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MSP430FR2433: Problem with UART in low-power. The clock takes too much time to stabilize frequency

Pablo Jean Rozario
Prodigy 50 points
Part Number: MSP430FR2433

Hi for everybody.

I have a problem with the MSP430FR2433. I'm implemeting a low-power product and I have noticed that in my implementation, when I set the interrupt pin, a need to wait for 200ms to send the packet.

The MSP430 enters in LPM4.5 mode, and, when wakeup, the usart peripheral is ready for receiving data after 7ms, but, the clock, needs this amount of time to stabilize.

Below, the clock generated by timer, with the SMCLK source, showing the time. The code is "stopped", and only the interrupt is working on gpio.

So, this is normal? Or there's something wrong that can cause this situation?

Thank you so much for the help.

  • 0
    TI__Guru 56685 points

    Hello Pablo,

    Are you using an external crystal by chance? Getting that stable can certainly take 200ms or much longer. Also remember when waking up from LPM4.5, you are going through a  full reset of the device. Not only that timing needs to be accounted for, but also anything about your program that happens before you are ready to use your UART interface. 

    For your application, I recommend utilizing our Compute Through Power Loss (CTPL) library in FRAM Utilities. It will allow you to save the state of the device before going into LPM4.5 mode, and when you wakeup, plug all that back into the device and start without a full re-initialization of the device. This let's ou start of fin your code exactly where you left off. Now, if you are using a external crystal and shut it off by going to LPM4.5, you would still most likely need to go through that stabilization routine again. 

  • 0 in reply to Jace H
    Prodigy 50 points

    Hello Jace, thank you for your reply.

    I'm using the REFO internal clock, sorry for forgetting about to tell this on post.

    I will try the CPTL for my application, and I will post here the results.

    Thanks :D 

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