BUS OFF state can not be triggered

[witness]

hi, experts

I am working on S32K324, and use below method test CAN bus off:

1) CANH connect to VCC

2) CANH connect to GND

3) CANL connect to VCC

4) CANL connect to GND

5) CANH connect to CANL

but the last case is failed, that means although CANH&CANL connected, the CAN bus off interrupt can not reached, can TXERRCNT does not increase, does anyone has encountered such issue?

[Senlent]

Hi@witness

please take a look at the S32K3XXRM_rev7->Chapter 74.6.2.8 Error Counter(ECR)

You can try to test and short-circuit CAN-H and CAN-L during normal communication between the two nodes.

[witness]

hi, @Senlent 

Thanks for your reply. I am a little confused the concept for "two node", in fact, we are using Vector CANoe tool to do the test, and if we connect CANH to GND, the error frame will constantly occurs, so bus off state can be reached, but why CANH&CANL connect will not trigger bus off.

[Senlent · Accepted solution]

Hi@witness

First of all, if CAN-H and CAN-L are short-circuited during transmission, the node will definitely enter the bus-off state.

for one node:

there is only one transmission node on the bus, and it cannot get ACK from other nodes.

You can reproduce this situation，for example.

You can disconnect from the bus and then try to send a frame, then it will enter this state. At this time, if you connect CAN-L or CAN-H, it will not enter the bus-off state.