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Noise on MSP430 UART in CCS Debugger

Harvey Ku97
Prodigy 140 points
Other Parts Discussed in Thread: MSP430F5529, MSP-EXP430F5529LP, MSP-FET

Hi, 

I have a custom board with an MSP430F5529 chip that uses the UCA0TXD and UCA0RXD pins for UART communication.  The processor is programmed/debugged with an external MSP-FET430UIF programmer with CCS on a two pin JTAG (TDO/TDI and TCK).  The UART works fine when it is run standalone without an active debug session.  However, while running the debugger, the UART0RXD line becomes full of signals that looks similar to the TDO/TDI lines coming from the JTAG.  As a result, my UART communication always fails in debug mode.  

On a side note, I do not have this issue when using the MSP-EXP430F5529LP development board from TI.  Do you know what could be the issue?

Thank You

  • 0
    TI__Mastermind 49692 points

    Hi Harvey,

    In debug mode, wake-up times can be different (as discussed in Section 2.2.9.3 in the MSP430F5xx/F6xx User's Guide). For high baud rates (e.g. 115200), UART communication can be affected by this.

    Also, how are you communicating with the UART interface on the MSP430F5529? I'm asking because the MSP-FET430UIF does not support back-channel UART (as shown in Table 1 in the MSP Debuggers User's Guide). However, the MSP-FET and the eZ-FET Lite on the MSP-EXP430F5529LP do. Keep in mind that there are typically two COM ports connected: MSP Application, MSP Debug Interface

    Can you share the JTAG section of your schematic? If not, I'd recommend comparing your schematic to the MSP-EXP430F5529LP's.

    Regards,

    James

    MSP Customer Applications

  • 0 in reply to James Evans
    Prodigy 140 points

    Thank you James, it turned out that the problem was in the hardware.  The TDO/TDI was tied the enable bit on the UART device that I was interfacing with.  Thus when the debugger ran, it would toggle the UART device on/off, rendering it useless. =)

  • 0 in reply to Harvey Ku97
    TI__Mastermind 49692 points
    Very interesting! Thank you for replying with the solution to your issue.

    Regards,

    James

    MSP Customer Applications

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