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TMS320F280041: The SCI TX pin is always pulled low when there is interference

Katherine Wang
Intellectual 2210 points
Part Number: TMS320F280041


Hi Team,

Hardware: DSPTMS320F280041 as the main control power converter

SCI isolation communication

Software: query mode FIFO receive FIFO transmission with no interrupt used

Symptoms:

  1. The DSP SCI can communicate normally with the outside world when the power is not turned on.
  2. When the load is switched after the power is turned on (27-52A), the SCI communication loss will occasionally occur. The SCI TX pin of the DSP has been pulled down and cannot be recovered automatically. After testing, it turns out to have nothing to do with the receiver (the receiver reset cannot release this state). Communication resumes after the DSP is powered on and reset again.
  3. Receiver RX has an internal pull-up resistor.
  4. The development environment cannot use the emulator to debug online, and I cannot view the register status.

Could you please help analyze the possible reasons and solutions? Thank you.

Kind regards,

Katherine

  • 0
    TI__Mastermind 25800 points

    Hi Katherine,

    Katherine Wang said:
    The DSP SCI can communicate normally with the outside world when the power is not turned on.

    Can you please elaborate on which power source you are referring to?

    Katherine Wang said:
    When the load is switched after the power is turned on (27-52A), the SCI communication loss will occasionally occur. The SCI TX pin of the DSP has been pulled down and cannot be recovered automatically. After testing, it turns out to have nothing to do with the receiver (the receiver reset cannot release this state). Communication resumes after the DSP is powered on and reset again.

    What is the load connected to (ie. which device pin)?

    So the issue is that the device can no longer transmit since the tx line is pulled low somehow? Or it suppose to receive as well and its not doing that?

    Katherine Wang said:
    Receiver RX has an internal pull-up resistor.

    This is the RX pin on the F28004x side?

    What is the operation of the device overall? Are other components functioning okay or are there any other issues?

    Best Regards,
    Marlyn

  • 0 in reply to Marlyn Rosales Castaneda20
    TI__Intellectual 2210 points

    Hi Marlyn,

    Marlyn Rosales Castaneda20 said:
    which power source you are referring to?

    LLC power supply, input 300V and output 12V. While the output is 12V, it is connected to CR mode switch.

    Marlyn Rosales Castaneda20 said:
    the device can no longer transmit since the tx line is pulled low somehow? Or it suppose to receive as well and its not doing that?

    Yes, the tx line is pulled low. It can no longer send, but the reception is normal.

    Marlyn Rosales Castaneda20 said:
    This is the RX pin on the F28004x side?

    The RX pin of another MCU chip is not F28004x.

    Other components of the device are functioning normally.

    Best Regards,
    Katherine

  • 0 in reply to Katherine Wang
    TI__Mastermind 25800 points

    Hi Katherine,

    Katherine Wang said:
    Yes, the tx line is pulled low. It can no longer send, but the reception is normal.

    Is there any connection between the SCI and other components that could be causing this interference? 

    Best Regards,

    Marlyn