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Waking from LPM4

Jake G.
Prodigy 190 points
Other Parts Discussed in Thread: MSP430F2232, MSP430F233

Hi all,

I was wondering if the external source to wake the MSP from LPM4 has to be a pinned pulled from 3V to 0V (with a push button) or if there is smaller changes that can achieve this external signal.

 

With my project we are using strain gauges to INAs that produce a voltage going from 1.5V-2.5V or if the sensor is flipped 180 degrees 1.5V to .5V.  Basically what I want is when lets say the voltage gets to 1.6 or above , or 1.4 or below the chip wakes itself up and starts running again.  Is there a way to achieve this or does it have to be a major pull (aka a push button).

 

Thanks,

Jake G.

  • 0
    Expert 1725 points

    Hi Jake,

     

    The datasheet for your device will give you an idea of the trigger thresholds for the input pins.  For example the datasheet for the MSP430F2232 has the following:

    I think that this sort of characteristic is fairly typical but check your device datasheet. 

     

    Using a simple edge trigger it would probably be difficult to get the kind of functionality that I think you want.  Perhaps consider using an external comparator to feed into one of the pins - this would give you a strong input to the MSP that would comfortably trigger the processor to wakeup.  Alternatively there are some MSPs with an inbuilt comparator (e.g. MSP430F233, '235) that you could use to trigger the wakeup event.  Another solution might be to regularly wake-up and use the ADC to sample the input and then either go back to sleep or execute a task depending upon the input level.

     

    Regards,

    Chris.

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