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Using Launchpad as UART <-> USB converter, baud rate?

Mikolaj Filar
Expert 1550 points
Other Parts Discussed in Thread: TUSB3410

Hi all,

I am prototyping some devices (not only with DIP MSP430). I am using MSP430 Launchpad (rev. 1.5) for an "UART debugging" (it works even on 5V, but it should break :) ).

I'm just transmit, so I don't use RXD pin.

My problem is: my transmission works only if I connect TX to pin marked green on the picture below (no jumpers used):

It allows only 9600 baud rate communication. I would like to have rating like I want. I think it uses software UART instead of hardware one. Can you explain me am I right or wrong and how to connect external TX to launchpad to have any baud rate transmission? (Of course I remember to connect Launchpad GND to transmitter GND  :) )

  • 0
    Intellectual 505 points

    Mikolaj Filar said:
    My problem is: my transmission works only if I connect TX to pin marked green on the picture below (no jumpers used):


    This is obvious from the PCB layout: in the latest version of MSP430 Launchpad that pin is connencted to the FET, not to the target MCU.

    Mikolaj Filar said:
    It allows only 9600 baud rate communication.

    You may set the communication speed to 1200 or 2400 as well... :-) Just change the settings in Windoos (or your operating system). Keep it in mind, however, that this is a software-only connenction, since tha hardware connenction is reserved for the communication between the TUSB3410 and the MSP430 MCU used in the FET.

    Regards,

    István


  • 0 in reply to Istvan Cserny
    Expert 1550 points

    Hello István,

    thank you for your answer. Unfortunately I after change baud rate in device manager I still can't obtain faster baud rate. I have tried 115 200 and 19 200. I am going to test speeds slower than 9600.

    Best regards,

    Mikolaj

  • 0 in reply to Mikolaj Filar
    Guru 92251 points

    Mikolaj Filar said:
    Unfortunately I after change baud rate in device manager I still can't obtain faster baud rate. I have tried 115 200 and 19 200. I am going to test speeds slower than 9600.

    I don't think you can change the Launchpad backchannel UART speed without changing the TUSB3410 firmware - see Bumping backchannel UART speed on MSP430 Launchpad

  • 0 in reply to Mikolaj Filar
    Intellectual 505 points

    The baudrate should be set in the application (for example Hyperterminal, putty.exe), not in the device manager.

    I suppose that we can only lower the transmission speed (i.e. 4800, 2400, 1200).

  • 0 in reply to Istvan Cserny
    Expert 1550 points

    Istvan Cserny said:
    I suppose that we can only lower the transmission speed (i.e. 4800, 2400, 1200).

    Ok, thank you for clarification.

    Best regards,

    Mikolaj

  • 0 in reply to Istvan Cserny
    Guru 227245 points

    Istvan Cserny said:
    I suppose that we can only lower the transmission speed

    Right. The 'applicaiton UART' is a software bit-banging UART inside the TUSB USB->SER converter that runa in parallel to the 'real' serial connection between debugger and FET.
    And indeed, it is limited to 9600Bd.

    However, neither DCO nor 32768Hz crystal on the G series processors allows for a reliable 115200Bd connection. Unless you implement a software FLL that synchronizes the DCO to the watch crystal (like the clock systems on 4x and 5x family do in hardware)

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