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SM320F28335-HT: Issue flashing two stacked PCBs – one board now unresponsive

Sandra Jimenez Martinez
Prodigy 40 points

Part Number: SM320F28335-HT
Other Parts Discussed in Thread: UNIFLASH

Good morning,

We were performing tests with two stacked PCBs, each containing a single microcontroller. Initially, the system was working correctly. However, when we attempted to flash one of the boards, the process failed and the PCB stopped responding. We then flashed the second board successfully, but about an hour later (without any physical changes), that board also stopped working.

The second PCB was recovered using specific boot modes (e.g., Branch to check boot mode), but the first one remains unresponsive and does not respond to tests in UniFlash.

The error we see is:

17/11/2025 12:20:07] [INFO] C28xx: GEL Output: ADC Calibration not complete, check if device is unlocked and recalibrate.[17/11/2025 12:20:07] [INFO] C28xx: Erasing Flash memory...[17/11/2025 12:20:07] [ERROR] C28xx: Flash Programmer: Error erasing flash memory. Device is locked or not connected. Operation cancelled

The only functional difference between the two boards is that on the first one, the internal ADC cannot be used due to a short between the 1.8 V analog rail and GND (we are not connecting that rail).

We have tried the following boot modes to recover the device:

  • Branch to check boot mode (worked on the second PCB)
  • Branch to SARAM, skip ADC calibration
  • Branch to Flash, skip ADC calibration

None of these have restored functionality on the first PCB.

Has anyone experienced similar behavior or can suggest a way to recover the device?

  • 0
    TI__Mastermind 27050 points

    Hi Sandra,

    Sandra Jimenez Martinez said:
    Initially, the system was working correctly. However, when we attempted to flash one of the boards, the process failed and the PCB stopped responding. We then flashed the second board successfully, but about an hour later (without any physical changes), that board also stopped working.

    Can you please help summarize what you mean by "initially the system was working"? Does this mean that at one point you were able to successfully program both of the boards and everything was working correctly? If so, what has changed between then and now?

    Sandra Jimenez Martinez said:
    The second PCB was recovered using specific boot modes (e.g., Branch to check boot mode), but the first one remains unresponsive and does not respond to tests in UniFlash.

    Is it possible to swap the units on the two boards to further isolate the issue?

    Sandra Jimenez Martinez said:
    We then flashed the second board successfully, but about an hour later (without any physical changes), that board also stopped working.

    What do you observe when the board has stopped working or how are you concluding that the board is no longer functional?

    Best Regards,

    Marlyn

  • 0 in reply to Marlyn Rosales Castaneda20
    Prodigy 40 points

    Hi Marlyn!

    Marlyn Rosales Castaneda20 said:
    Can you please help summarize what you mean by "initially the system was working"? Does this mean that at one point you were able to successfully program both of the boards and everything was working correctly? If so, what has changed between then and now?

    Exactly. It was working and nothing changed except for trying to flash one of the  PCBs

    Marlyn Rosales Castaneda20 said:
    Is it possible to swap the units on the two boards to further isolate the issue?

    The microcontrollers are soldered and trying to change them may cause more problems (we dont want to risk it having one of them working)

    Marlyn Rosales Castaneda20 said:
    What do you observe when the board has stopped working or how are you concluding that the board is no longer functional?

    The power consumption dropped significatively and we were not able to flash nor recognize the device on code composer. We tried to use uniflash to test it but it was not working either.

    Is it possible that trying to flash one of them while they were stacked may have caused some trouble? We have picked another pcb as we could not fix it and we should stack them but I'm not sure about it anymore. The one that we could recover was not the one that we tried to flash initially and maybe it was affected by it. I'm not sure.

    Thank you for helping me.

    Best regards

  • 0 in reply to Sandra Jimenez Martinez
    TI__Mastermind 27050 points

    Hi Sandra,

    Thank you for providing more insights. Can you please describe how these two boards are stacked together? What are the connections between these two boards? Also, what is your method for flashing the boards? Do you have a JTAG connection on there?

    Best Regards,
    Marlyn