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MSP432E401Y: UART Connection with XBee not working

William Campbell5
Prodigy 160 points
Part Number: MSP432E401Y

Hi all,

I'm attempting to transmit between a computer and the MSP432 with UART, using two XBee Pro S3Bs for wireless communication. I'm first trying to make sure that I can actually transmit, and using the uart_echo example from the SDK. From what I can tell, the computer should transmit to its Xbee, which wirelessly transmits to the next Xbee, which transmits to the uC. Then, the uC should just send the same characters back. I have PA0, U0Rx connected to the XBee's DOUT, and PA1, U0Tx, connected to the XBee's DIN. 

Currently, the Xbee connected to the uC will receive wirelessly, a red LED will turn on for a few seconds, and then turn off. I'm assuming this is because the UART characters are going into the buffer and waiting for the uC to get them, but since the uC isn't, it just expires and the LED turns off.

edit: the red LED doesn't have anything to do with a buffer, it just turns on for a bit when data is received

If anyone has any suggestions for what to try, I'd appreciate it.

  • 0
    Guru 41995 points
    Are you sure the baud rates are the same?
  • 0 in reply to Keith Barkley
    Prodigy 160 points

    Yes, I've tried it with 115200 as well as 9600. When testing on an Arduino with the same wiring setup, 115200 introduced some noise so I changed the parameter in `MAP_UARTConfigSetExpClk` to 9600, but neither one worked. I've even monitored the UART0 registers while transmitting data and nothing changes at either baud rate.

  • 0 in reply to William Campbell5
    Guru 41995 points
    Have you checked with a scope to make sure all the signals are getting where they are supposed to go?
  • 0 in reply to Keith Barkley
    Prodigy 160 points
    I have not, but I do know with pretty high degree of certainty that the signal is getting to the MCU. We initially prototyped with an Arduino, and the XBee transmitted totally fine to it, and then totally fine back to the PC. The receiving XBee lights up an LED when it gets data, and all the wiring is the same for the Arduino and MSP432, as mentioned in my original post.
  • 0 in reply to William Campbell5
    TI__Mastermind 22580 points

    Hello William,

    As Keith has pointed out we need to understand what is not working. The UART echo examples on MSP432E4 should work as these examples are tested before releasing. I would recommend taking one step at a time (I understand it's time consuming) to have the best chance of identifying the issue.

    I have listed the steps that come to my mind. Not sure if you have already performed these steps. If you have already preformed these steps, please share the results for each step so that we can better assist you.

    • Test UART echo, running on MSP432E4, with a terminal window. Try the default baud rate first (readme of the example should have details). Both RTOS and noRTOS options available in SimpleLink MSP432E4 SDK. Pick the option that you are comfortable to modify in the future.
      • ./examples/nortos/MSP_EXP432E401Y/driverlib/uart_echo/
      • ./examples/rtos/MSP_EXP432E401Y/drivers/uartecho/
    • Once the default baud rate works, change the UART echo example to run at the desired baud rate and test with the terminal window (update terminal window settings to reflect the update baud rate in the embedded applicaiton).
    • Check if XBee is using:
      • RS232 or CMOS/TTL level. This tutorialexplains these two levels in detail.
        • If using CMOS/TTL check if XBee connector works at 3.3v. MSP432E4's UART works at 3.3v.
      • Is hardware flow control required?
        • UART echo examples in SimpleLink MSP432E4 SDK are not configured to use flow control.

    • When connecting MSP432E4 to XBee Connector, hook up a scope or logic analyzer to see if data is sent by XBee connector.

    Hope this helps!

    Regards,

    Sai

  • 0 in reply to Sai Reddy
    Prodigy 160 points
    Thank you for the steps, I'll go through those tomorrow most likely.
  • 0 in reply to William Campbell5
    Prodigy 160 points

    I went through a few of the steps you suggested, and didn't get any results, so I figured I would triple check all the actual connections. Another member of the team thought to solder the XBee to the breadboard, and turns out, it was a connection issue the whole time and we're now getting UART readings. Nonetheless, thank you for your help!

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