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LAUNCHXL-F28379D: USB communication between microcontroller and PC

Dan8
Intellectual 855 points
Part Number: LAUNCHXL-F28379D

Hello,

I am using the LAUNCHXL-F28379D development board for a dc/dc converter application. I would like to collect variables/data while the converter is running and send to a PC for plotting in real time. An action which I think would be best performed using USB communication. However, I cannot find the USB pins directly on the dev board. Are these available to use?

Thanks

Dan

  • 0
    TI__Guru* 80190 points

    Dan,

    The USB connection that powers and connects the JTAG debug port is also connected to the SCIA(UART) of the F2837xD.  You should see this backchannel enumerated in your windows HW config as a UART port and you can use this to log data to the PC w/o CCS running.

    I beleive the USB pins are brought out to the micro header on the underside of the board, but I'd like to see if you are OK with the above comms before trying to pursue that.

    Best,

    Matthew

  • 0 in reply to MatthewPate
    Intellectual 855 points

    MatthewPate said:

    Dan,

    The USB connection that powers and connects the JTAG debug port is also connected to the SCIA(UART) of the F2837xD.  You should see this backchannel enumerated in your windows HW config as a UART port and you can use this to log data to the PC w/o CCS running.

    I beleive the USB pins are brought out to the micro header on the underside of the board, but I'd like to see if you are OK with the above comms before trying to pursue that.

    Best,

    Matthew

    Hi Matthew,

    My only issue with using UART is the limitation in speed which will not permit me to transfer data and plot in real-time while the converter/s is/are running. So I am trying to leave UART as the last resort. I was thinking of using Labview to plot.

  • 0 in reply to Dan8
    TI__Guru* 80190 points

    Dan,

    Thanks for the feedback, USB signals are muxed on pins GPIO42(USBDM) and GPIO43(USBDP).  These are also the same GPIOs that we are using for SCITX/RX.

    This means that the signals are brought to the isolator U5(GPIO43 on pin 11) and isolator U7(GPIO42 pin4) 

    http://dev.ti.com/tirex/explore/node?node=AKqupJcIm7HV0H1zZ5xBQA__gYkahfz__LATEST

    If you want to use these for USB, I recommend just pulling up the pin of the isolator and then wiring the USB signal from the pad to a USB header.  You can grab the USBVCC and ground from the other connector to get everything on the same plane.

    Actually, if you don't care about isolation, you could remove both U5 and U7 and populate zero ohm resistors (pads are underneath the isolators) except for the two signals you need.  That would provide a bigger pad to soldier down to.

    Best,

    Matthew

  • 0 in reply to MatthewPate
    Intellectual 855 points

    Hi Matthew,

    Thanks for the help. If the pins on the isolators are lifted up, would I loose the operation of the debugger or serial transmission?

  • 0 in reply to Dan8
    TI__Guru* 80190 points

    Dan,

    If you only lift the pins I mentioned the debug probe(XDS100) will not be impacted. 

    The back channel UART will be interrupted, but this is necessary since the isolators are uni-directional and that would impact the new USB connection you are making, as well as I'm not 100% if the FTDI chip would load those signals and not allow the USB signals to transistion correctly.  

    As I mentioned, if you don't need the isolation you could lift both ICs and just place 0ohm shunts across everything but the USB signals; perhaps have something when you don't need the USB connection you could restore the SCI/UART on demand.

    Best,
    Matthew

  • 0 in reply to MatthewPate
    Intellectual 855 points

    Thank you Matthew. I will try this.