So I followed the recommendation and:
1_ copied the sketch coryjfowler Update CAN_receive.ino
2_ according to the image, I went back to following the same steps in the code change.
3_ connected the GND of the source that supply the dashboard in connection with the arduino that supply the MCP. So the GNDs are all connected.
4_ loaded the program to UNO with the same keys turned on (3 & 4) All ok with the loading.
5_ I turned on the power supply and the oscilloscope started to detect CAN communication measured on the MCP board.
6_ I opened the "serial monitor" with 115200baud, just like what was written on the sketch. The result is this (see the image): no communication appears.
7_ changed the CAN L & CAN H cables but it stayed the same. I am sure that the cables are right connected because I have the dashboard wireframe and the pin function.
8_ seeing the oscilloscope, I check the data I send in the image. It may not be 100% strict. I would like to know how to calculate the baud to confirm that 115200 value. If the measure of a single bit is the same in both CAN (High and Low), I think it's 4,5V = VPP??
9_ if the crystal in dashboard has not the same value, why we use 8MHZ?
10_ I read that this dashboard follows the FIAT CAN B protocol.
CAN B is a low speed protocol (125Kbps).
The signal follows the same pattern as the signal I get from the oscilloscope as you can see in the link:
Do I have to change the communication speed where it says 500kbps? Or elsewhere?
thanks in advance