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I was reading the Family guide, as well as the F5529 guide and could not really determine how power consumption is affected by the UART in Asynch mode.  I expect that baud will certainly play a role, as the core voltage must be increased to run at higher frequencies.

The thought behind all of this is driven by wanting to keep battery life at a maximum, of course...

My GPS/Iridium Satellite comm device is following this basic flow:

loop()

switch(currentState)

case ENABLE_GPS:

{

  Serial1.begin(9600);

  digitalWrite(GPS_SleepPin, HIGH); //enable the GPS

  currentState = WAIT_FOR_GPS_FIX;

  break;

}

case WAIT_FOR_GPS_FIX:

{

  if(bGPS_sentences_valid)

    {

       currentState = DISABLE_GPS;

    }

  break;

}

case DISABLE_GPS:

{

  Serial1.end();

  digitalWrite(GPS_SleepPin, LOW); //disable the GPS

  currentState = SLEEP;

  break;

}

case SLEEP:

{

  sleepSecond(3600); //wait an hour for next fix

  currentState = ENABLE_GPS

  break;

}

default:

  break;

}

 

Is there a power-saving benefit to stopping and starting the UART? I would assume so, but am aware that the UART code has a built-in sleep() as well.

 

As an aside:  I was seeing all kinds of weird behavior when trying to use the enable pin on the GPS, an MT3339.  I finally tracked it down to the fact that when the P6_5 pin went LOW, the Enable pin on hte MT3339 drew 350uA...  a 10K resistor has resolved that problem, but the ee noob that I am, it took me some time to find the problem. Whle the boards that arrived on Saturday don't have a resistor in the circuit, in the future I'll probably add both a mosfet for the pin to drive, AND a resistor to limit the loss of precious electrons...

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