/* Functions for various sensor types */

float Vref  = 0; //read your Vcc voltage,typical voltage should be 5000mV(5.0V)


float microsecondsToCm(long microseconds)
{
  // The speed of sound is 340 m/s or 29 microseconds per cm.
  // The ping travels out and back, so to find the distance of the
  // object we take half of the distance travelled.
  return microseconds / 29 / 2;
}

long Ping(int pin) {
  long duration, range;

  // The PING))) is triggered by a HIGH pulse of 2 or more microseconds.
  // Give a short LOW pulse beforehand to ensure a clean HIGH pulse:
  pinMode(pin, OUTPUT);
  digitalWrite(pin, LOW);
  delayMicroseconds(2);
  digitalWrite(pin, HIGH);
  delayMicroseconds(5);
  digitalWrite(pin, LOW);

  // The same pin is used to read the signal from the PING))): a HIGH
  // pulse whose duration is the time (in microseconds) from the sending
  // of the ping to the reception of its echo off of an object.
  pinMode(pin, INPUT);
  duration = pulseIn(pin, HIGH);

  // convert the time into meters
  range = microsecondsToCm(duration);

  return (range);
}

/*read reference voltage*/
long readVref()
{
  long result;
#if defined(__AVR_ATmega168__) || defined(__AVR_ATmega328__) || defined (__AVR_ATmega328P__)
  ADMUX = _BV(REFS0) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1);
#elif defined(__AVR_ATmega32U4__) || defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__) || defined(__AVR_AT90USB1286__)
  ADMUX = _BV(REFS0) | _BV(MUX4) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1);
  ADCSRB &= ~_BV(MUX5);   // Without this the function always returns -1 on the ATmega2560 http://openenergymonitor.org/emon/node/2253#comment-11432
#elif defined (__AVR_ATtiny24__) || defined(__AVR_ATtiny44__) || defined(__AVR_ATtiny84__)
  ADMUX = _BV(MUX5) | _BV(MUX0);
#elif defined (__AVR_ATtiny25__) || defined(__AVR_ATtiny45__) || defined(__AVR_ATtiny85__)
  ADMUX = _BV(MUX3) | _BV(MUX2);
#endif
#if defined(__AVR__)
  delay(2);                                        // Wait for Vref to settle
  ADCSRA |= _BV(ADSC);                             // Convert
  while (bit_is_set(ADCSRA, ADSC));
  result = ADCL;
  result |= ADCH << 8;
  result = 1126400L / result;  //1100mV*1024 ADC steps http://openenergymonitor.org/emon/node/1186
  return result;
#elif defined(__arm__)
  return (3300);                                  //Arduino Due
#else
  return (3300);                                  //Guess that other un-supported architectures will be running a 3.3V!
#endif
}

void initCurrentSensor()
{
  Vref = readVref(); //read the reference votage(default:VCC)
}