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TMS320F280049: GPIO32 unexpected pulled to high after bring up

Part Number: TMS320F280049

Hi expert,

My customer find GPIO32 is unexpected pulled high after device start up. This pin have external connection like below.

Do you have any idea on what could be the cause?

Thanks

Sheldon

  • Sheldon,

    Did you try to remove the two resistors so see if that changes the state of GPIO32 after reset?

    REgards,
    Peter

  • Hi Peter,

    We do below test:

    Configure GPIO32 muc to CAN but didn't enable CAN, internal pull up enabled.

    If we removed the 100ohm in above circuit.

    GPIO is measured 0V and isolator input is 3V.

    If we connected the 100ohm in above circuit.

    Both GPIO and isolator input is measured 3.3V

    Could you help us with that?

    Thanks

    Sheldon

  • Sheldon,

    Looks to me like with the 100Ohm resistor removed the MCU side is acting properly. Seems that your issue is that the input to the isolator seems to be driving enough current to overcome the 5K resistor to ground. The only thing I can suggest is to look at the VCC1 and GND1 pins to verify their state. Otherwise I would suggest to contact the Isolator group that knows this device much better.

    Regards,

    Peter

  • Hi Sheldon,

    Another potential thing to investigate:

    GPIO24 & GPIO32 are this device's default boot mode pins.

    Based on the image, GPIO24 doesn't look to be pulled either high or low.  Does pulling GPIO24 low or high change the behavior you are witnessing on GPIO32?

    What boot mode is desired?


    Thank you,
    Brett

  • Hi Brett,

    They used to like configure OPT to zero boot to flash, but now also try booting to flash with current external connection.

    GPIO24 do left float in their design, I have advised them to have a try here. They captured GPIO24 in low state since power up, but I still recommend them to tie GPIO24 low to have a try.

    They desire boot to flash directly or indricetly. They are trying boot to flash with GPIO24 low and GPIO32 high which seem impossible with SCI not configured to do any communication.

    I will also connect isoltor team for this issue.

    Thanks 

    Sheldon

  • Hi Sheldon,

    Note that if GPIO24 is high & GPIO32 is low, that will boot the device into a CAN boot-mode on this device.
    (unless they edit the way the boot pins work via the OTP)


    Thank you,
    Brett