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Spotty/Difficult UART Communication Through USB

TI Guy from TX
Prodigy 140 points
Other Parts Discussed in Thread: MSP430G2553

Hello all,

I am having trouble connecting to a terminal program on my PC using the UART on the MSP430G2553 Launchpad.

Now I know that in order to communicate with the PC, the jumpers on the Launchpad have to be rotated 90 degrees, as per instructions here:

Page 3, Step 6

I am running Windows 8.1 and so I use KiTTY as my terminal program. It is a PuTTY clone.

I am trying to run the RX TX demo code that can be found here. The first set CCSv5 code.

You're supposed to debug the code and then stop; connect the to the terminal program and hit the reset button on the Launchpad. It worked once, and then never again. It will never connect the first time if I unplug the Launchpad from the USB and try to reconnect.

It's not that it doesn't or never works; it's that it never connects the first time. I either have to debug, stop, hit reset on the LP numerous times in succession or I have to 'dislodge' or 'wake up' the LP using another terminal program called Terminal. I have to send data using terminal until Terminal freezes. Then I attempt to connect using KiTTY it will sometimes work.

The crazy thing is, once I get KiTTY to receive data, I am able to hit the reset button on the LP and debug like normal. The LP connects to KiTTY each time I push the reset button or push Play on the Debugger in CCS. Like normal. It will behave as intended.

But as soon as I disconnect the LP from the PC USB and reconnect, its like the PC forgets all about the LP, or forgets to communicate through UART.

I've tried:

  • Tried debugging with CCS versions 5.5 and 6.0 (currently the only one installed)
  • Un/reinstalling both versions
  • Made sure the Serial Port is visible in the Device Manager and that all port settings are the same. Tried enabling/disabling FIFO as well as different settings.
  • Tried disabling AV. I have Malwarebytes with Anti-Exploit Premium.
  • Dis/enabling and Un/renstalling the Serial Port Driver in the Device Manager in Windows

I'm not sure why its behaving this way. Sometimes I have to fiddle madly with it for about half an hour before the LP starts cooperating.

Any ideas?

Thanks in advance.

  • 0
    TI__Guru**** 212177 points

    Hello TI Guy from TX,

    First of all, not too sure why but none of your links work.  I would like to inspect the example code you are using so if you could directly send me the code file that would be great.  Please make sure that you are using a hardware UART example, where TXD and RXD pins are utilized, for which the 90 degree shift (horizontal) in the jumpers are necessary.  If you are using a software UART where pins use timers instead of UCA0 tthe jumpers should be placed vertically like the rest.

    TI Guy from TX said:

    You're supposed to debug the code and then stop; connect the to the terminal program and hit the reset button on the Launchpad. It worked once, and then never again. It will never connect the first time if I unplug the Launchpad from the USB and try to reconnect.

    I'm assuming that you are entering the debug session in order to program your G2553 device and afterwards terminate the debug session and reset the LaunchPad before beginning communication with a terminal.  If so then make sure that the serial port settings inside of your terminal are correct including baud rate, data, parity, and stop (typically 9600, 8, none, and 1, respectively).  Also try to use a USB 2.0 port as 3.0 has shown issues in the past.

    Regards,

    Ryan

  • 0 in reply to Ryan Brown1
    Prodigy 140 points

    Sorry about the links not working,not sure why they died.

    Here are the links to the software and example code I am trying to run:

    KiTTY: http://www.9bis.net/kitty/?page=Download

    Terminal: https://sites.google.com/site/terminalbpp/

    Example Code: http://longhornengineer.com/code/MSP430/UART/UART_Ver1_0.zip

    As for the port settings, they are as you suggested. I don't think its possible to communicate with the PC through the software UART, only the hardware UART. I had already rotated the jumpers 90 degrees as you suggested. I figure that out reading these instructions:  

    (Page 3, Step 6) http://www.ti.com/lit/ml/swru312b/swru312b.pdf

    I believe from the code we are using UCA0, however. Unfortunately, my PC only has USB 3.0 ports. I supposed i could see if the BIOS has a setting to drop them down back to legacy USB 2.0 but not sure if that will help.

    In any case, I found that I'm more likely to be able to connect if I hit the reset button on the LP and 'Start' in KiTTY at the same time. Not exactly an ideal work around, but I'm able to connect within a few minutes of trying instead of 30-45 minutes.

    Thanks for the help. 

  • 0 in reply to TI Guy from TX
    TI__Guru**** 212177 points

    TI Guy from TX,

    I ran your demo code on my end and it worked as is, most likely because I'm using USB 3 with Windows 7. I found a thread that also describes issues concerning using a MSP430G2 LaunchPad with Windows 8.1/USB3:
    e2e.ti.com/.../1415631

    Try to see if you can drop down to USB 2 and let me know if that changes anything.  I've learned that we are currently leading an investigation into this matter as we've seen similar issues from other users in the community.  Could you please provide your computer model and manufacturer?  This could help us further debug the issue.

    Regards,
    Ryan

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