UART communication issue between ARM A9 and STM32

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UART communication issue between ARM A9 and STM32

Contributor III


    I am trying to make a firmware update for a STM32 uC from ARM Cortex A9. When i send 1 byte command everything is Ok and I get response on UART. But for two bytes commands I see that the ARM puts only 1 byte on the line and ends it with low bit(start bit) instead of high bit(stop bit). 

    I have attached the picoscope output for both cases(when sending 1 bte or 2 bytes to STM32).

    What should I check on ARM side for UART inconsistencies with STM32.

    I know that the STM32 expects even parity and 8 bit data.

    I have set on ARM side 8 bit data/even parity/1 stop bit. I have also tried with 9 bit data as I read that STM32 interprets parity bit as the last bit.

    When I am using parity none, the ARM puts both bytes on TX line but then I don't get a response from STM32 anyway as it probable expects parity even?

    What could I investigate further on ARM side?



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