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MSP430F5524: Pins not working as specified

Abhishek Veeraraghavan
Intellectual 560 points
Part Number: MSP430F5524

Pins 3.3, 3.4, which were being used for UART, have suddenly stopped working. Using them as GPIO pins is also not working. The remaining pins, functionalities appear to be working fine.

I had observed the UART not working with another board as well. I want to find out the possible reasons for this so as to take suitable precautions to avoid a recurrence of the issue. One reason for the same could be because of ESD from my body. While I don't remember touching the IC or part of the board dealing with these two pins with my bare hands there might have been inadvertent contact. 

(i) Could it be a possibility that only these two pins have been affected because of ESD because they are more sensitive than the others for some reason?

The other possibility is damage because of supplying high voltages, high currents. It is extremely unlikely that this has happened here.

Are there any other causes that you could think of for such malfunctions?

Thanks and regards

Abhishek

  • 0
    TI__Guru 60151 points

    Hello Abhishek,

    The MSP430F5524 has build in ESD protection diodes on its IO pins that can tolerate ESD discharges due to normal handling, so I wouldn't be suspicious of that at first.

    Since its only those 2 pins, what to the those pins connect to?  Another MCU?  Some other device, machinery, equipment, etc.?

    You mentioned high voltages and high currents.  Is this device used to control high voltages or high currents?

    If you don't mind saying, what is the MSP430F5524 used for?  What is the application?

  • 0 in reply to Dennis Lehman
    Intellectual 560 points

    Hi Dennis

    Thanks for your reply.

    Those pins were being used for UART. They were used to send information to another IC(board) which would drive a motor to change the focus. I have also, at times, connected them to a USB-to-UART board(FTDI232) to communicate with the MSP430 from a terminal like PuTTY. The MSP430 is being used in to communicate having multiple interfaces. Both the GPIO pins and special functions like I2C, Timers etc. The voltage driving the MSP430 is 3.3V. If you need more information, please let me know.

    Is the inbuilt ESD protection still present when not using the GPIOs but using a special function like UART?

    I would also like to take this chance to thank all the TI employees/everybody who is answering questions in the forum. More often than not questions are promptly answered and issues are resolved.

    Cheers

    Abhishek

  • 0 in reply to Abhishek Veeraraghavan
    TI__Guru 60151 points

    Hi Abishek,

    Thank you for recognizing the support that both TI and our community provides.  Its a vast amount of brain power.

    Regarding the ESD diodes, yes, they are connected to the IO pin internally so no matter if that pin is setup to be GPIO, UART, I2C, the ESD protection is there.

    Well based on your description of how much this get used or handled, especially when connected to anything that drives a motor (can never tell where back EMF can creep in and do damage) ESD might be the suspect.

    My recommendation is 2 part.

    1. (Easy - no cut's on pcb required) Add a TVS device on the RX and TX signals.  This is usually easy to do on existing PCB because you find a point where you can solder the component on the board and connected one side to the signal and the other side to ground.  Due this as close to the MSP430 as possible.

    2. (Harder - you have to cut trace on pcb) If you don't want to hunt down a TVS and maybe already have a couple of 100 ohm resistors kicking around the lab, you can cut the RX and TX signal somewhere between the MSP430 and the connector where those signals go off board and solder one resistor in the RX path and the other in the TX path.  This at least gives a little current limiting effect during the ESD event.

    Ultimately it would be best to eliminate this from happening and determine what might be causing this issue.

    Does this help?

  • 0 in reply to Dennis Lehman
    Intellectual 560 points

    Hi Dennis

    I'll discuss the issue with the manager and see what he thinks. 

    Thanks for your support.

    Cheers

    Abhishek

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