nrf52_sleep.ino

#include <bluefruit.h>

#define WAKE_LOW_PIN  PIN_A0
#define WAKE_HIGH_PIN PIN_A1

#define SLEEPING_DELAY 10000                                // sleep after 30 seconds of blinking

void gotoSleep(unsigned long time)
{
  // shutdown when time reaches SLEEPING_DELAY ms
  if ((time>SLEEPING_DELAY))
  {
    // to reduce power consumption when sleeping, turn off all your LEDs (and other power hungry devices)
    digitalWrite(LED_BUILTIN, LOW);                     

    // setup your wake-up pins.
    pinMode(WAKE_LOW_PIN,  INPUT_PULLUP_SENSE);    // this pin (WAKE_LOW_PIN) is pulled up and wakes when externally connected to ground.
    pinMode(WAKE_HIGH_PIN, INPUT_PULLDOWN_SENSE);  // this pin (WAKE_HIGH_PIN) is pulled down and wakes when externally connected to 3.3v.
 
    // power down nrf52.
    sd_power_system_off();                              // this function puts the whole nRF52 to deep sleep (no Bluetooth)
  } 
}

// the setup function runs once when you press reset or power the board
void setup() {
  Bluefruit.begin();          // Sleep functions need the softdevice to be active.

  // initialize digital pin LED_BUILTIN as an output.
  pinMode(LED_BUILTIN, OUTPUT);
}
     
// the loop function runs over and over again forever
void loop() {
  digitalToggle(LED_BUILTIN); // turn the LED on (HIGH is the voltage level)
  gotoSleep(millis());        // call millis() and pass it to the sleep function.  On wake-up, millis will start at 0 again.
  delay(1000);                // wait for a second
}