CAN Message Definition

The open source repository does not include the implementation of the functions declared in signals.h and these are required to compile and program a CAN transaltor. These functions are dependent on the specific vehicle and message set, which is often proprietary information to the automaker.

Once the libraries are installed and you run make, you’ll notice that it won’t compile - you’ll get a bunch of errors about undefined references to functions from signals.h:

build/pic32/cantranslator.o: In function `updateDataLights()':
cantranslator.cpp:(.text._Z16updateDataLightsv+0x20): undefined reference to `openxc::signals::getCanBusCount()'
cantranslator.cpp:(.text._Z16updateDataLightsv+0x48): undefined reference to `openxc::signals::getCanBusCount()'
cantranslator.cpp:(.text._Z16updateDataLightsv+0xd4): undefined reference to `openxc::signals::getCanBuses()'
build/pic32/cantranslator.o: In function `initializeAllCan()':
cantranslator.cpp:(.text._Z16initializeAllCanv+0x1c): undefined reference to `openxc::signals::getCanBuses()'
cantranslator.cpp:(.text._Z16initializeAllCanv+0x30): undefined reference to `openxc::signals::getCanBusCount()'
build/pic32/cantranslator.o: In function `setup':
cantranslator.cpp:(.text.setup+0x14): undefined reference to `openxc::signals::initialize()'
build/pic32/cantranslator.o: In function `receiveRawWriteRequest(cJSON*, cJSON*)':
cantranslator.cpp:(.text._Z22receiveRawWriteRequestP5cJSONS0_+0x3c): undefined reference to `openxc::signals::getCanBuses()'
build/pic32/cantranslator.o: In function `receiveTranslatedWriteRequest(cJSON*, cJSON*)':
cantranslator.cpp:(.text._Z29receiveTranslatedWriteRequestP5cJSONS0_+0x44): undefined reference to `openxc::signals::getSignals()'
cantranslator.cpp:(.text._Z29receiveTranslatedWriteRequestP5cJSONS0_+0x4c): undefined reference to `openxc::signals::getSignalCount()'
cantranslator.cpp:(.text._Z29receiveTranslatedWriteRequestP5cJSONS0_+0x78): undefined reference to `openxc::signals::getSignals()'
cantranslator.cpp:(.text._Z29receiveTranslatedWriteRequestP5cJSONS0_+0x80): undefined reference to `openxc::signals::getSignalCount()'
cantranslator.cpp:(.text._Z29receiveTranslatedWriteRequestP5cJSONS0_+0xe4): undefined reference to `openxc::signals::getCommands()'
cantranslator.cpp:(.text._Z29receiveTranslatedWriteRequestP5cJSONS0_+0xec): undefined reference to `openxc::signals::getCommandCount()'
cantranslator.cpp:(.text._Z29receiveTranslatedWriteRequestP5cJSONS0_+0x10c): undefined reference to `openxc::signals::getSignals()'
cantranslator.cpp:(.text._Z29receiveTranslatedWriteRequestP5cJSONS0_+0x114): undefined reference to `openxc::signals::getSignalCount()'
build/pic32/cantranslator.o: In function `receiveCan(openxc::pipeline::Pipeline*, CanBus*)':
cantranslator.cpp:(.text._Z10receiveCanPN6openxc8pipeline8PipelineEP6CanBus+0x54): undefined reference to `openxc::signals::decodeCanMessage(openxc::pipeline::Pipeline*, CanBus*, int, unsigned long long)'
build/pic32/cantranslator.o: In function `loop':
cantranslator.cpp:(.text.loop+0x2c): undefined reference to `openxc::signals::getCanBuses()'
cantranslator.cpp:(.text.loop+0x44): undefined reference to `openxc::signals::getCanBusCount()'
cantranslator.cpp:(.text.loop+0x90): undefined reference to `openxc::signals::getCanBuses()'
cantranslator.cpp:(.text.loop+0xa4): undefined reference to `openxc::signals::getCanBusCount()'
cantranslator.cpp:(.text.loop+0xd4): undefined reference to `openxc::signals::loop()'
build/pic32/main.o: In function `main':
main.cpp:(.text.main+0x60): undefined reference to `openxc::signals::getActiveMessageSet()'
build/pic32/main.o: In function `handleControlRequest(unsigned char)':
main.cpp:(.text._Z20handleControlRequesth+0x64): undefined reference to `openxc::signals::getActiveMessageSet()'
main.cpp:(.text._Z20handleControlRequesth+0x8c): undefined reference to `openxc::signals::getActiveMessageSet()'
build/pic32/platform/pic32/canutil.o: In function `openxc::can::initialize(CanBus*)':
canutil.cpp:(.text._ZN6openxc3can10initializeEP6CanBus+0xbc): undefined reference to `openxc::signals::initializeFilters(unsigned long long, int*)'
build/pic32/platform/platform.o: In function `openxc::platform::suspend(openxc::pipeline::Pipeline*)':
platform.cpp:(.text._ZN6openxc8platform7suspendEPNS_8pipeline8PipelineE+0x3c): undefined reference to `openxc::signals::getCanBuses()'
platform.cpp:(.text._ZN6openxc8platform7suspendEPNS_8pipeline8PipelineE+0x50): undefined reference to `openxc::signals::getCanBusCount()'
collect2: ld returned 1 exit status
make: *** [build/pic32/cantranslator-pic32.elf] Error

You have three options to get a working vehicle interface:

• Use a pre-built binary firmware from an automaker
• Create a message set mapping and use the OpenXC Python library to auto-generate an implementation of signals.h. Knowledge of the vehicle’s CAN message is required for this method.
• Implement the signals.h functions manually

Auto-generated from Mapping

The code generation tools are documented in the code generation input definitions.

Once you’ve defined your message set in a JSON file, install the OpenXC Python library, then run the openxc-generate-firmware-code tool to create an implementation of signals.cpp:

cantranslator/ $ openxc-generate-firmware-code --message-set mycar.json > src/signals.cpp

The firmware should now compile! Don’t modify the signals.cpp file manually, since it’s generated you should expect it to be wiped and recreated at any time; always make changes to the JSON instead.

Manual Implementation

You must implement the functions defined in the signals.h header file. The documentation of those functions describes the expected effect of each. Implement these in a file called signals.cpp and the code should now compile.

You must know the CAN message formats of the vehicle you want to use with the vehicle interface, as you cannot implement these functions without that knowledge.