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UART - COM Port connection problems

Akshay Raghu
Prodigy 210 points

Hi all,

I have some questions about why my MSP430 RF2500 won't consistently connect to the COM Port for the UART connection. I coded the echo received character demo code onto my board (msp430x22x4_uscia_uart_01_9600.c), and at first it worked perfectly, exactly as I expected. I'm using RealTerm, and I changed the settings accordingly to the desired COM Port and baud rate, and the received characters were echoed back without any issues. 

However, I then coded the original Wireless Sensor Monitor Demo Access Point Code onto it, and suddenly neither RealTerm nor the WSM GUI are able to connect to the port. The WSM GUI just pops up a little window that says "unable to open com port", and when I make the same changes for Baud Rate and Port# in RealTerm, it pops up a little window that says "BadID, Probably PORT does not exist  ie_BadId - Specified comport doesn't exist.". I then tried to put just the abovementioned echo code back onto the board, but had the same issues where it couldn't connect to the COM Port.

I opened up Device Manager to check that the COM Port was connected, and indeed it is listed there, and in the properties, the Device Status window says it is working properly.

Any suggestions/ideas as to why the boards aren't connecting to my PC when they were working perfectly at first? Thanks!

  • 0
    Prodigy 10 points

    Akshay,

    The built in COM-to-USB interface is known to be cheap and buggy. Try rebooting your PC.

    -Yuri

  • 0
    Guru 227245 points

    Akshay Raghu said:
    "BadID, Probably PORT does not exist  ie_BadId - Specified comport doesn't exist."

    So the problem is on the PC side and has nothing to do with the MSP/board. THis error message shouldn't happen even if the MSP isn't in its socket at all.

    An 'unable to open COM port' often means that the port is in use by a different program. Some mouse drivers or smartphone-syncing apps are know for hijacking every newly appearing COM, lookign for their target device (some do so eternally). Especially when configured in an auto-detect mode.

    However, some programs simply have problem with accessing or finding COM ports. There are various reasons. E.g. a hole in the list (COM2 doesn't exist, but COM1, 3, 4 etc. do). Or the port number is above 4/8/16. There are at least three different ways to enumerate COM ports. Relics form DOS age and joining APIs with WinNT.

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