When CAN_H short to ground the Bus is not shut off all the time, for a while communction is ok, for a while the bus shut down.

user5308603

Prodigy 50 points

Other Parts Discussed in Thread: TMS320F28035

Enter the Bus-off state we have three ways:

1. CAN_L short to Battery

2. CAN_H short to CAN_L

3. CAN_H short to ground

when 1 and 2 happened the bus enter bus-off state and the bus shut down,there have no message send out on the CAN bus. But the third method(CAN_H short to ground) CAN bus not shut off all the time, for a while communction is ok, for a while the bus shut down.

In CAN driver I set the ABOTestCaseData.zip

ECanaShadow.CANMC.bit.ABO = 1; // Auto bus on

over 7 years ago

0 Ramesh Ramamoorthy over 7 years ago

TI__Mastermind 27240 points

What is the concern?

0 Hareesh Janakiraman over 7 years ago in reply to Ramesh Ramamoorthy

TI__Guru* 95315 points

What transceiver are you using?

0 user5308603 over 7 years ago in reply to Hareesh Janakiraman

Prodigy 50 points

Hi Hareesh,

We use TJA1044.

By the way before the TJA1044, we used TJA1042,both of them have the same issue.

0 user5308603 over 7 years ago in reply to Ramesh Ramamoorthy

Prodigy 50 points

My concern is that: if have this issue the third phenomenon can't meet customer's requirement of bus-off recovery. 1 and 2 can meet customer's requirement.

0 user5308603 over 7 years ago

Prodigy 50 points

TestCaseData.zip have the CAN message log for your reference. There have three files, include "CAN_H short to CAN_L.asc","CAN_H short to ground.asc","CAN_L short to Battery.asc".

0 user5308603 over 7 years ago in reply to user5308603

Prodigy 50 points

Hi Hareesh,

I think there is no correlation with which transceiver to be used,when can I get your feedback?

Look forward to your reply.

0 Walsh over 7 years ago in reply to Ramesh Ramamoorthy

Intellectual 950 points

Hi Ramesh:

DSP: TMS320F28035
Transceiver: TJA1044
Our concern is how can bus enter bus-off status when "CAN_H short to ground" . The phenomenon is bus doesn't complete off when "CAN_H short to ground".
Do you have any suggestion?
Thanks
Walsh

0 Sunny Qin over 7 years ago in reply to Hareesh Janakiraman

TI__Expert 4890 points

Hi Hareesh,

This is an important customer for us, could you help to give some comments for this issue?

Thanks so much.

Regards, Sunny

0 Ramesh Ramamoorthy over 7 years ago in reply to Sunny Qin

TI__Mastermind 27240 points

Sunny,
The query is moved to another expert and he may respond when he gets a chance. If the thread is active when Hareesh is back, he can chime in. Thanks.

0 Hareesh Janakiraman over 7 years ago in reply to Ramesh Ramamoorthy

TI__Guru* 95315 points

I checked this with an expert in transceiver group and got the following feedback:

"If CANH is shorted to GND, then there will be no positive differential voltage. The CAN bus requires CANH to be +900mV above CANL for logical zero state. If CANH is at 0V, CANL would need to be close to -1V to create a dominant bit. So I am not sure how there will even be communication for a while.”

Is this a high-impedance short to GND, as opposed to a direct 0Ω short to ground? Could you please provide a oscilloscope shot of CANTX, CANRX, CANH, and CANL pins, when the fault is simulated?

0 Hareesh Janakiraman over 7 years ago in reply to Hareesh Janakiraman

TI__Guru* 95315 points

Hello,
Has this issue been resolved? If so, please close the post.

0 Hareesh Janakiraman over 7 years ago in reply to Hareesh Janakiraman

TI__Guru* 95315 points

Hello,
I haven't seen further response on this. I presume the issue has been resolved. Please close the post if this is the case.

C2000™︎ microcontrollers

C2000 microcontrollers forum

When CAN_H short to ground the Bus is not shut off all the time, for a while communction is ok, for a while the bus shut down.