Application Note Document CANopen Encoder Gateway

Application Note Document CANopen Encoder Gateway
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CANopen Encoder Gateway
Application and Installation information
1.
2.
3.
4.
INTRODUCTION
1.1
1.2
CANopen communication model
Profile overview
3
3
1.3
References
4
FUNCTIONAL OVERVIEW
6.
7.
8.
4
2.1
2.2
Default Identifiers
Boot-up message
4
5
2.3
Encoder functionality
5
SCALING FUNCTION
6
3.1 Overview
3.2 Scaling formulas
3.2.1
Measuring range
6
7
7
PRESET VALUE
8
4.1
4.2
5.
3
Overview
Preset formula
8
9
INSTALLATION
9
5.1
Power supply cable
5.2
5.3
5.4
5.5
Bus cable
Encoder cable
Address setting
Baudrate setting
10
10
10
11
5.6
5.7
5.8
EDS and DCF files
Parameter settings
Incremental signal output (optional)
11
12
12
MANUFACTURER SPECIFIC FUNCTIONS
9
13
6.1
6.2
Object 5000h - Transmission rate
Object 5001h - Node number
13
14
6.3
Object 5500h – Gateway Serial number
15
ENCODER TYPES
16
7.1
7.2
Singleturn Encoders 13 bit
Multiturn Encoders 25 bit
16
16
7.3
7.4
Angle Encoders
Linear Encoders
16
16
ENCODER SETUP EXAMPLE
APPENDIX A, HISTORY
17
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1.
Introduction
This document contains application and installation information on the Leine &
Linde CANopen Encoder Gateway based on the CiA CANopen Encoder Profile
DS 406. The Encoder Gateway support all functions of the profile.
The gateway is the interface between the CAN bus and the encoder. The
communication between the gateway and the encoder is handled through a fast
Bidirectional Synchronous-Serial Interface called Endat. In the EnDat encoder
advanced diagnostics are integrated together with the position sensing parts to
make it possible to check the correctness of the position value very thoroughly.
1.1
CANopen communication model
The CANopen communication profile is based on the CAN Application Layer
(CAL) specification from the CiA (CAN in Automation). CANopen comprises a
concept to configure and communicate real-time data using both synchronous
and asynchronous messages. Four types of message (objects) are distinguished:
1. Administrative messages (Layer Management, Network Management and
Identifier Distribution Messages)
2. Service Data Messages (SDO)
3. Process Data Messages (PDO)
4. Pre-defined Messages (Synchronisation-, Time-stamp-, Emergency
Messages)
For further information please see the CANopen specification.
1.2
Profile overview
The Encoder Profile defines the functionality of encoders connected to
CANopen. The operating functions are divided in two device classes:
- Class 1, the Mandatory class with a basic range of functions that all Encoders
must support. The class 1 encoder can optionally support selected class 2
functions, these functions must however be implemented according to the profile.
- Class 2, where the Encoder must support all class 1 functions and all functions
defined in class 2. The full class 2 functionality includes:
• Absolute position value transfer using either polled, cyclic or sync mode.
• Change of code sequence
• Preset value settings
• Scaling of the encoder resolution
Advanced diagnostics including:
• Encoder identification
• Operating status
• Operating time
• Alarms and warnings
All programming and diagnostic parameters are accessible through SDOs. The
output position value from the encoder is presented in binary format.
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1.3
2.
References
http://www.can-cia.de
CAN Application Layer, DS 201 …207
CAL Based Communication Profile, DS 301
Device Profile for Encoders, DS 406
CAN Specification Version 2.0 A
82527 Architectural Overview
CiA
CiA
CiA
Robert Bosch Gmbh
Intel
Functional overview
2.1
Default Identifiers
In order to reduce configuration effort a default identifier allocation scheme is
defined for CANopen devices. This ID-allocation scheme consists of a functional
part, which determines the object priority and a module-ID-part, which is equal
to the node number (1 to 127). Broadcasting of non-confirmed services (NMT,
SYNC and node guarding) is indicated by a module-ID of zero.
In CANopen the 11 bit identifier is build as follows:
Bit-Nr.
10
9
8
7
Function Code
6
5
4
3
2
1
0
Node Number
The following broadcast objects with default identifiers are available in the
encoder:
Object
NMT
SYNC
Function Code
(binary)
0000
0001
Resulting Identifier Priority group
(COB-ID)
0
0
128
0
The following Peer-to-Peer objects with default identifiers are available in the
encoder:
Object
Function Code
(binary)
EMERGENCY 0001
PDO1 (tx)
0011
PDO2 (tx)
0101
SDO (tx)
1011
SDO (rx)
1100
Nodeguard
1110
Resulting Identifier
(COB-ID)
129 – 255
385 – 511
641 – 767
1409 – 1535
1537 – 1663
1793 – 1919
Priority group
0, 1
1, 2
2, 3
6
6, 7
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2.2
Boot-up message
The encoder sends a Boot-up message after power-on and initialisation. This
message uses the default emergency identifier and has no data bytes. With this
message the user can retrieve the sending node directly from the used identifier
(COB-ID) as it is a function of the node number, see 2.1.
2.3
Encoder functionality
The figure below gives an overview of the Encoder functions.
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3.
Scaling function
3.1
Overview
With the scaling function the Encoder internal numerical value is converted in
software to change the physical resolution of the Encoder.
The parameters ”Measuring units per revolution” and ”Total measuring range in
measuring units” are the scaling parameters set to operation with the scaling
function control bit.
NOTE! When scaling a Multiturn encoder the parameter “Measuring units per
revolution” must be sent before the parameter “Total measuring range in
measuring units”.
The data type for both scaling parameters is unsigned 32 with a value range
from 1 to 2 32 limited by the encoder resolution. For a 25 bit encoder with a
singleturn resolution of 13 bits the permissible value for the ”Measuring units
per revolution” is between 1 and 213 (8192) and for the ”Total measuring range
in measuring units” the permissible value is between 1 and 225 (33 554 432).
The scaling parameters are securely stored in case of voltage breakdown and
reloaded at each start-up.
Scaling parameter format:
Byte
3
2
1
0
Bit
31 - 24
23 - 16
15 - 8
7 - 0
Data
231 - 224
223 - 216
215 - 28
27 - 20
Object 6001h - Measuring units per revolution
Byte
3
2
1
0
Bit
31 - 24
23 - 16
15 - 8
7 - 0
Data
231 - 224
223 - 216
215 - 28
27 - 20
Object 6002h - Total measuring range in measuring units
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3.2
Scaling formulas
The scaling function used in the CAN encoder gateway is limited to a singleturn
resolution within one step. After downloading new scaling parameters the
preset function should be used to set the encoder starting point to the required
starting point.
NOTE! Changing the scaling function parameters should only be used at encoder
standstill.
In the following formulas a 25 bit multiturn encoder with a singleturn resolution
of 13 bits is used as an example.
Formula for the multiturn scaling function:
A = measuring_units_per_revolution * singleturn_position / 8192
output_position = (revolution_number * measuring_units_per_revolution) + A
where:
singleturn_position =
revolution_number =
3.2.1
the Absolute position value of the encoder singleturn
disk
the Absolute revolution number of the encoder
multiturn disks
Measuring range
The measuring range is set by the parameter ”Total measuring range in
measuring units”. The encoder has two different operating modes depending on
the specified measuring range. When the encoder recieves new scaling
parameters it checks the values for binary scaling and chooses operating mode
A if binary scaling detected, see explanation below.
A. Cyclic operation (Binary scaling)
Used when operating with 2x number of turns (2, 4, 8, 16, 32, 64, 128, 256, 512,
1024, 2048 and 4096 number of turns).
If the desired measuring range is equal to the specified singleturn resolution * 2x
(where x <= 12) the encoder operates in endless cyclic operation (0 max - 0 - max ...). For example: If the position value increases above the
maximum value (measuring range-1) by rotating the encoder beyond the
maximum value the encoder continues from 0.
Example of a cyclic scaling:
Measuring units per revolution
= 1000
Measuring range
= 32000 (2 5 = 32 number of turns)
B. Non cyclic operation
If the measuring range is used to limit the encoder value range to a value not
equal to the specified singleturn resolution * 2x the output position value is
limited within the operating range. If the position value increases or decreases
outside the measuring range by rotating the encoder beyond the maximum value
(measuring range-1) or below 0 the encoder outputs the total measuring range
value, see figure below.
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Example of a non cyclic scaling:
Measuring units per revolution:
Total measuring range:
4.
100
5000 steps (50 turns)
Preset value
4.1
Overview
The preset function supports adaptation of the encoder zero point to the
mechanical zero point of the system. The preset function sets the actual position
of the encoder to the preset value. The preset function is used after the
scaling function which means that the preset value is given in the current
measuring units.
A preset is handled by the encoder in the following way:
The encoder reads the current position value and calculates an offset value from
the preset value and the read position value. The position value is shifted with the
calculated offset value. The offset value can be read with the diagnostic function
(Object 6509h) and is securely stored in case of voltage breakdown and reloaded
at each start-up.
NOTE! The preset function should only be used at encoder standstill.
Preset value format:
Byte
3
2
1
0
Bit
31 - 24
23 - 16
15 - 8
7 - 0
Data
231 - 224
223 - 216
215 - 28
27 - 20
Object 6003h - Preset Value
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4.2
Preset formula
An offset_value is calculated when the encoder receives the preset_value, see
setup calculation below. The offset_value is then used during runtime to shift
the current position to get the required output position, see runtime calculation
below.
NOTE! In the formulas below the current_position is the Absolute position of
the encoder disk after the scaling function. The calculations are made with
signed values.
Setup calculation:
offset_value = preset_value - current_position
NOTE! A previously set offset_value is not included in the current position.
Runtime calculation:
output_position = current_position + offset_value
5.
Installation
This section handles the installation issues of the Encoder Gateway.
5.1
Power supply cable
The gateway should be supplied with 9-30VDC through the integrated screw
terminal block. A shielded power cable must be used.
Installation:
1. Remove the cover of the gateway box.
2. Strip the cable ends to the appropriate length, leave app. 15mm of the shield
for connection to the cable gland.
3. Insert the power cable through the cable gland.
4. Connect the cables to the +E and 0V screw terminal block. Tighten the
terminal screws.
5. Tighten the cable gland and make sure the shield is connected to the gland.
6. Close the cover of the gateway box.
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5.2
the same
Bus cable
The Encoder gateway includes an isolated bus interface separating the power
supply and the CAN transceiver supply. The transceiver ground is available at
the screw terminals marked CAN_GND.
A shielded twisted pair wire with specifications according to the CAN standard
must be used.
The gateway includes a build in T-coupling with a screw terminal block for
CAN_H, CAN_L and CAN_GND. When the gateway is used as the first or last
station on the BUS, the cable can be connected on either IN or OUT terminal
with the terminating resistor switch (TERM.R.) set to ON.
Installation:
1. Remove the cover of the gateway box.
2. Strip the cable ends to the appropriate length, leave app. 15mm of the shield
for connection to the cable gland.
3. Insert the bus cable through the cable gland.
4. Connect the cable conductors to the screw terminal block marked BUS (IN or
OUT). Make
sure that the same conductor is always connected to
terminal (e.g. green conductor always connected to CAN_H, red conductor
always connected to CAN_L). Tighten the terminal screws.
5. Set the terminating resistor switch (TERM.R.) to ON if this is the first or
last station on the bus.
6. Tighten the cable gland and make sure the shield is connected to the gland.
7. Close the cover of the gateway box.
5.3
Encoder cable
Installation:
1. Make sure the power supply to the gateway is switched off.
2. Connect the male cable-connector to the gateway.
3. Connect the female cable-connector to the encoder.
4. Switch on the gateway power supply.
5.4
Address setting
The physical address (node number) of the gateway must be set between 1 - 127
with the address switch inside the gateway. The address is set in binary code (the
value for each switch position is marked beside the switch). The gateway reads
the address switch only at power-up.
The gateway also support setting the physical address from the CAN master
through a separate object, for information see the manufacturer specific functions
below.
NOTE! The selected address (node number) affects the default identifier
allocation, see section 2 for further information.
Setting of the address:
1. Make sure the power supply to the gateway is switched off.
2. Set the address with the dipswitches.
3. Switch on the gateway power supply.
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5.5
Baudrate setting
The transmission rate of the gateway must be set with the Baudrate switch inside
the gateway. The value is set with three dip-switches (Switch 8,9,10 on SW1) as
a binary code representing the selected transmission rate. The gateway reads the
Baudrate switch only at power-up.
The gateway also support setting the transmission rate from the CAN master
through a separate object, for further information see the manufacturer specific
functions below.
Setting of the transmission rate:
1. Make sure the power supply to the gateway is switched off.
2. Set the transmission rate code with the dipswitches, see table below.
3. Switch on the gateway power supply.
Dip-switch value
0
1
2
3
4
5
6
7
5.6
Transmission rate
10 kBit/s
20 kBit/s
50 kBit/s
125 kBit/s
250 kBit/s
500 kBit/s
800 kBit/s
1.000 kBit/s
Switch 8
OFF
ON
OFF
ON
OFF
ON
OFF
ON
Switch 9
OFF
OFF
ON
ON
OFF
OFF
ON
ON
Switch 10
OFF
OFF
OFF
OFF
ON
ON
ON
ON
EDS and DCF files
An EDS-file (Electronic Data Sheet) is delivered together with the CANopen
Encoder Gateway. The EDS file describes:
• The communication functionality and objects as defined in the CANopen
communication profile DS-301.
• The device specific objects as defined in the Encoder Profile DS-406.
• Manufacturer specific objects.
The EDS file serves as a template for different configurations of one device type.
A DCF-file (Device Configuration File) is generated from the EDS-file describing
a specific configuration of the device including object values, selected baudrate
and module-Id.
CANopen configuration tools are available to support CANopen network
configuration and device configuration via the CAN bus. The information about
the device is obtained from the EDS-file.
NOTE! The EDS Installation procedure depends on your configuration tool,
please consult your tool supplier if you run into problems.
Installation example for PRO-CANopen:
1. Copy the EDS file into the EDS directory created by PRO-CANopen.
2. Select the type of device to be configured, a list of EDS-files is displayed,
select the required EDS-file.
3. An empty DCF file is created and the configuration of the device can start.
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5.7
Parameter settings
The parameters are usually set from the configuration tool when the device is in
the Pre-Operational state using the objects obtained from the EDS-file. The
parameters can also be changed during runtime (Operational state), please be
careful as the position data is directly effected by some parameters and will
change directly following such parameter message. Therefore changing the
scaling function parameters and the code sequence should only be used at
encoder standstill.
NOTE! The parameterisation procedure depends on your configuration tool,
please consult your tool supplier if you run into problems.
5.8
Incremental signal output (optional)
The absolute encoder connected to the CAN Gateway provides two incremental
sinusoidal outputs A and B. The signals is distributed through a connector on the
Gateway. The signal amplitude is 1Vpp with terminating resistor Z0 = 120 ohm.
See enclosed information for recommended input circuitry.
Chassis connector: EUCHNER SD 4 K
Cable connector: EUCHNER BS 4 K (Leine & Linde Art.nr: 002 01 029)
Pin No.
1
2
3
4
Signal
Colour
A+
AB+
B-
Green/black
Yellow/black
Blue/black
Red/black
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6.
Manufacturer specific functions
6.1
Object 5000h - Transmission rate
Eight transmission rates are supported by the encoders. The selection of the
transmission rate can be done either by Object 5000h or by hardware. By writing
the value FFh to Object 5000h the encoder gets the transmission rate by
hardware. Changing to Software mode is done by writing the desired
transmission rate code to Object 5000h. The transmission rate will be valid after
next power-up (next initialisation sequence).
OBJECT DESCRIPTION
INDEX
5000 H
Name
Transmission rate
Object Code
VAR
Data Type
Unsigned 8
VALUE DESCRIPTION
Object Class
Manufacturer specific
Access
Rw
PDO Mapping No
Value Range
Unsigned8
Mandatory
No
Range
Default Value
FFh = Hardware settings
STRUCTURE OF PARAMETER
Value
Function
0
10 kBit/s
1
20 kBit/s
2
50 kBit/s
3
125 kBit/s
4
250 kBit/s
5
500 kBit/s
6
800 kBit/s
7
1.000 kBit/s
FFh
Hardware settings
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6.2
Object 5001h - Node number
The selection of the node number can be done either with Object 5001h or by
hardware (e.g.: dip-switches, pins or wires). By setting the value FFh the encoder
gets the node number by hardware. Changing to Software mode is done by
writing the desired node number to Object 5001h. The node number can be set in
the range 1 – 127.
The node number will be valid after next power-up (initialisation sequence).
OBJECT DESCRIPTION
INDEX
5001 H
Name
Node number
Object Code
VAR
Data Type
Unsigned 8
VALUE DESCRIPTION
Object Class
Manufacturer specific
Access
Rw
PDO Mapping No
Value Range
1 – 127, FFh
Mandatory
No
Range
Default Value
FFh = Hardware settings
STRUCTURE OF PARAMETER
Bit
Function
0
Node number
1
Node number
2
Node number
3
Node number
4
Node number
5
Node number
6
Node number
7
Hardware switching
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6.3
Object 5500h – Gateway Serial number
Object 5500h contains the CANopen Encoder Gateway serial number. It is given
as an unsigned32 binary value. If the gateway serial number is not used the value
is set to maximum value FF FF FF FF h.
OBJECT DESCRIPTION
INDEX
5500 H
Name
Gateway Serial number
Object Code
VAR
Data Type
Unsigned32
VALUE DESCRIPTION
Object Class
Manufacturer specific
Access
R
PDO Mapping No
Value Range
Unsigned32
Mandatory
No
Range
Default Value
No
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7.
Encoder types
A number of different EnDat encoders can be connected to the CANopen
gateway. This section of the document gives you information on the supported
functionality.
7.1
Singleturn Encoders 13 bit
The 13 bit singleturn encoder supports the full class2 functionality.
The Scaling function accepts all values between 2 and 8192 measuring units per
revolution. The total measuring range is equal to the scaled singleturn resolution.
7.2
Multiturn Encoders 25 bit
The 25 bit Multiturn encoder supports the full class2 functionality.
The Scaling function parameter ”measuring units per revolution” accepts all
values between 2 and 8192. The encoder has two different operating modes
(Cyclic or Non-cyclic) depending on the value of the parameter “total measuring
range in measuring units”, please check the section Scaling formulas above for
further information.
7.3
Angle Encoders
EnDat singleturn Angle encoders with a resolution of 20 and 23 bits is currently
supported. The Angle encoders support the full class2 functionality with the
scaling function limited to binary scaling. This means that the parameter
“measuring units per revolution” accepts only values with is equal to 2x where x
is a value from one to 20 (for a 20 bit encoder). Scaling a 20 bit encoder to 18 bit
gives the parameter “measuring units per revolution” the value 218 = 262144.
7.4
Linear Encoders
EnDat Linear encoders is supported with the preset function but currently no
other class2 parameter or the change of code sequence. However access to all
diagnostic objects as the operating time monitor, alarms, warnings and the
encoder serial number is supported. For Linear encoders the Object 6501h
indicates the measuring step in nm that is output by the encoder.
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8.
Encoder setup example
This example shows a simple setup of the Encoder Gateway for cyclic
transmission of the Position value. Read section 2 of this Application note before
proceeding.
1. Set the physical address (Node Number) of the Encoder Gateway by Dipswitches, see section 5.2 for further information.
2. Set the baudrate of your Encoder Gateway by Dip-switches, see section 5.5
for further information.
3. Power up the Encoder Gateway.
4. The Gateway will send a Boot-up message on the default emergency
identifier (ID = 128 + encoder address), the message has no data bytes.
5. The Gateway is now ready for configuration through the SDO message. To
set a cyclic transmission of the position value with 10ms repetition rate we
need to send an SDO request message (ID = 1536 + Gateway address) to the
cyclic timer object (Object 6200h) with the data below. The Gateway will
confirm with the SDO response message (ID = 1408 + Gateway address).
Byte 0
0x22
Byte 1
0x00
Byte 2
0x62
Byte 3
0x00
Byte 4
0x0A
Byte 5
0x00
Byte 6
0x00
Byte 7
0x00
6. To get the Gateway in operation we need to send an NMT “start remote
node” message, ID = 0, two data bytes with the following contents:
Byte 0
0x01
Byte 1
The Gateway address (Node Number)
7. The Gateway has now entered the operational state and the position message
(ID = 384 + Gateway address) is transferred with a 10ms repetition rate. If an
error occur the Gateway will send an emergency message (ID = 128 +
Gateway address).
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Appendix A, History
Revision
Date
Changes
Rev. 1.0
98-02-24
First release
Rev. 1.1
98-03-17
1. Default identifer allocation scheme included
2. Boot-up message included
Rev. 1.2
98-05-25
EnDat Linear encoders is supported with the preset function.
Rev. 1.3
99-03-19
Encoder setup example included.
18
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