Colíbri iMX7D flexcan doesn't work

Technical Support
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1

I’m testing the flexcan_network example for the colibri iMX7 on the cortex-m4. During the execution process the BOARD_FLEXCAN_HANDLER method / flexcan1 interrupt handler was never executed. The program itself is working correctly except the send and receive interrupt.

Additionally I checked the values of the following internal registers of the cortex-m4 for the flecan 1.

  • CAN_MCR_REG - 0000 0000 0000 0000 0000 0000 0000 1111
  • CAN_CTRL1_REG - 0000 0001 1111 1111 0000 0000 0000 0110
  • CAN_CTRL2_REG - 0000 0000 0000 0000 0000 0000 0000 0000
  • CAN_IMASK1_REG - 0000 0000 0000 0000 0000 0000 0000 0000
  • CAN_IFLAG1_REG - 0000 0000 0000 0000 0000 0000 0000 0000
  • CAN_ESR1_REG - 0000 0000 0000 0100 0100 0010 0101 0110
  • CAN_ECR_REG - at each program iteration the value changes

Does anyone know how to solve this problem or has some advice for a flexcan configuration?

Thanks for the help.

2

Dear @developerTirol

I was not able to reproduce your problem. I hooked a CAN Analzer (CANdoISO) up to the Evaluation board and was successfully able to transmit and receive messages. Let me describe my setup and point out some common pitfalls…

#Setup

  1. The Colibri Evaluationboard needs to
    be configured properly. Please refer
    to the document below for details:

  2. On my PC I had 2 terminal programs running: one for
    UARTA, one for UARTB

  3. I booted the Colibri into U-Boot and started a dummy M4 application which does nothing but looping forever. This is my standard procedure to turn on all required clocks, so I can later easily hook up the JTAG debugger.

  4. I started the CAN Analyzer, making sure that

  • The baud rate was correctly set to 125kbps
  • The analyzer was in “normal” mode (not in “ListenOnly”)
  1. I used VSCode to build the flexcan_network project in debug configuration, and to download and run it through the JTAG debugger.

Now I was able to see the debug messages on UARTB, showing that the application was transmitting a CAN message once every second.
Using the CAN analyzer I transmitted messages with ID 0x321 and was able to see on UARTB that these messages were received properly.

DLC=1, mb_idx=0x123
RX MB data: 0x9

DLC=1, mb_idx=0x123
RX MB data: 0xa

DLC=8, mb_idx=0x321
RX MB data: 0xff ff ff ff ff 0 0 0

Further Hints

Some common pitfalls could be:

  • The CAN bus needs to be terminated
  • It is crucial that there is an active second CAN device on the bus. This is required to acknowledge transmitted messages.
  • If you abort the application while running (for example with the debugger), restarting the application is not always sufficient to bring the CAN controller back in a proper state. If you see inproper functioning, I recommend to do a power cycle and start over
  • Linux could possibly lock some resources once it is started. Try to run the application from U-Boot.

Regards, Andy