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TMS320F28335: DSP28335 black screen issue

ian wu
Intellectual 965 points

Part Number: TMS320F28335

hi  expert

1. Definition
The so-called "white screen" refers to the situation where the operation panel cannot establish a 232 serial communication with the DSP normally; this causes the panel to repeatedly attempt to connect with the DSP and result in continuous restarts; the same panel can communicate normally with the DSP and display content on a normal DSP control board, so the problem is not related to the panel itself; the problem points to the control board.

2. The process of the white screen appearance
The white screen always appears after power is turned off and then turned on again;
One type of white screen situation: When the parameter settings were saved before the screen went black, and the screen went black again after power was turned off and then turned on, there was a certain probability of this happening. Even after repeating the process of turning off the power and then turning it on dozens of times, the screen remained in the white screen state;
After connecting the emulator, read the parameter save area of the external device Flash and maintain it for a period of time, and the normal display can be restored; However, when the emulator is disconnected, the white screen reappears;
The parameters in the parameter save area read by the emulator were accidentally erased. Parameter erasure may cause the white screen? 
A white screen situation: Manually power off the device while keeping the parameters saved, causing the DSP to erase the saved parameter area in the peripheral flash memory; when power is restored after a power-off, there is a certain probability of triggering a white screen; however, it is different from the previous white screen; normal communication can be restored after multiple power-offs and power-ups.

3. Communication mechanism between the panel and the DSP
After the system initialization in the DSP and the initialization of all peripheral devices are completed, the SCI serial port for communication with the panel 232 is configured; the SCIa port is used, with fixed parameter configuration. There is no need to obtain external parameters such as reading parameters from the flash after configuration, and even if the external flash parameter area is accidentally erased, it will not affect the communication of SCIa.

4.    Questions
1. The reading and writing of external Flash is handled by the xintf module. Could there be any erroneous operations by the xintf module?
2. Under what circumstances will the DSP enter a suspended state?

  • 0
    TI__Mastermind 25980 points

    Hello,

    Please note that a "white screen" symptom on its own is quite broad and could stem from many different areas of the system (e.g. display workflow, clocking, power sequencing, SCI/communication issues, etc.).

    To help narrow this down from a peripheral/register perspective, could you help provide more details? For example:

    • At what point does the white screen appear? (boot, after OS loads, after a specific application starts)
    • Have you compared device register settings between the working and non-working cases? Specifically, if this is SCI related, the SCI status and error registers.
    • Have you verified power rail measurements- are voltages stable? Device running normally other than potential SCI communication errors?
    • Is this an existing system and you just now are encountering this issue? Have you made any recent changes to firmware, configuration, or hardware?

    In the meantime, here are some debug steps that may help isolate the issue:

    1. Verify SCI serial comms status- status, and error count registers for any indication of communication failure. 
    2. Review general interrupt/error status registers- look for underflow, overflow, CRC errors, or FIFO errors in the display and communication peripherals
    3. Confirm pinmux configuration- incorrect mux settings can result in signals not reaching the display
    4. Check initialization sequence ordering- some display interfaces are sensitive to the order of power, clock, and data enable sequencing

    A white screen often means the display backlight and power are working, but valid data isn't arriving. Please let me know when you are able to share more details to help narrow down the cause.  

    Best Regards,

    Allison