eeb8585087
3ca654f move acura rdx to generator folder
1c7c490 move pilot touring to generated
89856dd fix bugs in some counter/checksum definitions
451a2b4 honda wheelspeed in kph to match toyota
290dd14 rename generic honda and toyota dbcs to include year
ccb8a14 readded gas interceptor to hondas so it does not break regression tests
66d256e readme explanation of preprocessor
6c8d9f7 regenerate new steer torque eps factor
beba6d5 move generated files to root folder
2b5b0aa Toyota: different factor for STEER_TORQUE_EPS
e41b174 fix typo
682f557 cleanup
1faf67c fix crv steering_control message
cce6c79 add odometer message to civic and odyssey
74cc834 fix PCM_SPEED factor
3f2baa5 fix honda dometer scaling
f6fd6b9 fix comments and values
f0ba5e2 whitespace consistency
8c77a5d dbc file preprocessor
10f8c6e consistent can message names for supported Hondas
af07d6a Topyota Corolla: added dbc file, seems the same as Rav4
a632fde Cleanup duplicate message names
git-subtree-dir: opendbc
git-subtree-split: 3ca654f88545d05bf23cb8ff945f06a28c32902e
old-commit-hash: 852166f5cc
3.0 KiB
opendbc
The project to democratize access to the decoder ring of your car.
DBC file basics
A DBC file encodes, in a humanly readable way, the information needed to understand a vehicle's CAN bus traffic. A vehicle might have multiple CAN buses and every CAN bus is represented by its own dbc file. Wondering what's the DBC file format? Here a good overview.
How to start reverse engineering cars
opendbc is integrated with cabana.
Use panda to connect your car to a computer.
DBC file preprocessor
DBC files for different models of the same brand have a lot of overlap. Therefore, we wrote a preprocessor to create DBC files from a brand DBC file and a model specific DBC file. The source DBC files can be found in the generator folder. After changing one of the files run the generator.py script to regenerate the output files. These output files will be placed in the root of the opendbc repository and are suffixed by _generated.
Good practices for contributing to opendbc
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Comments: the best way to store comments is to add them directly to the DBC files. For example:
CM_ SG_ 490 LONG_ACCEL "wheel speed derivative, noisy and zero snapping";is a comment that refers to signal
LONG_ACCELin message490. Using comments is highly recommended, especially for doubts and uncertainties. cabana can easily display/add/edit comments to signals and messages. -
Units: when applicable, it's recommended to convert signals into physical units, by using a proper signal factor. Using a SI unit is preferred, unless a non-SI unit rounds the signal factor much better. For example:
SG_ VEHICLE_SPEED : 7|15@0+ (0.00278,0) [0|70] "m/s" PCMis better than:
SG_ VEHICLE_SPEED : 7|15@0+ (0.00620,0) [0|115] "mph" PCMHowever, the cleanest option is really:
SG_ VEHICLE_SPEED : 7|15@0+ (0.01,0) [0|250] "kph" PCM -
Signal's size: always use the smallest amount of bits possible. For example, let's say I'm reverse engineering the gas pedal position and I've determined that it's in a 3 bytes message. For 0% pedal position I read a message value of
0x00 0x00 0x00, while for 100% of pedal position I read0x64 0x00 0x00: clearly, the gas pedal position is within the first byte of the message and I might be tempted to define the signalGAS_POSas:SG_ GAS_POS : 7|8@0+ (1,0) [0|100] "%" PCMHowever, I can't be sure that the very first bit of the message is referred to the pedal position: I haven't seen it changing! Therefore, a safer way of defining the signal is:
SG_ GAS_POS : 6|7@0+ (1,0) [0|100] "%" PCMwhich leaves the first bit unallocated. This prevents from very erroneous reading of the gas pedal position, in case the first bit is indeed used for something else.