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TMS320F28035: An empty CAN frame is always transmitted first after power up

Part Number: TMS320F28035

Hi team,

This is a question we observed during tuning CAN function in customer's system.

For testing, customer is transmitting a CAN frame with the following functions:

Then, they performed 4 CAN frame transmitting:

UINT8 u8testDataBuf1 = {1,1,1,1,1,1,1,1};

UINT8 u8testDataBuf2 = {2,2,2,2,2,2,2,2};

MailBoxWrite(0, u8testDataBuf1, 8);

MailBoxWrite(0, u8testDataBuf1, 8);

MailBoxWrite(0, u8testDataBuf2, 8);

MailBoxWrite(0, u8testDataBuf2, 8);

Here is what they captured with CAN analysis:

1  length 0,No data (with correct ID)

2  length 8:1,1,1,1,1,1,1,1 (with correct ID)

3  length 8:1,1,1,1,1,1,1,1 (with correct ID)

4  length 8:2,2,2,2,2,2,2,2 (with correct ID)

So, basically, they MCU will always send a empty frame and then previous frame.

Is this the normal way F82035 CAN works? 

Thanks,

Brian