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MSP430FR2355: problem at power up

Diana Vertiz del Valle
Intellectual 370 points
Part Number: MSP430FR2355
Other Parts Discussed in Thread: LM1117

Hello, I have problems with the msp430fr2355. When I power up the microcontroller, if I disconnect the power source I have to wait few seconds before powering it up again,

If I power the microcontroller immediately, it doesn`t start, If I wait and power it again, it starts.

I don't have hardware reset in my board, I use reset and test pins to program the microcontroller via spy-bi-wire interface, I have 47k pull-up resistor and 1nF capacitor connected to reset. 

I use a dc power supply to power the board with 5V and have a linear regulator LM1117 fixed to 3.3V.

The microcontroller has two decoupling capacitors with 10uf and 0.1uF values and an external oscillator of 32.7680KHZ with 2 bypass capacitors of 12pF.

What could be causing this behavior? please, Help.

  • 0
    TI__Mastermind 45155 points

    Hi Diana,

    This sounds like it could stem from the power rail to the VCC pin.  Can you get a scope shot of the VCC when power is disconnected and then powered back up?  There could be something holding the voltage and this could help us determine that.

  • 0 in reply to Eddie LaCost
    Intellectual 370 points

    Hi Eddie, thanks for your answer. I don`t really get what you mean by "it could stem from the power rail to the VCC pin". 

    using the scope I don't see difference in the VCC voltage when I power back up in both cases: when the micro starts and when it doesn`t.

    These are the photos:

    power up and micro starts

    power disconnected

    power back up and micro doesn`t start

    I don't find the difference. I don't understand what could be the problem.

    thanks,

    Diana

  • 0 in reply to Diana Vertiz del Valle
    TI__Mastermind 45155 points

    Diana,

    I was referring to the power up and power down ramp.  When power is removed, does it go to 0V within a few milliseconds or does it take a long time(seconds) to ramp down?

  • 0 in reply to Eddie LaCost
    Intellectual 370 points

    Hello Eddie, thanks for your answer. Finally, my problem was in the code and had to do with the PM5CTL0 &= ~LOCKLPM5; instruction.

    I tried a simple blinking code and didn't have the problem. From there I checked different codes and got to that conclusion. 

    What I understand now is that before the instruction PM5CTL0 &= ~LOCKLPM5 I have to do all ports configurations and after the instruction

    I can for example clear interruption flags (which I had wrong). Sorry if I made you lose time with something that seemed to be hardware.

    If you have any additional information about the instruction would be really helpful. The microcontroller is working right.

    Thanks,

    Diana

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