This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

MSP430F235 Usci output level inverted

Other Parts Discussed in Thread: MSP430F235

Using Usci in Uart mode, after some time of working properly, suddenly the output levels of the UTXD0 inverted (Steady state = '0' ; Start bit = '1' and so on).

Now even after power cycle and re-setting all registers, the level remains inverted.

  • Are any external components involved on the UART lines? Have you tested the TXD pin with the other device disconnected? Can you revert back to a TI code example that still exhibits the behavior? Would it be possible to provide a screenshot of the error you are observing?

  • The same when the pin is disconnected.

    More then that, when I try to use the port (P3.4) without initiating it to Usart, but as GPIO, using debugger, the levels are also inverted !! '0' is 3V and '1' is 0V .

  • Are you evaluating on a custom board or TI-provided EVM? Have you tried using a different MSP430F235 device? Could your device have been exposed to any voltages higher than 3.6 V?

  • 1. Custom board.

    2. Different device: I have similar problem on some boards, not only one.
    I say similar because on other boards I see the line getting inverted for a period (1 miliSecond for instance) and then getting back to normal.
    Only on one board the problem persists.

    3. Higher voltage: There is RS485 invertor on the board, but the higher voltage side of it is isolated from the 3.6V.
    I have asked a H/W guy to have a second look on the schematics, but I doubt it to be the problem.

  • Given your description I'm more confident that there is a hardware issue present rather than a problem with the MSP430 devices, especially with a RS485 invertor present on the board. Can you provide any schematic or layout screenshots, particularly of the UART lines?