After building the CAN sniffer with Elduino CAN128 board I wanted to see CAN messages in my old Ford Mondeo.
After connecting the board to OBD2 connector and turning on the ignition I started seeing quite a few packets. This is a very good sign - it shows that the board is connected properly, CAN baud rate is correct and that the Arduino software works.
However, I have made a mistake when defining/passing the variable for message count, thus some of the counts show negative values. At the moment I am more interested in CAN message id's and data. At the beginning it looks like a lot of random numbers that make no sence. However, trying to play around with knobs, pedals and buttons makes the image a lot more clear. First of all I wanted to figure out if there is a message containing gas pedal position. This is the easiest data to spot - just pres/release the pedal and look for changing numbers in the screen. After pressing the pedal I saw that bytes D6-D7 change in the packet with ID 0x201. I saw that the value range is between 0x0000 and 0xc800, D6 is a high byte and D7 is low. Doing the same thing with all other inputs I have figured out the steering wheel position data, hand brake status an more:
CAN ID | D0 | D1 | D2 | D3 | D4 | D5 | D6 | D7 | Comments |
0x80 | SWH | SWL |
SteeringPositionSensor SW - steering wheel position in 0.1 degrees (90 degrees = 900) |
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0x201 | RPMH | RPML | SPEED | GASH | GASL |
RPM - engine RPM multiplied by 4 (4000=1000RPM)
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0x440 | AC? |
AC control module AC? = 0x80 when AC is on (bit 7 - AC state) |
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0x430 | HB? | HB? = 0x20 when hand brake is on (bit 5 - hand brake state) |
Here is the screenshot of serial terminal with registered CAN messages
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