GasMeter

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/*
 * Demo program for the non-blocking: 
 * 
 * gas_Meter_Reader(float gasMeter, int interval)
 *
 * Reads an analog pulse from a reflection sensor on an input. Adds 0,1 M3 to gasMeter per pulse
 * Interval sets the time betweet readings, should be set to about 500 ms for the Makerspace meter
 * Tested on a ESP8266 but should run on almost anything
 * 
 * Aart 03-2017 V 0.2
 */

#define SENSOR_PIN A0           // Gas meter reflection sensor pin (analog)
#define DETECT 500              // Analog value "definately a mirror"
#define RELEASE 700             // Analog value "definately no mirror"
#define INTERVAL 500            // Time between readings in ms 

#define LOAD_PIN 2              // PWM output for CPU load. 2 = onboard led on the Wemos D1. High = no load = led off
#define SEND_INTERVAL 2000      // Time between output messages in ms
// #define debug_gas            // gasmeter routine debug messages

void setup() {
  Serial.begin(115200);
  delay(10);
  Serial.println(F("Hello. This is the gasMeter Non blocking routine demo"));
  
  pinMode(LOAD_PIN, OUTPUT);
  digitalWrite (LOAD_PIN,LOW); 
}


void loop() {
  static float gasMeter;    // current value of gas meter
  static long start_time;   // ms. Start time of last 100 ms system tick
  static long last_send;    // ms. Time since last message

  gasMeter = gas_Meter_Reader(gasMeter, INTERVAL); // The actual function is called

  if (millis() < last_send) last_send = millis(); // Roll over
  if ((millis() - last_send) > SEND_INTERVAL) { // once in a while.. 
    last_send = millis(); 
    Serial.print("gasMeter: ");
    Serial.println(gasMeter);
  }

  // Wait up to 100 ms in this idle & load measurement routine
  digitalWrite (LOAD_PIN,HIGH);   
  if (millis () < start_time) start_time = millis(); // roll over
  while (millis() - start_time  < 100) {
    delay(1); // Do nosePicking();  
  }
  digitalWrite (LOAD_PIN,LOW); 
  start_time = millis(); 
}

float gas_Meter_Reader(float gasMeter, int interval) { 
  /*
   * Reading the input and adding 0.1 m3 per detected pulse. 
   * Non-blocking
   */
  static long last_run;    // Time of last run of this routine in ms
  int sensor;   // sensor value
  enum states { // States of the input state machine 
    wait_for_start,
    doublecheck,
    count, 
    wait_for_end, 
  };
  static int state = wait_for_start;  

  if (millis() < last_run) last_run = millis();  // roll over
  if (millis() - last_run < interval) return gasMeter; 
  last_run = millis(); // Run once every 500 ms
  
  sensor = analogRead(SENSOR_PIN); 
  
  #ifdef debug_gas 
  Serial.print ("Sensor: "); 
  Serial.println (sensor); 
  #endif  
  
  switch (state) { 
    case wait_for_start: { 
      if (sensor < DETECT) state = doublecheck; 
      #ifdef debug_gas
        Serial.println("State: Wait for start"); 
      #endif
    } break; 
    
    case doublecheck: { 
      if (sensor < DETECT) state = count; 
      if (sensor > DETECT) state = wait_for_start;  
      #ifdef debug_gas
        Serial.println("State: Doublecheck"); 
      #endif
    } break; 
    
    case count: { 
      gasMeter += 0.1;  // 0,1 m3 per omwenteling
      #ifdef debug_gas
        Serial.print("State: count; gasMeterValue: "); 
        Serial.println(gasMeter); 
      #endif
      state = wait_for_end; 
    } break; 
    
    case wait_for_end: { 
      if (sensor > RELEASE) state = wait_for_start; 
      #ifdef debug_gas
        Serial.println("State: Wait for end"); 
      #endif
    } break; 
    break; 
  }
  return gasMeter; 
}