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RST pin not working

Cesar Triana
Prodigy 60 points
Other Parts Discussed in Thread: MSP430F5510, LM26003

Hi,

I'm new to this forum and MSP430 programming. I'm building a simple circuit using a MSP430F5510 which should output a single PWM signal, no big deal. The programming works just fine since I've seen it working. The problem is that the microcontroller not always starts up, even though the required voltage is fed to it.

I'm using a TI LM26003 as a 3,3V regulator for the MCU, but I don't think that is the problem since the output voltage is always 3,3V and is always fed to the MCU. So I'm kind of guessing the problem might be the MCU not properly resetting/starting up.

I checked the voltage on the MCU RST pin, and it is always HIGH. Should it behave like that? I've got the RST pin connected to the corresponding JTAG connector pin (JTAG communication does work fine), and to a push button in series with a 10k resistor connected to 3,3V. But like I said, the pin is always HIGH even though the push button is not pressed (it is not a normally closed button). I read online that you're supposed to drive the RST pin LOW to resert the MCU instead of driving it HIGH as my circuit does, but this part of the circuit I got it from a colleague and in his circuit it works fine. Maybe the RST pin usage has to be software configured for the push button to be able to reset it? Or could it be that something's wrong with my MCU? (Which I doubt since it does work from time to time).

Thanks in advance for your help,

Best Regards.

  • 0
    Guru 34483 points

    And what about PUR pin? Is it connected to ground? Maybe with floating PUR pin, after reset device is entering to USB BSL mode.


    If PUR pin is grounded, and problem is related to RESET (BTW, MSP430F5510 device have internal pullup on RESET pin), you can add 1n - 2.2 nF cap / 47 k resistor combination like on TI MSP430F5xx boards.

  • 0 in reply to zrno soli
    Prodigy 60 points

    PUR is not grounded, it is connected to a voltage divider for using the USB.

  • 0
    Prodigy 60 points

    I changed the values of the capacitors for the 4MHz crystal on the board and it got better, but not quite right. It now turns on every time as long as I connect it to voltage fast enough from a previous disconnection, i.e. the first time it doesn't turn on, but the subsequent times it does as long as I connect it fast enough. If i disconnect it and connect it once again within ~1 second, it does turn on. Longer than that it doesn't. I played with the capacitor values but I still can't get it to work every time. So I'm not quite sure if that's the main problem with the circuit.

  • 0 in reply to Cesar Triana
    Intellectual 540 points
    Have you checked the switching regulator to see if the proper support component values are being used for your load?

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