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How to prevent sending a 0x00 from UART when the MSP430 has been reset or power on?

Sunglin Chen
Expert 2335 points
Other Parts Discussed in Thread: MSP430F2619

Dear Friends,

The UARTx of MSP430F2619 always sends out a 0x00 byte when it has been reset or power on. I want to know how to prevent it sends out this byte.  Thank you.

Sunglin. 

  • 0
    Guru 227245 points

    Sunglin Chen said:
    The UARTx of MSP430F2619 always sends out a 0x00 byte when it has been reset or power on.

    It definitely doesn't send anything by itself. However, the port pin initialization might be 'detected' by the external hardware as an erroneous start bit. In this case you should analyze the signals (with a scope) and consider adding a pullup or pulldown (depending on hardware) to suppress this when teh port goes high-impedance.

    Also, it can be possible that it happens during you initialization of the UART. maybe because you first configure the sirection bit and then switch from I/O ot UART mode or something like that. ot your ISR code jsut does that: sending an erroneous 0x00 byte when interrupts are enabled.

  • 0 in reply to Jens-Michael Gross
    Expert 2335 points

    Hi Jens-Michael,

    Thank you for your answer.  I pull-low the Rx pin of UART side of my UART-to-RS232 module. Now following your instructions, I pull-high of Rx pin and it never received 0x00 now. Thank you very much.

    Sunglin.

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