GPS6160HR 12 Channel GPS Receiver Module User`s Manual

GPS6160HR
12 Channel GPS Receiver Module
User’s Manual
Hardware revision 1.1
User’s Manual
GPS6160HR
12 Channel GPS Receiver Module
User’s Manual
REAL TIME DEVICES FINLAND OY
LEPOLANTIE 14
FIN-00660 HELSINKI
FINLAND
Phone: (+358) 9 346 4538
FAX: (+358) 9 346 4539
EMail
sales@rtdfinland.fi
techsupport@rtdfinland.fi
Websites
http://www.rtdfinland.fi/
http://www.rtdusa.com/
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WARNING
LIFE SUPPORT APPLICATIONS
This product is not designed for use in life support appliances, devices or systems
where malfunctioning of these products can reasonably be expected to result in
personal injury. RTD customers using or selling this product for use in these
applications do so at their own risk and fully agree to indemnify RTD for any
damages resulting from such improper use or sale.
Revision History
02/05/2002
HW Release 1.1, Preliminary version, released
Notice: We have attempted to verify all information in this manual as of
the publication date. Information in this manual may change without prior
notice from RTD Finland Oy.
Published by:
Real Time Devices Finland Oy
Lepolantie 14
FIN-00660 Helsinki
Finland
Copyright 2002 Real Time Devices Finland Oy
All rights reserved
Printed in Finland
PC/XT, PC/AT are registered trademarks of IBM Corporation.
PC/104 is a registered trademark of the PC/104 Consortium.
The Real Time Devices Logo is a registered trademark of Real Time Devices.
utilityModule is a trademark of Real Time Devices.
All other trademarks appearing in this document are the property of their respective owners.
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Table of Contents
List of illustrations and tables ................................ 5
Chapter 1 Introduction ............................................ 6
Features .................................................................................................. 6
GPS receiver ........................................................................................... 6
16C550 compatible UARTs..................................................................... 6
I/O interfaces........................................................................................... 7
Mechanical description............................................................................ 7
Connector description ............................................................................. 7
What comes with your board?................................................................. 7
Using this manual.................................................................................... 8
When you need help ............................................................................... 8
Chapter 2 Board settings ........................................ 9
Factory configured jumper settings ....................................................... 10
Base address jumpers........................................................................... 11
Host interrupts....................................................................................... 13
Antenna Bias ......................................................................................... 14
Chapter 3 Board installation ................................. 15
Board installation................................................................................... 15
General purpose digital I/O connector .................................................. 16
Chapter 4 Hardware description ........................... 18
GPS receiver ......................................................................................... 19
GPS antenna considerations................................................................. 19
UART serial port circuitry ...................................................................... 20
Digital I/O .............................................................................................. 21
Status LEDs .......................................................................................... 21
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Chapter 5 Board operation and programming..... 22
Defining the memory map .................................................................... 22
GPS BASE+400h Digital I/O ................................................................. 23
GPS BASE+401h status register........................................................... 23
Interrupts ............................................................................................... 23
Chapter 6 GPS6160HR Specifications.................. 30
Chapter 7 Return policy and warranty.................. 31
List of illustrations and tables
Fig. 2-1 GPS6160HR Board layout showing jumper locations
Fig. 2-2 Base address jumpers illustrating address 2E8h
Fig. 2-3 Interrupt jumpers from left to right: IRQ 2,5,6,7,10,11,12,15 and G
Fig. 2-4 Antenna bias selection jumper
Fig. 3-1 GPS6160HR integrated in a RTD PC/104 cpuModule stack
together with a HPWR104HR and a CMM series cpuModule
Fig. 3-2 Digital I/O connector layout of the GPS6160HR
Fig. 4-1 Block diagram of the GPS6160HR
Fig. 4-2 GPS antenna bias voltage
Fig. 4-3 GPS Status LEDs
Table 2-1 Factory configured jumper settings
Table 2-2 Base address jumper settings GPS6160HR
Table 3-1 Pin outs of the GPS6160HR digital I/O interface connector
Table 5-1 General I/O map of the GPS6160HR GPS UART
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Chapter 1 - INTRODUCTION
This user’s manual describes the operation of the RTD GPS6160HR integrated
low power fast fix GPS module designed for mobile, marine, and automotive
applications.
Features
Some of the key features of the GPS6160HR include:
•
•
•
•
•
•
•
•
•
•
•
12-channel low power Fastrax iTrax02 GPS receiver
NMEA and binary protocols
+3,3V and +5V active GPS antenna support
16C550 UART interface to host computer
Supports COM1,COM2,COM3,COM4 or COMx
Available IRQ’s 2,5,6,7,10,11,12,14,15
Status LED’s indicating GPS activity and status
16 TTL I/O’s 8 outputs 8 inputs
+5V only operation, 1.3W typical
Wide operating temperature range –40 to + 85C guaranteed
Fully PC/104 compliant, IDAN versions available
The following paragraphs briefly describe the major features of the
GPS6160HR. A more detailed discussion is included in Chapter 4 (Hardware
description) The boards installation is described in Chapter 2 (Board
Installation).
GPS receiver
Integrated on your GPS6160HR is a fast fix 12-channel low power iTrax02
GPS receiver from Fastrax. This new receiver will work reliably in a
variety of installations. The receiver will work with either 3,3V or 5,0V
active or with passive antennas. The power consumption of the GPS
receiver is 125mW fully operational. A fast 1 to 4Hz updating rate is
achieved using the binary iTalk protocol. Two output formats are
available: the NMEA-0183 ASCII protocol or the iTalk proprietary binary
protocol. Swiching between these protocols is controlled with one bit in
the internal board registers.
16C550 compatible UART
Communication to the GPS6160HR board is performed through a
standard 16C550 compatible UART. This onboard serial port leaves other
system serial ports free for the user. All operating systems will recognize
and support this standard UART, and therefore no special communication
drivers are needed to receive data from your GPS6160HR board. The
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address and interrupt of your serial channels can be individually set with
the onboard jumper fields.
I/O interfaces
The GPS6160HR can be controlled and monitored from the software
through two dedicated I/O registers. A special I/O connector is available
for the user to connect to the general-purpose TTL level digital I/O.
Mechanical description
The GPS6160HR is designed on a PC/104 form factor. An easy
mechanical interface to both PC/104 and RTD IDAN systems can be
achieved. Stack your GPS6160HR directly on a PC/104 compatible CPU
module using the onboard mounting holes and standoffs.
Connector description
The GPS antenna interface uses an OSX type miniature coaxial
connector. Connect your antenna directly to the GPS6160HR antenna
connectors, or use a short cable inside your enclosure to connect to a
feed through connector to allow connection of the antennas to the wall of
your enclosure. All I/O connections are made using header type terminals.
What comes with your board
Your GPS6160HR package contains the following items:
•
•
GPS6160HR board
User's manual
Note: Device drivers and example software available on our website
If any item is missing or damaged, please send an EMAIL to Real Time
Devices Finland sales service department at Internet address:
<sales@rtdfinland.fi>.
Note that RTD Finland also can offer a GPS6160HR starter kit that will
include an active antenna with ready cables for direct evaluation and
testing of this module. The part number for this starter kit is SKGPS6160HR.
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Using this manual
This manual is intended to help you install your new GPS6160HR module
and get it working quickly, while also providing enough detail about the
board and it's functions so that you can enjoy maximum use of it's features
even in the most demanding applications.
When you need help
This manual and all the example programs will provide you with enough
information to fully utilize all the features on this board. If you have any
problems installing or using this board, contact our Technical support
department at <techsupport@rtdfinland.fi>. When sending us an Email
request please include the following information: Your company's name
and address, your name, your telephone number, and a brief description
of the problem.
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Chapter 2 -
BOARD SETTINGS
The GPS6160HR board has jumper settings, which can be changed to
suit your application and host computer configuration. The factory settings
are listed and shown in the diagram at the beginning of this chapter. Make
sure you completely study and understand this chapter before making
changes to these settings.
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Factory-Configured Jumper Settings
Table 2-1 below illustrates the factory jumper setting for the GPS6160HR.
Figure 2-1 shows the board layout of the GPS6160HR and the locations
of the jumpers. The following paragraphs explain how to change the
factory jumper settings to suit your specific application.
Table 2-1 Factory configured jumper settings (Please see figure 2-1 below
for more detailed locations)
JUMPER NAME
BASE
IRQ
DESCRIPTION
Base Addresses
Host interrupts
NUMBER OF JUMPERS
6
11+1
FACTORY SETTING
2E8 / 6E8
5, G – jumper closed
Fig. 2-1 GPS6160HR Board layout showing jumper locations
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Base address jumpers (Factory setting: 2E8h / 6E8h)
The GPS6160HR is I/O mapped into the memory space of your host
XT/AT. The board occupies a memory window of 8 bytes starting from the
base address for UART communication and 4 consecutive bytes starting
from BASE+400h for the board control and status registers. As an
example if your base address is set to be 2E8h for the serial port, the
onboard control registers will start from 6E8h.
The most common cause of failure when you are first setting up your
module is address contention: some of your computers I/O space is
already occupied by other devices and memory resident programs. When
the GPS6160HR attempts to use it's own reserved memory addresses
(which are being already used by another peripheral device) erratic
performance can occur and the data read from the board may be
corrupted.
To avoid this problem make sure you set up the base address by using
the six jumpers on the right side of the board, this allows you to choose
from a number of different addresses in your host computer’s I/O map.
Should the factory-installed settings be incompatible to your system
configuration, you may change this setting to another using the options
illustrated in Table 2-2 (overleaf). The table shows the jumper settings
and their corresponding values in hexadecimal form. Ensure that you
verify the correct location of the base address jumpers. When the jumper
is removed it corresponds to a logical "0", connecting the jumper to a "1".
When you set the base address of the module, record the setting inside
the back cover of this manual.
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GPS6160HR Base address configuration
BASE
200
208
210
218
220
228
230
238
240
248
250
258
260
268
270
278
280
288
290
298
2A0
2A8
2B0
2B8
2C0
2C8
2D0
2D8
2E0
2E8
2F0
2F8
A8 A7 A6 A5 A4
0 0 0 0 0
0 0 0 0 0
0 0 0 0 1
0 0 0 0 1
0 0 0 1 0
0 0 0 1 0
0 0 0 1 1
0 0 0 1 1
0 0 1 0 0
0 0 1 0 0
0 0 1 0 1
0 0 1 0 1
0 0 1 1 0
0 0 1 1 0
0 0 1 1 1
0 0 1 1 1
0 1 0 0 0
0 1 0 0 0
0 1 0 0 1
0 1 0 0 1
0 1 0 1 0
0 1 0 1 0
0 1 0 1 1
0 1 0 1 1
0 1 1 0 0
0 1 1 0 0
0 1 1 0 1
0 1 1 0 1
0 1 1 1 0
0 1 1 1 0
0 1 1 1 1
0 1 1 1 1
0 = JUMPER OFF
A3
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
BASE
300
308
310
318
320
328
330
338
340
348
350
358
360
368
370
378
380
388
390
398
3A0
3A8
3B0
3B8
3C0
3C8
3D0
3D8
3E0
3E8
3F0
3F8
A8 A7 A6 A5 A4
1 0 0 0 0
1 0 0 0 0
1 0 0 0 1
1 0 0 0 1
1 0 0 1 0
1 0 0 1 0
1 0 0 1 1
1 0 0 1 1
1 0 1 0 0
1 0 1 0 0
1 0 1 0 1
1 0 1 0 1
1 0 1 1 0
1 0 1 1 0
1 0 1 1 1
1 0 1 1 1
1 1 0 0 0
1 1 0 0 0
1 1 0 0 1
1 1 0 0 1
1 1 0 1 0
1 1 0 1 0
1 1 0 1 1
1 1 0 1 1
1 1 1 0 0
1 1 1 0 0
1 1 1 0 1
1 1 1 0 1
1 1 1 1 0
1 1 1 1 0
1 1 1 1 1
1 1 1 1 1
A3
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
1 = JUMPER CLOSED
Table 2-2 Base address jumper settings for the GPS6160HR, the default
jumper settings are highlighted.
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Fig. 2-2 Base address jumpers illustrating address 2E8, A8 is to the
bottom, A3 is located to the top of the jumper block
Host interrupts
(Factory setting: IRQ5, G closed)
The header connector, shown in Figure 2-3 below, lets you connect the
onboard control logic interrupt outputs to one of the interrupt channels
available on the host computer XT/AT bus.
Fig. 2-3 Interrupt jumpers from left to right IRQ2,5,6,7,10,11,12,14,15 and G
Note: The GPS6160HR hardware supports interrupt sharing! Jumper G must be
closed on one module per used interrupt. For example if two boards share
interrupt number 7 only one board may have the G jumper closed. The G
jumper connects a 1KOhm resistor to ground while the shared interrupts
are 3-stated pulling the line to an inactive level.
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Antenna Bias
(Factory setting: +5V)
The three terminal jumper header connector, shown in Figure 2-4 below,
lets you connect either +5V or +3,3V to the GPS antenna. This bias
voltage is fused with an 80mA quick blow fuse.
Fig. 2-4 Antenna bias voltage selection jumper
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Chapter 3
BOARD INSTALLATION
The GPS6160HR GPS module is designed to directly mount on top or
under your RTD PC/104 cpuModule stack. This chapter tells you step-bystep how to install your GPS6160HR into your system.
Board installation
Keep your board in its antistatic bag until you are ready to install it to your
system! When removing it from the bag, hold the board at the edges and
do not touch the components or connectors. Please handle the board in
an antistatic environment and use a grounded workbench for testing and
handling of your hardware. Before installing the board in your computer,
check the power cabling. Failure to do so may cause the power supply
unit to malfunction or even cause permanent damage.
General installation guidelines:
•
•
•
•
•
•
•
GPS6160HR
Touch the grounded metal housing of your computer to discharge any
antistatic buildup and then remove the board from its antistatic bag.
Hold the board by the edges and install it in an enclosure or place it on
the table on an antistatic surface
Install your board in your system, and wire the power supply correctly.
Failure to do so may cause the power supply unit to malfunction or
even cause permanent damage to the device.
Check all wiring connections once and then once more again
Check the antenna bias voltage and jumper correctly
Connect the GPS antenna to the OSX connectors on the GPS6160HR
Apply power to your system
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Fig. 3-1 GPS6160HR integrated in a RTD PC/104 cpuModule stack
together with a HPWR104HR power supply module and a CMM series
cpuModule
General purpose digital I/O connector
The Table 3-1 below shows the pin outs of the GPS6160HR digital I/O
interface. The signals in this geader connector can be used as generalpurpose TTL level I/O lines to interface to LCD displays, LED’s, push
buttons or relays. Note that Figure 3-2 shows two connectors together.
The connector J16 carries all inputs and J2 carries all the outputs.
PIN J2
Description
PIN J2
Description
1
3
5
7
9
GND
Out1
Out3
Out5
Out7
2
4
6
8
10
Out0
Out2
Out4
Out6
+5V
PIN J16
Description
PIN J16
Description
1
3
5
7
9
GND
In1
In3
In5
In7
2
4
6
8
10
In0
In2
In4
In6
+5V
Table 3-1 Pin outs of the GPS6160HR digital I/O interface connector
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Fig 3-2 Digital I/O connector layout of the GPS6160HR
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Chapter 4 -
HARDWARE DESCRIPTION
This chapter describes the major hardware building blocks of the GPS6160HR:
•
•
•
•
•
GPS receiver module
GPS antenna considerations
UART serial port circuitry
Digital I/O
Status LED’s
Fig. 4-1 Block diagram of the GPS6160HR
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GPS receiver
Intergarated on the GPS6160HR is an iTrax02 low power fast-fix 12channel GPS receiver from Fastrax. This GPS receiver is especially
designed for portable and mobile applications. This version of the GPS
does not support differential operation. RTD Finland can also provide
solutions for indoor navigation using pseudolites (Pseudo Satellite)
instead of satellites in the sky for positioning. In this case the standard
GPS receiver can be subsitituted by a pseudolite receiver. Application
areas include warehouse navigation.
The iTrax02 sensitivity provides continuous tracking and navigation down
to a signal level of –145 dBm and a cold start TTFF of 50 seconds (no
initialisation), 30 seconds for warm start (almanac) and one second for
quick start. Even with this performance the power consumption is
approximately 100mW with a 1s update-rate. This figure does not include
the active antenna power consumption. A complete GPS configuration
program for the iTrax02 GPS Workbench is available from the
manufacturer’s website at http://www.fastrax.fi/. This program allows you
to completely reconfigure the operation of the GPS receive. To use this
program you must configure the GPS to operate in iTalk protocol using
the RTD GPS diagnostics program.
GPS data is output only when the receiver has a fix. The GPS6160HR is
configured to output NMEA-0183 Ver 3.0 data after reset and can be
changed to binary protocol through a bit in the control register.
GPS Antenna considerations
GPS active antennas are mostly active today. The GPS6160HR accepts
either +5V or +3,3V active GPS antennas. A three-terminal header is used
to select the oprating voltage of the antenna. The internal gain of the GPS
receiver can be programmably adjusted to low-output signals or even to
interface to passive antennas. This operation is normally not needed, but
it can be done using the Fastrax GPS Workbench program.
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Fig. 4-2 GPS antenna bias voltage
A 90 degree 50 Ohm OSX connector should be selected to directly plug
into the antenna connector on the board. High quality low loss antenna
cable should be used. Try to reduce the number of connectors on the
cable to minimise signal reflections. Signal reflections on the antenna line
may cause incorrect readings for altitude information.
UART serial port circuitry
GPS data is sent and received through a standard 16C550 compatible
UART. All today’s operating systems will recognize and support this serial
communication device. The GPS6160HR uses its own onboard serial port
and will not reserve serial port resources from the system. The I/O base
address and interrupts for the serial port can be flexibly set as has been
described in previous chapters of this manual. This user’s manual will not
wade into details of serial port programming. This information is
commonly available today. You can use any communication software
package or terminal program to connect to your GPS6160HR UART. Just
make sure you set up the I/O and IRQ right. The UART on the board is
specified for full operation from –40 to +85C. The oscillator frequency is
set to be 1.8432MHz. Note that the UART interrupt can be disabled or
enabled from software by writing to bit 01 in address BASE+0x402.
The GPS receiver has two available protocols. You may select to use
either the NMEA protocol or alternatively the iTalk binary protocol. The
GPS receiver has two internal serial ports that operate in parallel. These
outputs are multiplexed into the 16C550 UART channel on the
GPS6160HR board. You may change between protocols by writing to a
control bit in the internal registers of the board. This will be described in
the later chapters of this manual.
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Digital I/O
For general-purpose digital I/O interfacing a 16-bit digital I/O port is
provided. This port includes 8 TTL-level digital outputs that are cleared (to
0) after system reset. Also are included 8 digital inputs with 10K Ohm pulldown resistors. These I/O’s are located on the left side of the board.
These I/O’s are ideal to be used to interface to LCD displays, LED’s push
buttons or other low power controls.
Status-LEDs
Two status-LEDs are provided for easy system status detection. One LED
shows the selected protocol. The other LED indicates the GPS tracking
status. Figure 4-3 below shows the location of the two LEDs.
NMEA On
Off
GPS Blinking
Off
GPS6160HR
-> NMEA protocol currently selected
-> iTalk protocol currently selected
-> GPS receives signal and is tracking satellites
-> GPS fix, tacking and all coordinates are valid.
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Chapter 5
BOARD OPERATION AND PROGRAMMING
This chapter shows you how to program and use your GPS6160HR. It
provides a general description of the I/O map. Detailed serial port
programming tips are not within the scope of this manual.
Defining the Memory Map
The memory map of the GPS6160HR occupies a group of eight bytes of
host PC I/O space. This window is freely selectable by the user as
described in Chapter 2, Table 2-2. After setting the base address you
have access to the internal resources of the GPS6160HR control logic.
These resources are not described in detail, since they are mapped as a
standard PC serial port. For more details on the EXAR ST16C550IJ44
UART chip programming please download the component specific data
from the website: http://www.exar.com/products/st16c550.html
ADDR (hex)
REGISTER
DIR
COMMENTS
BASE
TXD
O
Only if control reg. Bit 7=0
RXD
I
Only if control reg. Bit 7=0
BASE+1
BAUD div. Low
Only if control reg. Bit 7=1
BAUD div. High
Only if control reg. Bit 7=1
IRQ enable
Only if control reg. Bit 7=0
BASE+2
IRQ ID
BASE+3
Line control
BASE+4
Modem control
BASE+5
Line status
BASE+6
Modem status
BASE+400
Digital I/O
I/O
Digital I/O port
BASE+401
GPS status
I/O
Configuration registers
RESERVED
Table 5-1 General I/O map of the GPS6160HR GPS UART
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BASE+400
Digital I/O
(R/W)
This address is used to interface to the digital I/O port of the
GPS6160HR, writing to this address will transfer the data out of the output
port, while reading from this address will return the data from the digital
inputs.
BASE+401
GPS Status (R/W, 0x00 after reset)
Write
Bit 0
Bit 1
Bit 2
Bit 3
CH_SEL
GPS_RESET
RESERVED
/EN_INT
0 – NMEA mode; 1 – iTalk protocol
1 – Hard reset of GPS receiver, 0 – active
CH_SEL
GPS_RESET
GPIO8 of GPS
/EN_INT
state
state
state (Reserved for future use and testing)
state
0 – GPS interrupt enabled; 1 – disabled
Read
Bit 0
Bit 1
Bit 2
Bit 3
INTERRUPTS
What is an interrupt?
An interrupt is an event that causes the processor in your computer to
temporarily halt its current process and execute another routine. Upon
completion of the new routine, control is returned to the original routine at
the point where its execution was interrupted.
Interrupts are a very flexible way of dealing with asynchronous events.
Keyboard activity is a good example; your computer cannot predict when
you might press a key and it would be a waste of processor time to do
nothing whilst waiting for a keystroke to occur. Thus the interrupt scheme
is used and the processor proceeds with other tasks. When a keystroke
finally occurs, the keyboard then 'interrupts' the processor so that it can
get the keyboard data. It then places it into the memory, and then returns
to what it was doing before the interrupt occurred. Other common devices
that use interrupts are A/D boards, network boards, other used serial
ports etc.
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Interrupt request lines
To allow different peripheral devices to generate interrupts on the same
computer, the PC AT bus has interrupt request channels (IRQ's). A rising
edge transition on one of these lines will be latched into the interrupt
controller. The interrupt controller checks to see if the interrupts are to be
acknowledged from that IRQ and, if another interrupt is being processed,
it decides if the new request should supercede the one in progress or if it
has to wait until the one in progress has been completed. The priority
level of the interrupt is determined by the number of the IRQ as follows;
IRQ0 has the highest priority whilst IRQ15 has the lowest. Many of the
IRQ's are already used by the standard system resources, IRQ0 is
dedicated to the internal timer, IRQ1 is dedicated to the keyboard input,
IRQ3 for the serial port COM2, and IRQ4 for the serial port COM1. Often
interrupts 2,5,7,10,11 and 15 are free for the user.
8259 Programmable Interrupt Controller
The chip responsible for handling interrupt requests in a PC is the 8259
Interrupt Controller. To use interrupts you will need to know how to read
and set the 8259's internal interrupt mask register (IMR) and how to send
the end-of-interrupt (EOI) command to acknowledge the 8259 interrupt
controller.
Interrupt Mask Register (IMR)
Each bit in the interrupt mask register (IMR) contains the mask status of
the interrupt line. If a bit is set (equal to 1), then the corresponding IRQ is
masked, and it will not generate an interrupt. If a bit is cleared (equal to
0), then the corresponding IRQ is not masked, and it can then generate
an interrupt. The interrupt mask register is programmed through port 21h.
End-of-Interrupt (EOI) Command
After an interrupt service routine is complete, the 8259 Interrupt Controller
must be acknowledged by writing the value 20h to port 20h.
What exactly happens when an interrupt occurs?
Understanding the sequence of events when an interrupt is triggered is
necessary to correctly write interrupt handlers. When an interrupt request
line is driven high by a peripheral device (such as the GPS6160HR), the
interrupt controller checks to see if interrupts are enabled for that IRQ. It
then checks to see if other interrupts are active or requested and
determines which interrupt has priority. The interrupt controller then
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interrupts the processor. The current code segment (CS), instruction
pointer (IP), and flags are pushed onto the system stack, and a new set if
CS and IP are loaded from the lowest 1024 bytes of memory.
This table is referred to as the interrupt vector table and each entry to this
table is called an interrupt vector. Once the new CS and IP are loaded
from the interrupt vector table, the processor starts to execute code from
the new Code Segment (CS) and from the new Instruction Pointer (IP).
When the interrupt routine is completed, the old CS and IP are popped
from the system stack and the program execution continues from the point
where interruption occurred.
Using Interrupts in your Program
Adding interrupt support to your program is not as difficult as it may seem
especially when programming under DOS. The following discussion will
cover programming under DOS. Note that even the smallest mistake in
your interrupt program may cause the computer to hang up and will only
restart after a reboot. This can be frustrating and time-consuming.
Writing an Interrupt Service Routine (ISR)
The first step in adding interrupts to your software is to write an interrupt
service routine (ISR). This is the routine that will be executed
automatically each time an interrupt request occurs for the specified IRQ.
An ISR is different from other sub-routines or procedures. First on
entrance the processor registers must be pushed onto the stack before
anything else! Second, just before exiting the routine, you must clear the
interrupt on the GPS6160HR by writing to the Status register, and write
the EOI command to the interrupt controller. Finally, when exiting the
interrupt routine the processor registers must be popped from the system
stack and you must execute the IRET assembly instruction. This
instruction pops the CS, IP and processor flags from the system stack.
These were pushed onto the stack when entering the ISR.
Most compilers allow you to identify a function as an interrupt type and will
automatically add these instructions to your ISR with one exception: most
compilers do not automatically add the EOI command to the function, you
must do it yourself. Other than this and a few exceptions discussed below,
you can write your ISR as any code routine. It can call other functions and
procedures in your program and it can access global data. If you are
writing your first ISR, we recommend you stick to the basics; just
something that enables you to verify you have entered the ISR and
executed it successfully. For example: set a flag in your ISR and in your
main program check for the flag.
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Note: If you choose to write your ISR in in-line Assembly, you must push
and pop registers correctly and exit the routine with the IRET
instruction instead of the RET instruction.
There are a few precautions you must consider when writing ISR's. The
most important is, do not use any DOS functions or functions that call
DOS functions from an interrupt routine. DOS is not re-entrant; that is, a
DOS function cannot call itself. In typical programming, this will not happen
because of the way DOS is written. But what about using interrupts?
Consider then the following situation in your program: If DOS function X is
being executed when an interrupt occurs and the interrupt routine makes a
call to the same DOS function X, then function X is essentially being called
while active. Such cases will cause the computer to crash. DOS does not
support such operations. The general rule is that do not call any functions
that use the screen, read keyboard input or any file I/O routines, these
should not be used in ISR's.
The same problem of re-entrancy also exists for many floating-point
emulators. This effectively means that you should also avoid floating point
mathematical operations in your ISR.
Note that the problem of reentrancy exists, no matter what programming
language you use. Even, if you are writing your ISR in Assembly language,
DOS and many floating point emulators are not re-entrant. Of course there
are ways to avoid this problem, such as those which activate when your
ISR is called. Such solutions are, however, beyond the scope of this
manual.
The second major concern when writing ISR's is to make them as short as
possible in term of execution time. Spending long times in interrupt service
routines may mean that other important interrupts are not serviced. Also, if
you spend too long in your ISR, it may be called again before you have
exited. This will lead to your computer hanging up and will require a reboot.
Your ISR should have the following structure:
•
•
•
•
•
GPS6160HR
Push any processor registers used in your ISR.
Put the body of your routine here
Clear the interrupt bit by reading GPS6160HR RXD register
Issue the EOI command to the 8259 by writing 20h to 20h
Pop all registers. Most C compilers do this automatically
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The following C example shows what the shell of your ISR should be like:
/*------------------------------------------------------------------------------| Function: new_IRQ_handler
| Inputs:
Nothing
| Returns:
Nothing
|-------------------------------------------------------------------------------*/
void interrupt far new_IRQ_handler(void)
{
IRQ_flag = 1;
// Indicate to process interrupt has occurred
{
// Your program code to read UART
// read to a data buffer for example:
Guc_buffer[Gi_bufpos++] = inp(gi_SERIAL_DATA);
}
outp(0x20, 0x20); // Acknowledge the interrupt controller
}
Saving the Startup Interrupt Mask Register (IMR) and interrupt vector
The next step after writing the ISR is to save the startup-state of the
interrupt mask register, (IMR) and the original interrupt vector you are
using. The IMR is located in address 21h. The interrupt vector you will be
using is located in the interrupt vector table which is an array of pointers
(addresses) and it is locate din the first 1024 bytes of the memory
(Segment 0 offset 0). You can read this value directly, but it is better
practice to use DOS function 35h (get interrupt vector) to do this. Most C
compilers have a special function available for doing this. The vectors for
the hardware interrupts on the XT - bus are vectors 8-15, where IRQ0 uses
vector 8 and IRQ7 uses vector 15. Thus if your GPS6160HR is using IRQ5
it corresponds to vector number 13.
Before you install your ISR, temporarily mask out the IRQ you will be using.
This prevents the IRQ from requesting an interrupt while you are installing
and initializing your ISR. To mask the IRQ, read the current IMR at I/O port
21h, and set the bit that corresponds to the IRQ. The IMR is arranged so
that bit 0 is for IRQ0 and bit 7 is for IRQ7. See the paragraph entitled
Interrupt Mask Register (IMR) earlier in this discussion for help in
determining your IRQ's bit. After setting the bit, write the new value to I/O
port 21h.
With the startup IMR saved and the interrupts temporarily disabled, you
can assign the interrupt vector to point to your ISR. Again you can
overwrite the appropriate entry in the vector table with a direct memory
write, but this is not recommended. Instead use the DOS function 25h (Set
Interrupt Vector) or, if your compiler provides it, the library routine for
setting up interrupt vectors. Remember that interrupt vector 8 corresponds
to IRQ0, vector 9 for IRQ1 etc.
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If you need to program the source of your interrupts, do that next. For
example, if you are using transmitted or received messages as an interrupt
source program it to do that. Finally, clear the mask bit for your IRQ in the
IMR. This will enable your IRQ.
Common Interrupt mistakes
Remember hardware interrupts are from 8-15, XT IRQ's are numbered 0-7.
Do not forget to clear the IRQ mask bit in the IMR Forgetting to send the
EOI command after ISR code. Disables further interrupts.
Example on Interrupt vector table setup in C-code:
void far _interrupt new_IRQ1_handler(void );
#define IRQ1_VECTOR 3
void (interrupt far *old_IRQ1_dispatcher)
(es,ds,di,si,bp,sp,bx,dx,cx,ax,ip,cs,flags);
old IRQ_Vector */
void far _interrupt new_IRQ1_handler(void );
/* ISR function */
/* Name for IRQ */
/* Variable to store
/*---------------------------------------------------------------------| Function: init_irq_handlers
| Inputs:
Nothing
| Returns:
Nothing
| Purpose: Set the pointers in the interrupt table to point to
|
our funtions ie. setup for ISR's.
|----------------------------------------------------------------------*/
void init_irq_handlers(void)
{
_disable();
old_IRQ1_handler = _dos_getvect(IRQ1_VECTOR + 8);
_dos_setvect(IRQ1_VECTOR + 8, new_IRQ1_handler);
Gi_old_mask = inp(0x21);
outp(0x21,Gi_old_mask & ~(1 << IRQ1_VECTOR));
_enable();
}
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|/*---------------------------------------------------------------------| Function: restore, do this before exiting program
| Inputs:
Nothing
| Returns:
Nothing
| Purpose: Restore the interrupt vector table.
|----------------------------------------------------------------------*/
void restore(void)
{
/* Restore the old vectors */
_disable();
_dos_setvect(IRQ1_VECTOR + 8, old_IRQ1_handler);
outp(0x21,Gi_old_mask);
_enable();
}
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Chapter 6 -
GPS6160HR SPECIFICATIONS
Host interface
16-bit PC/104 bus, XT-bus used for data
GPS specifications
General
L1 frequency, C/A code (SPS)
12 independent tracking channels
Separate search and acquisition engines
Update rate
1fix/s or configurable
Accuracy
Position 10m CEP (50%)
0.2 m/s (50%)
Sensitivity
-145dBm
Status indicator
1 LED
Antenna Interface
External
Connector
Passive or active +3,3V or +5,0V BIAS
OSX, PCB mount
UART and I/O
UART compatibility
Oscillator frequency
Connection
Base addresses
Interrupts
Digital I/O
16C550
1.8432MHz
TX and RX only
32
2,5,7,10,11,12,14 and 15
8 TTL outputs, 8 TTL inputs w. 10K pull-down
GPS6160HR Electromechanical
Operating temperature range
Humidity
Altitude
Vibration
Power consumption
GPS6160HR
-40 to +85C
RH up to 95% non condensing
-1000 to 60.000 ft
Survival 10G peak
1,3W min
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Chapter 7 -
RETURN POLICY AND WARRANTY
Return Policy
If the module requires repair, you may return it to us by following the procedure listed
below:
Caution:
Failure to follow this return procedure will almost always delay repair! Please help
us expedite your repair by following this procedure.
1) Read the limited warranty, which follows.
2) Contact the factory and request a Returned Merchandise Authorization (RMA) number.
3) On a sheet of paper, write the name, phone number, and fax number of a technically
competent person who can answer questions about the problem.
4) On the paper, write a detailed description of the problem with the product. Answer the
following questions:
• Did the product ever work in your application?
• What other devices were connected to the product?
• How was power supplied to the product?
• What features did and did not work?
• What was being done when the product failed?
• What were environmental conditions when the product failed?
5) Indicate the method we should use to ship the product back to you.
We will return warranty repairs by UPS Ground at our expense.
Warranty repairs may be returned by a faster service at your expense.
Non-warranty repairs will be returned by UPS Ground or the method you select, and
will be billed to you.
6) Clearly specify the address to which we should return the product when repaired.
•
•
•
7) Enclose the paper with the product being returned.
8) Carefully package the product to be returned using anti-static packaging! We will not
be responsible for products damaged in transit for repair.
7) Write the RMA number on the outside of the package.
8) Ship the package to:
Real Time Devices Finland Oy
Lepolantie 14
FIN-00660 Helsinki
FINLAND
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Limited Warranty
Real Time Devices, Inc. warrants the hardware and software products it manufactures
and produces to be free from defects in materials and workmanship for one year following
the date of shipment from REAL TIME DEVICES. This warranty is limited to the original
purchaser of product and is not transferable.
During the one year warranty period, REAL TIME DEVICES will repair or replace, at its
option, any defective products or parts at no additional charge, provided that the product
is returned, shipping prepaid, to REAL TIME DEVICES. All replaced parts and products
become the property of REAL TIME DEVICES. Before returning any product for repair,
customers are required to contact the factory for an RMA number.
THIS LIMITED WARRANTY DOES NOT EXTEND TO ANY PRODUCTS WHICH HAVE
BEEN DAMAGED AS A RESULT OF ACCIDENT, MISUSE, ABUSE (such as: use of
incorrect input voltages, improper or insufficient ventilation, failure to follow the operating
instructions that are provided by REAL TIME DEVICES, "acts of God" or other
contingencies beyond the control of REAL TIME DEVICES), OR AS A RESULT OF
SERVICE OR MODIFICATION BY ANYONE OTHER THAN REAL TIME DEVICES.
EXCEPT AS EXPRESSLY SET FORTH ABOVE, NO OTHER WARRANTIES ARE
EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, ANY IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE, AND REAL TIME DEVICES EXPRESSLY DISCLAIMS ALL WARRANTIES
NOT STATED HEREIN. ALL IMPLIED WARRANTIES, INCLUDING IMPLIED
WARRANTIES FOR MECHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE, ARE LIMITED TO THE DURATION OF THIS WARRANTY. IN THE EVENT
THE PRODUCT IS NOT FREE FROM DEFECTS AS WARRANTED ABOVE, THE
PURCHASER'S SOLE REMEDY SHALL BE REPAIR OR REPLACEMENT AS
PROVIDED ABOVE. UNDER NO CIRCUMSTANCES WILL REAL TIME DEVICES BE
LIABLE TO THE PURCHASER OR ANY USER FOR ANY DAMAGES, INCLUDING ANY
INCIDENTAL OR CONSEQUENTIAL DAMAGES, EXPENSES, LOST PROFITS, LOST
SAVINGS, OR OTHER DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE
THE PRODUCT.
SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF INCIDENTAL
OR CONSEQUENTIAL DAMAGES FOR CONSUMER PRODUCTS, AND SOME
STATES DO NOT ALLOW LIMITATIONS ON HOW LONG AN IMPLIED WARRANTY
LASTS, SO THE ABOVE LIMITATIONS OR EXCLUSIONS MAY NOT APPLY TO YOU.
THIS WARRANTY GIVES YOU SPECIFIC LEGAL RIGHTS, AND YOU MAY ALSO
HAVE OTHER RIGHTS, WHICH VARY FROM STATE TO STATE.
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