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NAK after a while

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  • NAK after a while

    I am working with a 2.4'' picaso LCD with a serial com with a STM32F303 as host.
    The baudrate is 115200.
    All is working properly during more than half hour, but after a time, I only reveived NAK from the Picaso.
    I have monitored the serial line to the Picaso and I can not see any change. The CRC is correct.
    If I reset the host, all restart properly. it meens that the problem come from the host but I don't know where.
    Is the Picaso serial hw is more sensistive than my simple Serial/USB transceiver?
    Do I have to wait between 2 commands to avoid Picaso buffer overflow?
    Many thanks for any advise

  • #2
    i presume you have a custom library? if you send more data than the lcd can process before receiving the ack of completion, this will overflow the display buffer and itll return NAKs, EVEN IF your crc’s are good, this is because the uart buffer on lcd is out of sync once overflow occured, you could macguiver a 0xFF push every few NAKs and it will eventually recover, but this is just a bandaid and not recommended. if you want to continue this way, its highly recommended to not send data faster than 25-40 ms to the display if you continue to ignore the ACKs, but its a performance hit for you as some commands take less time than others to process, depending on the widget


    • #3
      Yes I have a custom library and after your post I defenitivly need to improve it to wait ACK before the next command ;-)
      Thanks for advise, I will give you news if it solve it.