[En-Nut-Discussion] ATCAN repeats messages on Error

Henrik Maier hmlists at focus-sw.com
Sat Sep 16 02:04:00 CEST 2006

Uwe Bonnes wrote:
> Hallo,
> with my CAN Setup with a long, unterminated line, I can get the Ethernut
> AT90CAN128 to repeatedly send the message, hogging the CAN Bus. 
> My program definitly only sends the message once.
> I know, an unterminated line is an user error, but the Ethernut driver
> should not hog the line in such an error.
> Any ideas how to handle this error more gracefully?

Never observed this issue and the controller should go bus-off after 
repeated line faults to prevent exactly this.

In case there is no other node on the bus, the unit should have an ACK 
error and go error-passive after 127 failed transmissions and bus-off 
after 255.

I am happy to assist with the fault analysis and also to improve the 
driver if we find an issue in the driver.

Can you put some debug instrumentation in your arch/avr/dev/atcan.c code 
in AtCanSendMsg and AtCanOutput to see what the driver actually does?

In particular I am interested if we get a TX interrupt and also the 
status of the CAN Transmit Error Counter Register - CANTEC.


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