SIM808 power management - 20mA usage :(

Official Hardware Retired GSM Shield
1

Hi,

I am using SIM808 (adafruit version) with arduino pro mini 3,3V/8MHz + adxl345.

I have managed successfully to add DTR pin to wire and now I am able to successfully put SIM808 to sleep with this procedure:

void fonaSleep() {
  fona.enableGPS(false);
  digitalWrite(fonaDTR, HIGH); //dtr high
  delay (250);
  fonaSS.println("AT+CFUN = 1"); 
  fonaSS.println("AT+CSCLK = 1"); 
  if (fona.checkAwake()) Serial.println ("FONA: Awake"); else Serial.println ("FONA: Sleeping");
}

and wake up like that:

void fonaWakeUp() {
  //  Serial.println ("fona awake");
  digitalWrite(fonaDTR, LOW); //dtr low
  delay (500);
  fonaSS.println("AT + CSCLK = 0");
  fona.enableGPS(true);
  if (fona.checkAwake()) Serial.println ("TEST_IS: Awake"); else Serial.println ("TEST_IS: Sleeping");
}

and there is no problem.
I have a passive antenna.
I am putting arduino itself to sleep too.

Events that can wake up the device:

  • ADXL interrupt sent to arduino - wakes up the arduino
  • SMS / CALL / DTR low - Wake up SIM808 and generate interrupt
  • SIM808 interrupt from above point wakes up arduino

and now I am thinking...
Why do I have 20mA of power usage while sleeping - while working it's between 40-120mA.
As my system works only sometimes power usage does not concern me. But during the sleep period I would expect more like 2-5mA of usage (I even removed almost all leds).
Is there something I did wrong with my sleep process?