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Backchannel UART Flow Control MSP432

Federico Favaro1
Prodigy 180 points

Hello,

I'm having problems to use flow control on the backchannel UART from MSP432 Launchpad. Basically, I keep RTS signal from the MCU high and send some bytes from the PC. The data arrives to the MCU ignoring the state of RTS signal. From the PC (windows) I'm using Realterm software. I have connected the jumpers accordingly and also verified that RTS signal goes high with an oscilloscope.

Why is this not working?

Best regards,

Federico

  • 0
    Guru 11940 points
    Are you sure that your MSP432 Launchpad application is actually using flow control ?
    With RS232-like protocols (UART), you need to make sure that both endpoints use the same configuration, else communication fails.
  • 0 in reply to f. m.
    Prodigy 180 points
    In my application, data flows only one way, from the PC to the MCU. For that reason, I am only driving Rts pin from the MCU, to control the flow comming from the PC. Cts pin from the MCU is configured as an input with a pull down. Is there something I am misssing? The state (high) of Rts pin is not enough to stop the Tx from the PC?
  • 0 in reply to Federico Favaro1
    Guru 11940 points
    Not sure if I understood this correctly, but the PC side needs to be configured to hardware flow control as well.
    And there are exist cables having only 3 wires (Tx, Rx, Gnd). You need to confirm signals at the intended "target" (signal receiver), not only at the source (MCU pin).
  • 0 in reply to f. m.
    Prodigy 180 points

    I have configured the PC to use hardware flow control (RTS/CTS in Realterm config) but I'm not able to confirm the signals from the PC side since they are "converted to USB" by the XDS110-ET Emulator in the Launchpad. The XDS110-ET is the one who receives RTS signal from MCU and I have no idea what he sends to the PC.

  • 0 in reply to Federico Favaro1
    Guru 11940 points

    I'm not really familiar with this XDS100 emulator - mostly using other Cortex M boards like the TM4C launchpad and competitor products.

    But it sounds like you are using a VCP (virtual COM port) provided by this debug adapter. You might need to check if it actually supports hardware flow control. I know of others (on different evaluation boards) who do not - the RTS/CTS lines from the MCU's UART to the JTAG/VCP adapter are already missing.

  • 0
    Prodigy 180 points

    I'm still unable to make this work. Is there someone with experience in XDS100 emulators and flow control who can answer this question?

    Regards,

    Federico

  • 0 in reply to Federico Favaro1
    Guru 11940 points

    Perhaps this thread can be helpful, provide you further information.

  • 0 in reply to Federico Favaro1
    TI__Mastermind 25045 points

    Hola Federico,

    Let me look into this and I'll get back to you with some example code. Hopefully tomorrow.
     
    Thanks,

    David

  • 0 in reply to DavidL
    Prodigy 180 points

    Hola David,

    Thank you for your answer! I will await your response.

    Regards,

    Federico

  • 0 in reply to DavidL
    Prodigy 180 points

    David, any news regarding this topic?

    Regards,

    Federico

  • 0 in reply to Federico Favaro1
    TI__Mastermind 25045 points
    Hola Federico,

    It took me a little bit longer than expected and I do not have good news. I just confirmed that the flow control is not supported as part of the LP onboard XDS110.

    We will update the LP User's Guide to reflect these changes.

    Regards,

    David
  • 0 in reply to DavidL
    Prodigy 180 points
    That's a shame. Thank you very much for your support anyway.

    Regards,
    Federico

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