Timing Issues When Writing to Disconnected CAN channel

[dominic_v]

Hello,

I am running an application based on the 31_SIMPLE_TCP_SERVER example.

My modification involves sending a test CAN message out of a port periodically from a RTX thread.

If I have a CAN device connected, I can transmit as fast as I like (say every one millisecond)

However, if I disconnect the CAN port, it seems to create an additional load on the RTOS and causing error. Specifically, I'm receiving the osRtxErrorTimerQueueOverflow error.

I expect the CAN_Write function to return the CAN_ERR_TX_FULL, but I didn't expect it to cause any additional timing issues with my system.
I checked the delta time to the call to CAN_Write, and it is consistent regardless of if another CAN device is connected or not. This makes sense as there are no while loops in the function.

Is there any added interrupt load that the FPGA introduces when sending to a disconnected CAN network?

Thanks,
Dominic

[PEAK-Support]

If you disconnect the CAN cable without leaving a termination resistor on the Router the CAN Controller might see a Bus-OFF event due to improper signaling
(valid signal levels need a term-resistor). Here the CAN Controller generates a status frame showing Bus-OFF ( see can_user.c) .
There the CAN Controller is re-initialized, Firmware will continue transmission but again ending in a Bus-OFF situation. So you may get an endless loop here.

Try either to keep a termination on the Router's DSUB ( max. two status frames seen until error-passive), or modify your can_user.c to use a different handling in case of a Bus-OFF event.

[dominic_v]

I tried adding an external termination, and both an external and the internal, but it didn't make any difference.

Looking an my can_user.c (see attached), I only see what looks like re-initialization in the CAN_UserRead() function.
However, I'm not even doing any reads at all and I don't see any other calls to CAN_UnInitialize() or CAN_Initialize() other than at start up.

Any other ideas?

[P.Steil]

the FPGA do not have any IRQ support yet. All data must be polled. You can check the following:

> Check if you have FPGA version 10 ( macro HW_FPGA_VERSION can be used for reading)
> If you read CAN data, do this from just a single point e.g. single thread
> Check your CAN_Write() and other functions. Typical examples the basic code is not thread save.
E.g. CAN_Write() from two threads may destroy data integrity

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