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TMS320F280049: Nearby EPWM output signal will interfere LIN RX and break communication

Sheldon He
Expert 8585 points
Part Number: TMS320F280049

Hi expert,

My customer is using LIN to receive frames with interrupt enabled. They are facing EMI issue when nearby pins are doing EPWM output.

1. Pin 54 and pin 52 here are EPWM output, and pin 53 is LIN RX.

2. EPWM output with frequency of 170K to 200K, LIN receive at an interval of 50ms

3. Signal on LIN RX is normal in scope (turn on EPWM and turn off EPWM will get almost the same waveform)

4. If turn off EPWM output on pin 52 and pin 54, LIN receving will always come to interrupt for receiving (doing well)

5. If turn on EPWM output on pin 52 and 54, LIN receving interrupt will sometimes not enter.

6. If mapping LIN RX to some other pin far away, there will be no issue.

In error cases, we can find receving register in LIN module in not updated.

Could you give any explanation or suggestions on this?

Thanks

Sheldon 

  • 0
    TI__Mastermind 42195 points

    Sheldon,

    1. Are you using an internal or an external clock source?
    2. LIN Baud rate
      1. Verify the baud rate of your master and slave. Its possible that the baud rates are marginal and this is causing a condition where the data can be corrupted.
    3. It is very possible for PWM signals to have an effect on other near by signals, but this is very dependent on layout. 
      1. Look at how these signals are routed.
      2. How far is the ground loop for these signals?

    4. Please verify the data that is being sent  and received by the LIN module. If it is occasionally missing interrupts due to noise I would also expect it to have random errors in the data sent. 

    Regards,
    Cody