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MSP430 launchpad as a "usb to serial/TTL" interface

Shaun Roy
Prodigy 40 points

Hi,

Is it possible to use the MSP430 launchpad as a "usb to serial/TTL" interface so that I could use the UART of some other chip/deice to communicate with the PC?
Like connecting the respective TXD nad RXD pins(of the device) to the launchpad.

If so, can anyone please elaborate?

  • 0
    Guru 227245 points

    Sure. You can simply connect any other MSPs RX and TX lines to the two RX and TX pins on the LaunchPad (don't forget to connect GDN too). However the maximum baudrate is limited to 9600Bd and you should ensure that the external MSP runs on the same voltage as the LaunchPad (3.3v?).

  • 0 in reply to Jens-Michael Gross
    Prodigy 40 points

    Ok thanks a lot. This is a great help.

    I'm aware of the 9600Bd rate limit and I'm planning to switch over to a FTDI breakout board if my application works to my expectations. But for now I'm gonna try this method.

    Just one last question, some chips run on 5v, so how do I connect them?

  • 0 in reply to Shaun Roy
    Prodigy 85 points

    Hi Shaun,

    for interfacing 5V circuits have a look at application report SLAA148.

    Regards, Max

  • 0 in reply to Max Gröning1
    Prodigy 40 points

    Thanks Max, it was the kind of article I was looking for.

    As per the article, it's possible for me to use a HCT buffer IC as an output interface for 3v-5v(Launchpad RXD to other IC). Is it possible to directly use a buffer IC(eg 74HCT367) for both the RXD and TXD launchpad pins? I could use a HCT buffer IC for the RXD (o/p) and a resistor voltage divider for the TXD(i/p), but I have a spare 74HCT367.

  • 0 in reply to Shaun Roy
    Prodigy 40 points

    I got the answer,

    (1) For 3.3v -> 5v, ie, launchpad RXD to MCU RXD,

          We may use any 7HAHCTxxx or 74HCTxxx chip as a buffer for low voltages to 5v.

    (2) For 5v -> 3.3v, i.e, MCU TXD to launchpad TXD,

          We may use any 74LVCxxx as a buffer for 5v to lower voltages.

    Other methods are also possible, besides dedicated level translation chips and buffer IC's, but I have a lot of spare 74's lying around. :)

    For more details on basic interfacing, [http://www.avrfreaks.net/index.php?name=PNphpBB2&file=viewtopic&p=612253#612253]

  • 0 in reply to Shaun Roy
    Guru 13875 points

    I'd like a little clarification on this thread -

    I'd like to use the MSP Application UART I/F on the LaunchPad like a GP TTL interface for USB - 

    how is that done?  Can I pick the signals off of the J3 header directly?  Is the BAUD rate still limited to 9600 BAUD?

    Is the only processor permitted on the other side an MSP430?  I am wondering if something equivalent to this:  http://apple.clickandbuild.com/cnb/shop/ftdichip?productID=53&op=catalogue-product_info-null&prodCategoryID=105 

    can be achieved.

    Thanks In Advance,
    John W. 

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