Make battery reading more efficient

Examples/MotionMote/MotionMote.ino

@@ -51,13 +51,14 @@
 //#define FREQUENCY     RF69_868MHZ
 #define FREQUENCY     RF69_915MHZ
 #define ENCRYPTKEY    "sampleEncryptKey" //exactly the same 16 characters/bytes on all nodes!
-#define IS_RFM69HW    //uncomment only for RFM69HW! Remove/comment if you have RFM69W!
+//#define IS_RFM69HW    //uncomment only for RFM69HW! Remove/comment if you have RFM69W!
 //*********************************************************************************************
 
 #define ACK_TIME      30 // max # of ms to wait for an ack
 #define ONBOARDLED     9  // Moteinos have LEDs on D9
 #define EXTLED         5  // MotionOLEDMote has an external LED on D5
 #define BATT_MONITOR  A7  // Sense VBAT_COND signal (when powered externally should read ~3.25v/3.3v (1000-1023), when external power is cutoff it should start reading around 2.85v/3.3v * 1023 ~= 880 (ratio given by 10k+4.7K divider from VBAT_COND = 1.47 multiplier)
+#define BATT_CYCLES   30  //read and report battery voltage every this many wakeup cycles (ex 30cycles * 8sec sleep = 240sec/4min)
 #define MOTIONPIN     1 //hardware interrupt 1 (D3)
 
 //#define SERIAL_EN             //comment this out when deploying to an installed SM to save a few KB of sketch size
@@ -98,15 +99,12 @@ void motionIRQ()
   motionDetected=true;
 }
 
+byte batteryReportCycles=0;
 void loop() {
+  checkBattery();
   if (motionDetected)
   {
     digitalWrite(EXTLED, HIGH);
-    //TODO: read several samples and take average
-    //TODO: read analog only every N cycles
-    batteryVolts = analogRead(A7) * 0.00322 * 1.42;
-    dtostrf(batteryVolts, 3,2, BATstr);
-    //sprintf(sendBuf, "MOTION ............................................ BAT:%sv", BATstr);
     sprintf(sendBuf, "MOTION BAT:%sv", BATstr);
     sendLen = strlen(sendBuf);
 
@@ -114,6 +112,7 @@ void loop() {
     {
       DEBUG("MOTION ACK:OK! RSSI:");
       DEBUG(radio.RSSI);
+      batteryReportCycles = 0;
     }
     else DEBUG("MOTION ACK:NOK...");
 
@@ -121,17 +120,31 @@ void loop() {
     DEBUGln(BATstr);
 
     radio.sleep();
-    //Blink(EXTLED,50); //Blink(ONBOARDLED,3);
     motionDetected=false;
     digitalWrite(EXTLED, LOW);
   }
+  else if (batteryReportCycles == BATT_CYCLES)
+  {
+    sprintf(sendBuf, "BAT:%sv", BATstr);
+    sendLen = strlen(sendBuf);
+    radio.send(GATEWAYID, sendBuf, sendLen);
+    radio.sleep();
+    batteryReportCycles=0;
+  }
   LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF);
+  batteryReportCycles++;
 }
 
-void Blink(byte PIN, int DELAY_MS)
+byte cycleCount=BATT_CYCLES;
+void checkBattery()
 {
-  pinMode(PIN, OUTPUT);
+  if (cycleCount++ == BATT_CYCLES) //only read battery every BATT_CYCLES sleep cycles
-  digitalWrite(PIN,HIGH);
+  {
-  delay(DELAY_MS);
+    unsigned int readings=0;
-  digitalWrite(PIN,LOW);
+    for (byte i=0; i<10; i++) //take 10 samples, and average
+      readings+=analogRead(BATT_MONITOR);
+    batteryVolts = (readings / 10.0) * 0.00322 * 1.42;
+    dtostrf(batteryVolts, 3,2, BATstr); //update the BATStr which gets sent every BATT_CYCLES or along with the MOTION message
+    cycleCount = 0;
+  }
 }