operating system to the module from a PC running appropriate Campbell
Scientific software (see below).
5-3
SDM-CAN CAN-Bus Interface User Guide
For downloading software you will need the following:
•
A recent copy of Campbell Scientific’s CSOS operating system download
program
•
A copy of the SDM-CAN operating system (copied to your hard-disk)
•
A PC running Microsoft Windows
•
A serial cable (as described above).
The SDM-CAN also requires a 12V power supply, but does not have to be
connected to a datalogger.
To load the new operating system take the following steps:
5-4
•
Run the CSOS software and set up the communications parameters to specify
the COM port to which the SDM-CAN is connected.
•
Select the file containing the new operating system and then follow the
instructions given. This will normally involve following a sequence of turning
the module off and then on whilst starting the download process from the PC.
•
Wait until the process has completely finished and reports a successful
upgrade before removing power from the SDM-CAN or quitting CSOS.
Appendix A. Principles of Operation
A.1 Data Collection
The SDM-CAN operation is based on a number of sequential buffers. The
hardware has a dedicated CAN controller chip connected to a microprocessor
which analyses and processes the raw CAN data and then transmits it to the
datalogger.
When the CAN-Bus controller receives a good frame first of all it uses its internal
hardware to filter out the frames of no interest to the user. If the frame ID satisfies
the filter requirements then it allows the frame to be transferred to a hardware
FIFO. This FIFO can hold up to 3 CAN frames. Whenever data is in this FIFO an
interrupt mechanism will cause the SDM-CAN processor to read the data from the
CAN controller.
When the processor reads the CAN frame it will do a more detailed check to see if
the CAN frame ID is one of the ones required. This is because the hardware filter
only matches an overall pattern and may let some CAN frames through that are
not required. If the CAN frame ID is accepted, it will then be placed into the
‘Working Buffer’ of a ‘Buffer Set’, which is made up of a set of small buffers in
memory, each set being dedicated to a specific packet ID.
The ‘Buffer Set’ consist of ‘some configuration data’, ‘ID Buffer’, ‘Working
Buffer’ and a ‘Read Buffer’. When the datalogger program is compiled it will
configure the buffers with a specific ID in the ‘ID Buffer’ and also set up the
buffer configuration. Many SDM-CAN instructions may share buffers because the
CAN frame ID and configuration is the same.
Each SDM-CAN instruction will create what is called a BIN within the SDMCAN. This BIN holds information such as which ‘data type’ to use, which ‘Buffer
Set’ it should get the data from and where its ‘New data flag’ is located plus a
large amount of other information.
The ‘New data’ flags are set when new data arrives into the ‘Working Buffer’ of
the ‘Buffer Set’. Because there could be multiple BINs using one ‘Buffer Set’
there will be multiple ‘New data’ flags as well, so all the relevant ‘New data’ flags
will be set at the same time. When the datalogger program reaches a point where it
needs to read the data, the SDM-CAN will first check the ‘New data flag’. If this
flag is clear, the datalogger will read the previous data value unless the switch is
set to detect/prevent multiple reads (see section 3) in which case an over-range
value is read (-99999 on some dataloggers). The SDM-CAN will then clear the
appropriate ‘New data’ flag relevant to the BIN and instruction that requested the
data. Because there is effectively one ‘New data’ flag per call of P118 this means
that you could read the same new data to many different locations. However, you
should be aware that different data could be returned by the different calls of the
instruction, as a new data frame could be captured as the datalogger works through
the program table. This problem can be avoided by using the Global trigger
function.
A.2 Frame Transmission
When the datalogger program is first run it will set-up the SDM-CAN BINs and
buffers. If the program has some P118 instructions that transmit to the CAN-Bus,
then some of the Buffers will be set-up for transmission. When an instruction
indicates that a transmission should take place, the datalogger first sends a BIN
number. This number tells the SDM-CAN which BIN to use and, from the
compile-time set up, what operation is required. In the case of transmission it
would expect frame data to be sent from the datalogger.
A-1
SDM-CAN CAN-Bus Interface User Guide
On receiving the frame data from the datalogger the SDM-CAN will convert and
shift the data into the correct position and then place it into the read buffer which
is set as a 64 bit frame. Depending on your program, you could then continue to
build a frame or decide to transmit it onto the CAN-Bus. If you have completed
the building of a frame then you have the choice to either transmit it onto the
CAN-Bus or set it up as a Remote Frame Response. For the transmitted frames,
the SDM-CAN will set a flag in the buffer to indicate new data is ready for
transmission. The SDM-CAN will scan the buffers, checking this flag in each
buffer that is set for transmission. When it finds a flag that is set, it will first check
if the transmitter is busy, and if it is will wait until it is free. The frame will then
be transferred to the transmitter which will transmit it onto the bus. Finally the
transmit data flag will be cleared.
When a frame is set up for a remote frame response, the frame is transferred into
the working buffer ready for reception of a Remote Frame Request. When a
Remote Frame Request is received, and is accepted as a valid frame, the
SDM-CAN will find the relevant buffer, and will then set the data transmit flag.
From then on it will follow the normal frame transmission protocol as described
above.
A-2
Appendix B. A Summary of Data Types
A summary table of the data types is given below for quick reference.
Data Type Description
1
Retrieve data; unsigned integer, MSB first
2
Retrieve data; unsigned integer, LSB first
3
Retrieve data; signed integer, MSB first
4
Retrieve data; signed integer, LSB first
5
Retrieve data; 4-byte IEEE FP; MSB first
6
Retrieve data; 4-byte IEEE FP; LSB first
7
Build data frame; unsigned integer, MSB first
8
Build data frame; unsigned integer, LSB first
9
Build data frame; signed integer, MSB first
10
Build data frame; signed integer, LSB first
11
Build data frame; 4-byte IEEE FP; MSB first
12
Build data frame; 4-byte IEEE FP; LSB first
13
Build data frame; unsigned integer, MSB first, ‘OR’ed.
14
Build data frame; unsigned integer, LSB first, ‘OR’ed.
15
Build data frame; signed integer, MSB first, ‘OR’ed.
16
Build data frame; signed integer, LSB first, ‘OR’ed.
17
Build data frame; 4-byte IEEE FP; MSB first, ‘OR’ed.
18
Build data frame; 4-byte IEEE FP; LSB first, ‘OR’ed.
19
Transmit data value to the CAN-Bus; unsigned integer, MSB first.
20
Transmit data value to the CAN-Bus; unsigned integer, LSB first.
21
Transmit data value to the CAN-Bus; signed integer, MSB first.
22
Transmit data value to the CAN-Bus; signed integer, LSB first.
23
Transmit data value to the CAN-Bus; 4-byte IEEE FP; MSB first.
24
Transmit data value to the CAN-Bus; 4-byte IEEE FP; LSB first.
25
Transmit previously built data frame to the CAN-Bus.
26
Set up previously built data frame as a Remote Frame Response.
27
Read counters
28
Read counters and reset.
continued
B-1
SDM-CAN CAN-Bus Interface User Guide
29
Read SDM-CAN status
Status Description
0000 The SDM-CAN has bus activities; error counters < 96.
0001 The SDM-CAN has bus activities; at least one error
counter is >= 96.
0002 The SDM-CAN is not involved in bus activities; error
counters < 96.
0003 The SDM-CAN is not involved in bus activities; at least
one error counter >=96.
B-2
30
31
32
Read SDM-CAN operating system and version number
Send Remote Frame Request.
Set SDM-CAN's internal switches
Switch Code Description
A
0
Not used
B
0
returns the last value captured (default)
1
returns –99999 if value already read by
datalogger
C
0
Disable interrupts (default)
1
Enable pulse interrupts
2
Enable fast interrups
3-7
Not defined
8
Place the SDM-CAN into low power
stand-by mode.
9
Leave switch setting unchanged.
D
0
Listen only (error passive) mode.
1
Transmit once.
2
Self-reception.
3
Normal retransmission
4
Transmit once
5
Self-reception; self -test.
6
Normal; self-test.
7
Active at power-up.
8
Not defined.
9
Leave switch setting unchanged.
33
Read SDM-CAN's internal switches (see above)
Appendix C. Application of the
SDM-CAN on Networks Complying with
the J1939 SAE Standards.
This Appendix describes the use of the SDM-CAN in applications where the CAN network
complies to the J1939 standard, which is common in truck, bus and marine applications in the
USA. This appendix is not intended to act as a full reference to those standards, but to simply
describe the coding of the ID parameter and to give examples of how to decode some of the
common, defined J1939 data packets.
C.1 J1939 29-Bit Identifier Format
The J1939 identifier format consists of 6 predefined fields; for a 29-bit identifier
these are:
P - Priority Field (3 bits)
R - Reserved Field (1 bit)
DP - Data Page Field (1 bit)
PF - PDU Format Field (8 bits)
PS - PDU Specific Field (8 bits)
SA - Source Address Field (8 bits)
Table C-1 Mapping of the J1939 Fields into a 29-Bit Identifier
Bit
28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9
8
7
6
5
4
3
2
1
0
P P P R D P P P P P P P P P P P P P P P P S S S S S S S S
3 2 1 1 P F F F F F F F F S S S S S S S S A A A A A A A A
8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1
C.2 J1939 11-Bit Identifier Format
The J1939 identifier format consists of 2 predefined fields; for an 11-bit identifier
these are:
P - Priority Field (3 bits)
SA - Source Address Field (8 bits)
Table C-2 Mapping of the J1939 Fields into a 11-Bit Identifier
Bit
10 9
8
7
6
5
4
3
2
1
0
P P P S S S S S S S S
3 2 1 A A A A A A A A
8 7 6 5 4 3 2 1
NOTE
Details of identifier field values can be found in the SAE J1939
standard.
C-1
SDM-CAN CAN-Bus Interface User Guide
C.3 J1939 Data Frame Format
The Data Frame consists of 8 bytes with byte one at the left side of the frame and
byte eight at the right side. Within each byte, bit 8, the most significant bit is at the
left side of the byte.
NOTE
Multi-byte values are conventionally displayed with the least
significant byte first. For example LSB of engine speed is Byte 4
and MSB is byte 5.
Table C-3 J1939 Data Frame Format
1
2
3
4
5
6
7
8
87654321 87654321 87654321 87654321 87654321 87654321 87654321 87654321
NOTE
Details of specific data frame values can be found in the SAE J1939
standard.
C.4 Retrieving J1939 Accelerator Pedal Position Data
using a CR9000/CR5000 (Bus Speed 250k Baud)
C.4.1 Encoding the Identifier Field Values
The following example shows how to encode the identifier field values into the
format for the CR9000/CR5000 ID parameter.
The identifier field values for the CAN Data Frame are as follows:
Priority
Reserved
Data Page
PDU Format
PDU Specific
Source Address
310
010
010
24010
310
010
These decimal values then need to be converted to binary and encoded into the 29
bit identifier.
C-2
Priority
0112
Reserved
02
Data Page
02
PDU Format
111100002
PDU Specific
000000112
Source Address
000000002
Appendix C. Using SDM-CAN on J1939 Networks
Table C-4 Mapping of J1939 Identifier Field values into a 29-Bit Identifier
Bit
28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9
8
7
6
5
4
3
2
1
0
SOF P P P R D P P P P P P P P P P P P P P P P S S S S S S S S
3 2 1 1 P F F F F F F F F S S S S S S S S A A A A A A A A
8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1
Value 0 1 1 0 0 1 1 1 1 0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 0 0 0 0 0
This gives a binary value of 01100111100000000001100000000 that can then be
converted to 21705600010 and used as the ID parameter.
C.4.2 Finding the Start Bit
The byte number of the Accelerator pedal position value is 2
Table C-5 Accelerator Pedal Position Value Byte Number
1
2
3
4
5
6
7
8
87654321
87654321
87654321
87654321
87654321
87654321
87654321
87654321
The start bit for this value is 49, as it is the least significant bit of the data value
within the data frame that this parameter refers to.
An example for Accelerator pedal position is shown below.
'Set scan rate
Const PERIOD = 1
'Scan interval number
Const P_UNITS = 2
'Scan interval units (Secs)
'\\\\\\\\\\\\\\\\\\\\\\\\\ CANBUS CONSTANTS //////////////////////
'------------------- Physical Network Parameters ----------------Const TQUANT = 4
Const TSEG1 = 5
Const TSEG2 = 2
')Set SDM-CAN to 250K
')Network speed
')
'---------------------- Data Frame Parameters -------------------'___________________________CANbus Block1_________________________
'Collect and retrieve 16 bit data value
'Data type 2, unsigned integer, least significant byte first
Const CANREP1 = 1
Const ADDRESS1 = 0
Const DATATYPE1 = 2
Const STARTBIT1 = 49
Const NUMBITS1 = 8
Const NUMVALS1 = 1
Dim CANBlk1(CANREP1)
'Repetitions
'SDM address of SDM-CAN
'Collect and retrieve data values
'Start position in data frame
'Number of bits/value
'Number of values
'Dimensioned source
C-3
SDM-CAN CAN-Bus Interface User Guide
'\\\\\\\\\\\\\\\\\\ ALIASES & OTHER VARIABLES //////////////////
Alias CANBlk1(1) = Accel_Pedal
'Assign an alias name to CANBlk2(1)
'\\\\\\\\\\\\\\\\\\\\\\\\\\\ PROGRAM ///////////////////////////
BeginProg
'Program begins here
'MainSequence
Scan(PERIOD,P_UNITS,0,0)
'Scan once every 1 Secs, non-burst
'__________________________ CAN Blocks __________________________
'Retrieve Accelerator pedal position Data from CAN network
CanBus(CANBlk1(),ADDRESS1,TQUANTA,TSEG1,TSEG2,217056000,
DATATYPE1,STARTBIT1,NUMBITS1,NUMVALS1,0.4,0)
Next Scan
'Loop up for the next scan
EndProg
'Program ends here
NOTE
Due to current system constraints the ID parameter must be entered
directly into the CanBus instruction.
C.5 Retrieving J1939 Accelerator Pedal Position Data
using a CR23X/CR10X (Bus Speed 250k Baud)
C.5.1 Encoding the Identifier Field Values
The following example shows how to encode the identifier field values into the
format for the CR23X/CR10X ID parameter.
The identifier field values for the CAN Data Frame are as follows:
Priority
310
Reserved
010
Data Page
010
PDU Format
24010
PDU Specific
310
Source Address
010
These decimal values then need to be converted to binary and encoded into the 29
bit identifier.
C-4
Priority
0112
Reserved
02
Data Page
02
PDU Format
111100002
PDU Specific
000000112
Source Address
000000002
Appendix C. Using SDM-CAN on J1939 Networks
Table C-6 Mapping of J1939 Identifier Field Values into a 29-Bit Identifier
Bit
28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9
8
7
6
5
4
3
2
1
0
SOF P P P R D P P P P P P P P P P P P P P P P S S S S S S S S
3 2 1 1 P F F F F F F F F S S S S S S S S A A A A A A A A
8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1
Value 0 1 1 0 0 1 1 1 1 0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 0 0 0 0 0
This gives a binary value of 01100111100000000001100000000 that can then be
split into three values for use as the ID parameter.
The first value is made up of bits 0..10 which is 011000000002 this is converted to
76810 and used as the first ID parameter.
The second value is made up of bits 11..23 which is 11110000000002 this is
converted to 768010 and used as the second ID parameter.
The third value is made up of bits 24..28 which is 011002 this is converted to 1210
and used as the third ID parameter.
C.5.2 Finding the Start Bit
The byte number of the Accelerator pedal position value is 2
Table C-7 Accelerator Pedal Position Value Byte Number
1
2
3
4
5
6
7
8
87654321
87654321
87654321
87654321
87654321
87654321
87654321
87654321
The start bit for this value is 49, as it is the least significant bit of the data value
within the data frame that this parameter refers to.
An example for Accelerator pedal position is shown below.
;{CR23X}
;
*Table 1 Program
01: 1.0
Execution Interval (seconds)
;Retrieve Accelerator pedal position Data from CAN network
8:
1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
SDM-CAN (P118)
0
SDM Address
4
Time Quanta
5
Tseg1
2
Tseg2
768
ID Bits 0..10 (-- for 11-bit CAN ID)
7680
ID Bits 11..23
12
ID Bits 24..28
2
Rx, unsigned int, LSB 1st
49
Start Bit No.
8
No. of Bits
1
No. of Values
7
Loc [ Throttle
]
C-5
SDM-CAN CAN-Bus Interface User Guide
13: 0.125
Mult
14: 0.0
Offset
*Table 2 Program
02: 0.0000
Execution Interval (seconds)
*Table 3 Subroutines
End Program
C-6
Appendix D. Examples of CAN Data
Frames and Data Encoding and
Decoding
This Appendix gives examples of typical CAN data frames with worked examples of how to
encode or decode such data using the SDM-CAN.
Bits are Transmitted (Txed) or Received (Rxed) starting from the left of the data frame.
Txed/Rxed first
Txed/Rxed last
64bit Data Frame
Bit order within
bytes
87654321
87654321
87654321
87654321
87654321
Byte 1
Byte 2
Byte 3
Byte 4
Byte 5
Byte order
87654321
87654321
Byte 6
87654321
Byte 7
Byte 8
Right Hand Ref
64
57
56
49
48
41
40
33
32
25
24
17
16
9
8
1
Left Hand Ref
1
8
9
16
17
24
25
32
33
40
41
48
49
56
57
64
49
64
57
For the Left Hand Reference, some manufacturers may number the bits in the following order:
Left Hand Ref
8
1
16
9
24
17
32
25
40
33
48
41
56
An additional variation is that sometimes the bit numbering starts from 0 instead of 1.
16bit Data Frame
Bit order within bytes
87654321
Byte order
Byte 1
Right Hand Ref
16
9
Left Hand Ref
1
8
87654321
Byte 2
8
1
9
16
Data encoded/decoded from right to left in all cases.
Examples of values within a data-frame
16bit data frame with a one value 16bit unsigned integer LSByte first
Rxed Bit order within bytes
87654321
Rxed Byte order
87654321
Byte 1
Byte 2
Values
A
Bit order within values
8
1
16
9
Value byte order
LSByte
Start bit (parameter 09:) RH ref
16
9
8
1
Start bit (parameter 09:) LH ref
1
8
9
16
MSByte
This number is
entered into the
P118 DLD
instruction
D-1
SDM-CAN CAN-Bus Interface User Guide
Start bit (parameter 09:) Right Hand reference.
1: SDM-CAN (P118)
1: 0
SDM Address
2: 1
Time-quanta
3: 5
Tseg1
4: 2
Tseg2
5: 1000
ID Bits 0..10
6: 0000
ID Bits 11..23
7: 00
ID Bits 24..28
8: 2
Rx, unsigned int, LSB 1st
9: 9
Start Bit No.
10: 16
No. of Bits
11: 1
No. of Values
12: 1
Loc [ value_A
]
13: 1.0
Mult
14: 0.0
Offset
Start bit (parameter 09:) Left Hand reference.
2: SDM-CAN (P118)
1: 00
SDM Address
2: 1
Time-quanta
3: 5
Tseg1
4: 4
Tseg2
5: 1001
ID Bits 0..10
6: 0000
ID Bits 11..23
7: 00
ID Bits 24..28
8: 2
Rx, unsigned int, LSB 1st
9: 8
-- Start Bit No.
10: 16
No. of Bits
11: 1
No. of Values
12: 1
Loc [ value_A
]
13: 1.0
Mult
14: 0.0
Offset
32bit data frame with two 16bit unsigned integer values LSByte first.
Rxed Bit order within bytes
87654321
87654321
87654321
87654321
Byte 1
Byte 2
Byte 3
Byte 4
Rxed Byte order
D-2
Values
B
A
Bit order within values
8
Value byte order
LSByte
MSByte
LSByte
Start bit (parameter 09:) RH ref
32
25
24
17
16
9
8
1
Start bit (parameter 09:) LH ref
1
8
9
16
17
24
25
32
1
16
9
8
1
16
9
MSByte
Appendix D. Examples of Encoding & Decoding
Start bit (parameter 09:) Right Hand reference.
1: SDM-CAN (P118)
1: 0
SDM Address
2: 1
Time-quanta
3: 5
Tseg1
4: 2
Tseg2
5: 1000
ID Bits 0..10
6: 0000
ID Bits 11..23
7: 00
ID Bits 24..28
8: 2
Rx, unsigned int, LSB 1st
9: 9
Start Bit No.
10: 16
No. of Bits
11: 2
No. of Values
12: 1
Loc [ value_A
]
13: 1.0
Mult
14: 0.0
Offset
Start bit (parameter 09:) Left Hand reference.
2: SDM-CAN (P118)
1: 00
SDM Address
2: 1
Time-quanta
3: 5
Tseg1
4: 4
Tseg2
5: 1001
ID Bits 0..10
6: 0000
ID Bits 11..23
7: 00
ID Bits 24..28
8: 2
Rx, unsigned int, LSB 1st
9: 24
-- Start Bit No.
10: 16
No. of Bits
11: 2
No. of Values
12: 1
Loc [ value_A
]
13: 1.0
Mult
14: 0.0
Offset
24bit data frame with two 12bit unsigned integer values LSByte first
Rxed Bit order within bytes
87654321
87654321
87654321
Byte 1
Byte 2
Byte 3
Rxed Byte order
Values
B
A
Bit order within values
8
Value byte order
LSByte
LSNib
Start bit (parameter 09:) RH ref
24
17
16
13
12
9
8
1
Start bit (parameter 09:) LH ref
1
8
9
12
13
16
17
24
1
4
B
1
A
12
9
MSNib
12
5
MSByte
D-3
SDM-CAN CAN-Bus Interface User Guide
Start bit (parameter 09:) Right Hand reference.
1: SDM-CAN (P118)
1: 0
SDM Address
2: 1
Time-quanta
3: 5
Tseg1
4: 2
Tseg2
5: 1000
ID Bits 0..10
6: 0000
ID Bits 11..23
7: 00
ID Bits 24..28
8: 2
Rx, unsigned int, LSB 1st
9: 13
Start Bit No.
10: 12
No. of Bits
11: 2
No. of Values
12: 1
Loc [ value_A
]
13: 1.0
Mult
14: 0.0
Offset
Start bit (parameter 09:) Left Hand reference.
2: SDM-CAN (P118)
1: 00
SDM Address
2: 1
Time-quanta
3: 5
Tseg1
4: 4
Tseg2
5: 1001
ID Bits 0..10
6: 0000
ID Bits 11..23
7: 00
ID Bits 24..28
8: 2
Rx, unsigned int, LSB 1st
9: 12
-- Start Bit No.
10: 12
No. of Bits
11: 2
No. of Values
12: 1
Loc [ value_A
]
13: 1.0
Mult
14: 0.0
Offset
16bit data frame with one 12bit signed integer value LSByte first
Rxed Bit order within bytes
Rxed Byte order
87654321
87654321
Byte 1
Byte 2
Values
A
Bit order within values
4
Value byte order
LSNib
Start bit (parameter 09:) RH ref
16
13
12
9
8
1
Start bit (parameter 09:) LH ref
1
4
5
8
9
16
1
S
A
12
5
MSByte
S = sign bit which is the MSBit of the value, bit 12.
D-4
Appendix D. Examples of Encoding & Decoding
Start bit (parameter 09:) Right Hand reference.
1: SDM-CAN (P118)
1: 0
SDM Address
2: 1
Time-quanta
3: 5
Tseg1
4: 2
Tseg2
5: 1000
ID Bits 0..10
6: 0000
ID Bits 11..23
7: 00
ID Bits 24..28
8: 4
Rx, signed int, LSB 1st
9: 13
Start Bit No.
10: 12
No. of Bits
11: 1
No. of Values
12: 1
Loc [ value_A
]
13: 1.0
Mult
14: 0.0
Offset
Start bit (parameter 09:) Left Hand reference.
2: SDM-CAN (P118)
1: 00
SDM Address
2: 1
Time-quanta
3: 5
Tseg1
4: 4
Tseg2
5: 1001
ID Bits 0..10
6: 0000
ID Bits 11..23
7: 00
ID Bits 24..28
8: 4
Rx, signed int, LSB 1st
9: 4
-- Start Bit No.
10: 12
No. of Bits
11: 1
No. of Values
12: 1
Loc [ value_A
]
13: 1.0
Mult
14: 0.0
Offset
40bit data frame with one 32bit IEEE floating point value LSByte first
Rxed Bit order within bytes
87654321
87654321
87654321
87654321
Byte 1
Byte 2
Byte 3
Byte 4
Rxed Byte order
Values
A
Bit order within values
8
Value byte order
Mantisa
1
16
9
24
17
87654321
Byte 5
32
25
Exponent
Start bit (parameter 09:) RH ref
40
33
32
25
24
17
16
9
8
1
Start bit (parameter 09:) LH ref
1
8
9
16
17
24
25
32
33
40
D-5
SDM-CAN CAN-Bus Interface User Guide
Start bit (parameter 09:) Right Hand reference.
1: SDM-CAN (P118)
1: 0
SDM Address
2: 1
Time-quanta
3: 5
Tseg1
4: 2
Tseg2
5: 1000
ID Bits 0..10
6: 0000
ID Bits 11..23
7: 00
ID Bits 24..28
8: 6
Rx, real IEEE4, LSB 1st
9: 25
Start Bit No.
10: 32
No. of Bits
11: 1
No. of Values
12: 1
Loc [ value_A
]
13: 1.0
Mult
14: 0.0
Offset
Start bit (parameter 09:) Left Hand reference.
2: SDM-CAN (P118)
1: 00
SDM Address
2: 1
Time-quanta
3: 5
Tseg1
4: 4
Tseg2
5: 1001
ID Bits 0..10
6: 0000
ID Bits 11..23
7: 00
ID Bits 24..28
8: 6
Rx, real IEEE4, LSB 1st
9: 16
-- Start Bit No.
10: 32
No. of Bits
11: 1
No. of Values
12: 1
Loc [ value_A
]
13: 1.0
Mult
14: 0.0
Offset
16bit data frame with one 16bit unsigned integer value MSByte first
Rxed Bit order within bytes
87654321
Rxed Byte order
D-6
87654321
Byte 1
Byte 2
Values
A
Bit order within values
16
Value byte order
MSByte
Start bit (parameter 09:) RH ref
16
9
8
1
Start bit (parameter 09:) LH ref
1
8
9
16
9
8
1
LSByte
Appendix D. Examples of Encoding & Decoding
Start bit (parameter 09:) Right Hand reference.
1: SDM-CAN (P118)
1: 0
SDM Address
2: 1
Time-quanta
3: 5
Tseg1
4: 2
Tseg2
5: 1000
ID Bits 0..10
6: 0000
ID Bits 11..23
7: 00
ID Bits 24..28
8: 1
Rx, unsigned int, MSB 1st
9: 1
Start Bit No.
10: 16
No. of Bits
11: 1
No. of Values
12: 1
Loc [ value_A
]
13: 1.0
Mult
14: 0.0
Offset
Start bit (parameter 09:) Left Hand reference.
2: SDM-CAN (P118)
1: 00
SDM Address
2: 1
Time-quanta
3: 5
Tseg1
4: 4
Tseg2
5: 1001
ID Bits 0..10
6: 0000
ID Bits 11..23
7: 00
ID Bits 24..28
8: 1
Rx, unsigned int, MSB 1st
9: 16
-- Start Bit No.
10: 16
No. of Bits
11: 1
No. of Values
12: 1
Loc [ value_A
]
13: 1.0
Mult
14: 0.0
Offset
32bit data frame with two 16bit signed integer values MSByte first
Rxed Bit order within bytes
87654321
87654321
87654321
87654321
Byte 1
Byte 2
Byte 3
Byte 4
Rxed Byte order
Values
S
B
Bit order within values
16
Value byte order
MSByte
LSByte
MSByte
Start bit (parameter 09:) RH ref
32
25
24
17
16
9
8
1
Start bit (parameter 09:) LH ref
1
8
9
16
17
24
25
32
9
S
8
1
A
16
9
8
1
LSByte
S = sign bit which is the MSBit of the values, bit 16.
D-7
SDM-CAN CAN-Bus Interface User Guide
Start bit (parameter 09:) Right Hand reference.
1: SDM-CAN (P118)
1: 0
SDM Address
2: 1
Time-quanta
3: 5
Tseg1
4: 2
Tseg2
5: 1000
ID Bits 0..10
6: 0000
ID Bits 11..23
7: 00
ID Bits 24..28
8: 3
Rx, signed int, MSB 1st
9: 1
Start Bit No.
10: 16
No. of Bits
11: 2
No. of Values
12: 1
Loc [ value_A
]
13: 1.0
Mult
14: 0.0
Offset
Start bit (parameter 09:) Left Hand reference.
2: SDM-CAN (P118)
1: 00
SDM Address
2: 1
Time-quanta
3: 5
Tseg1
4: 4
Tseg2
5: 1001
ID Bits 0..10
6: 0000
ID Bits 11..23
7: 00
ID Bits 24..28
8: 3
Rx, signed int, MSB 1st
9: 32
-- Start Bit No.
10: 16
No. of Bits
11: 2
No. of Values
12: 1
Loc [ value_A
]
13: 1.0
Mult
14: 0.0
Offset
24bit data frame with two 12bit unsigned integer values MSByte first
Rxed Bit order within bytes
87654321
87654321
87654321
Byte 1
Byte 2
Byte 3
Rxed Byte order
D-8
Values
B
A
Bit order within values
12
Value byte order
MSByte
LSNib
MSNib
Start bit (parameter 09:) RH ref
24
17
16
13
12
9
8
1
Start bit (parameter 09:) LH ref
1
8
9
12
13
16
17
24
5
4
1
12
9
8
1
LSByte
Appendix D. Examples of Encoding & Decoding
Start bit (parameter 09:) Right Hand reference.
1: SDM-CAN (P118)
1: 0
SDM Address
2: 1
Time-quanta
3: 5
Tseg1
4: 2
Tseg2
5: 1000
ID Bits 0..10
6: 0000
ID Bits 11..23
7: 00
ID Bits 24..28
8: 1
Rx, unsigned int, MSB 1st
9: 1
Start Bit No.
10: 12
No. of Bits
11: 2
No. of Values
12: 1
Loc [ value_A
]
13: 1.0
Mult
14: 0.0
Offset
Start bit (parameter 09:) Left Hand reference.
2: SDM-CAN (P118)
1: 00
SDM Address
2: 1
Time-quanta
3: 5
Tseg1
4: 4
Tseg2
5: 1001
ID Bits 0..10
6: 0000
ID Bits 11..23
7: 00
ID Bits 24..28
8: 1
Rx, unsigned int, MSB 1st
9: 24
-- Start Bit No.
10: 12
No. of Bits
11: 2
No. of Values
12: 1
Loc [ value_A
]
13: 1.0
Mult
14: 0.0
Offset
16bit data frame with one 12bit unsigned integer value MSByte first
Rxed Bit order within bytes
Rxed Byte order
Values
A
Bit order within values
12
Value byte order
87654321
87654321
Byte 1
Byte 2
A
9
8
MSNib
1
LSByte
Start bit (parameter 09:) RH ref
16
13
12
9
8
1
Start bit (parameter 09:) LH ref
1
4
5
8
9
16
D-9
SDM-CAN CAN-Bus Interface User Guide
Start bit (parameter 09:) Right Hand reference.
1: SDM-CAN (P118)
1: 0
SDM Address
2: 1
Time-quanta
3: 5
Tseg1
4: 2
Tseg2
5: 1000
ID Bits 0..10
6: 0000
ID Bits 11..23
7: 00
ID Bits 24..28
8: 1
Rx, unsigned int, MSB 1st
9: 1
Start Bit No.
10: 12
No. of Bits
11: 1
No. of Values
12: 1
Loc [ value_A
]
13: 1.0
Mult
14: 0.0
Offset
Start bit (parameter 09:) Left Hand reference.
2: SDM-CAN (P118)
1: 00
SDM Address
2: 1
Time-quanta
3: 5
Tseg1
4: 4
Tseg2
5: 1001
ID Bits 0..10
6: 0000
ID Bits 11..23
7: 00
ID Bits 24..28
8: 1
Rx, unsigned int, MSB 1st
9: 16
-- Start Bit No.
10: 12
No. of Bits
11: 1
No. of Values
12: 1
Loc [ value_A
]
13: 1.0
Mult
14: 0.0
Offset
40bit data frame with one 32bit IEEE floating point value MSByte first
Rxed Bit order within bytes
87654321
87654321
87654321
87654321
87654321
Byte 1
Byte 2
Byte 3
Byte 4
Byte 5
Rxed Byte order
D-10
Values
A
Bit order within values
32
Value byte order
Exponent
Mantisa
25
24
17
16
9
8
1
Start bit (parameter 09:) RH ref
40
33
32
25
24
17
16
9
8
1
Start bit (parameter 09:) LH ref
1
8
9
16
17
24
25
32
33
40
Appendix D. Examples of Encoding & Decoding
Start bit (parameter 09:) Right Hand reference.
1: SDM-CAN (P118)
1: 0
SDM Address
2: 1
Time-quanta
3: 5
Tseg1
4: 2
Tseg2
5: 1000
ID Bits 0..10
6: 0000
ID Bits 11..23
7: 00
ID Bits 24..28
8: 5
Rx, real IEEE4, MSB 1st
9: 1
Start Bit No.
10: 32
No. of Bits
11: 1
No. of Values
12: 1
Loc [ value_A
]
13: 1.0
Mult
14: 0.0
Offset
Start bit (parameter 09:) Left Hand reference.
2: SDM-CAN (P118)
1: 00
SDM Address
2: 1
Time-quanta
3: 5
Tseg1
4: 4
Tseg2
5: 1001
ID Bits 0..10
6: 0000
ID Bits 11..23
7: 00
ID Bits 24..28
8: 5
Rx, real IEEE4, MSB 1st
9: 40
-- Start Bit No.
10: 32
No. of Bits
11: 1
No. of Values
12: 1
Loc [ value_A
]
13: 1.0
Mult
14: 0.0
Offset
D-11
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