Add Low Power Capability

examples/Nano33BLESenseFirmware/LowPower.cpp

@@ -0,0 +1,35 @@
+#include "Arduino.h"
+#include "ArduinoBLE.h"
+#include "LowPower.h"
+
+#include "nrf_power.h"
+#include "nrf_uarte.h"
+#include "nrf_uart.h"
+
+void lowPower()
+{
+    // Disable UARTE0 which is initially enabled by the bootloader
+    nrf_uarte_task_trigger(NRF_UARTE0, NRF_UARTE_TASK_STOPRX); 
+    while (!nrf_uarte_event_check(NRF_UARTE0, NRF_UARTE_EVENT_RXTO)) ; 
+    NRF_UARTE0->ENABLE = 0; 
+    NRF_UART0->ENABLE = 0; 
+
+    // Enable DCDC
+    nrf_power_dcdcen_set(true);
+
+    // Turn off LED_BUILTIN
+    digitalWrite(LED_BUILTIN, LOW);
+}
+
+void lowPowerWait(unsigned long time)
+{
+    rtos::ThisThread::sleep_for(time); 
+}
+
+void lowPowerBleWait(unsigned long time)
+{
+    unsigned long timeRef = millis();
+    while (millis() - timeRef < time) {
+      BLE.poll(time - (millis() - timeRef));
+    }
+}

examples/Nano33BLESenseFirmware/LowPower.h

@@ -0,0 +1,8 @@
+#ifndef _LOWPOWER_H_
+#define _LOWPOWER_H_
+
+void lowPower();
+void lowPowerWait(unsigned long time);
+void lowPowerBleWait(unsigned long time);
+
+#endif //_LOWPOWER_H_

examples/Nano33BLESenseFirmware/Nano33BLESenseFirmware.ino

@@ -1,3 +1,4 @@
+#include "LowPower.h"
 #include <arm_math.h>
 
 #include <Arduino_APDS9960.h>
@@ -148,16 +149,14 @@ void setup() {
   BLE.addService(service);
   BLE.advertise();
 
-  digitalWrite(LED_BUILTIN, HIGH);
+  lowPower();
 }
 
 void loop() {
+  BLE.poll(1000);
   while (BLE.connected()) {
-    unsigned long now = millis();
-    if (abs((long) now - (long) lastNotify) >= 100) {
-      updateSubscribedCharacteristics();
-      lastNotify = now;
-    }
+    lowPowerBleWait(100);
+    updateSubscribedCharacteristics();
   }
 }