intrepidkarthi · February 7, 2017 19:36 · May 13, 2014 · May 11, 2014 · May 11, 2014
diff --git a/people-counter-v1.ino b/people-counter-v1.ino
@@ -20,7 +20,6 @@ int numberOfPingsObsevedHumanIsInRange = 0;
 // minimum count of hitting a "person" by ultrasonic sensor to accept it as a person
 static int minPingCountToAcceptHuman = 2;
 
-static int sleepBetweenTwoHumansInMillis = 300;
 static float maxBlackoutInMillis = 500;
 static int iSeeHumanThresholdInCm = 250;
 

diff --git a/people-counter-v1.ino b/people-counter-v1.ino
@@ -24,6 +24,7 @@ static int sleepBetweenTwoHumansInMillis = 300;
 static float maxBlackoutInMillis = 500;
 static int iSeeHumanThresholdInCm = 250;
 
+// set to true to make the LED blink everytime we count a person
 const boolean DEBUG = true;
 
 void setup() {

diff --git a/people-counter-v1.ino b/people-counter-v1.ino
@@ -0,0 +1,182 @@
+#include <lowpower.h>
+#include <EEPROM.h>
+
+int currentSessionId;
+int humanCount = 0;
+int eepromHumanCount = 0;
+long eepromLastSyncAt = 0;
+
+const int trigPin = 9;
+const int echoPin = 10;
+const int humanCountedLedPin = 11;
+
+boolean iSeeHuman = false;
+boolean iTrackHuman = false;
+long lastTimeISawHuman;
+
+// once we observe a person, we count number of times the person stays in front of our device
+int numberOfPingsObsevedHumanIsInRange = 0;
+
+// minimum count of hitting a "person" by ultrasonic sensor to accept it as a person
+static int minPingCountToAcceptHuman = 2;
+
+static int sleepBetweenTwoHumansInMillis = 300;
+static float maxBlackoutInMillis = 500;
+static int iSeeHumanThresholdInCm = 250;
+
+const boolean DEBUG = true;
+
+void setup() {
+  LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF);  
+  pinMode(trigPin, OUTPUT);
+  pinMode(echoPin, INPUT);
+
+  detectCurrentSessionId();
+
+  if(DEBUG){
+    pinMode(humanCountedLedPin, OUTPUT);
+    blinkHumanCountedLed();
+
+
+    Serial.begin(9600);
+    delay(500);
+    printHistory();
+  }
+}
+
+
+void loop()
+{
+  iSeeHuman = pingDistanceInCm() < iSeeHumanThresholdInCm;
+
+  if(iSeeHuman && !iTrackHuman) // we have first contact with human
+  {
+    numberOfPingsObsevedHumanIsInRange = 1;
+    iTrackHuman = true;
+    lastTimeISawHuman = millis();
+  } 
+  else if(iSeeHuman && iTrackHuman)  // we already recognized him and we keep tracking him
+  {
+    numberOfPingsObsevedHumanIsInRange++;
+    lastTimeISawHuman = millis();
+  } 
+  else if(!iSeeHuman && iTrackHuman) 
+  {
+    if((millis() - lastTimeISawHuman) < maxBlackoutInMillis)
+    {      
+      // wo dont see him now, but we believe he may still be in sight
+    }
+    else 
+    { // we havent seen him for too long
+      iTrackHuman = false;
+
+      if(numberOfPingsObsevedHumanIsInRange >= minPingCountToAcceptHuman){
+        humanCount++;
+        if(DEBUG)
+          blinkHumanCountedLed();
+
+        }
+      }
+    } 
+  else  
+  {
+    // !iSeeHuman && !iTrackHuman - nothing to do
+  }
+
+  syncHumanCount();
+  LowPower.powerDown(SLEEP_15Ms, ADC_OFF, BOD_OFF);    
+}
+
+long pingDistanceInCm(){
+  digitalWrite(trigPin, LOW);
+  delayMicroseconds(2);
+  digitalWrite(trigPin, HIGH);
+  delayMicroseconds(10);
+  digitalWrite(trigPin, LOW);
+
+  long durationInMicroseconds = pulseIn(echoPin, HIGH, 15 * 1000); 
+
+  long cm  = durationInMicroseconds / 58;
+  if(cm == 0){
+    // when the background is too far away, the measurement may return distance = 0 cm
+    // in such case we want to avoid counting this ping as a human presence
+    cm = 500; 
+  }
+
+  return(cm);
+}
+
+void detectCurrentSessionId(){
+  int previousSessionId = EEPROM.read(0);
+  if(previousSessionId == 255) // "Locations that have never been written to have the value of 255."
+    currentSessionId = 1;
+  else
+    currentSessionId = previousSessionId + 1;
+
+  EEPROM.write(0, currentSessionId);
+}
+
+int majorHumanCount;
+int minorHumanCount;
+int majorBytePosition;
+int minorBytePosition;
+
+// we dont want to write too ofter to eeprom:
+// atmel warns the eeprom may die after 100.000 r&w cycles (per single eeprom byte)
+// also the 1byte write takes cca 3.3ms
+
+void syncHumanCount()
+{ 
+  if((humanCount - eepromHumanCount) > 10){ 
+    majorHumanCount = humanCount / 256;
+    minorHumanCount = humanCount % 256;
+
+    majorBytePosition = currentSessionId * 2 - 1;
+    minorBytePosition = majorBytePosition + 1;   
+
+    EEPROM.write(majorBytePosition, majorHumanCount);
+    EEPROM.write(minorBytePosition, minorHumanCount);
+
+    eepromLastSyncAt = millis();
+    eepromHumanCount = humanCount;
+
+  }
+}
+
+// session 1: 1,2
+// session 2: 3,4
+// session 3: 3*2 -1, 3*2
+// session 100: [100*2 - 1, 100*2]
+
+// majorBytePosition = sessionId*2 - 1
+// minorBytePosition = sessionId*2
+void printHistory()
+{
+  Serial.write("History\n\n");
+
+  int sessionHumanCount;
+  for(int sessionId = 1; sessionId < currentSessionId; sessionId++)
+  {
+    majorBytePosition = sessionId * 2 - 1;
+    minorBytePosition = majorBytePosition + 1;
+    sessionHumanCount = 256 * ( EEPROM.read(majorBytePosition)) + EEPROM.read(minorBytePosition);
+    Serial.print("session id: ");
+    Serial.println(sessionId);
+    Serial.print("session count: ");
+    Serial.println(sessionHumanCount);
+    Serial.println();   
+  }
+}
+
+void resetSessionInfoInEeprom(){
+  EEPROM.write(0, 0);
+}
+
+void blinkHumanCountedLed(){
+  for(int i = 0; i < 5; i++){
+    digitalWrite(humanCountedLedPin, HIGH);
+    delay(50);
+    digitalWrite(humanCountedLedPin, LOW);
+    delay(50);
+  }
+}
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