/*
 * PID Voltage Regulator Example. 
 * 
 * See the accompaning circuit in VoltageRegulator.png. 
 * The circuit is a very poor regulator that's complex
 * and nonlinear. A good example to show PID tuning. 
 * 
 * If connected correctly the LED shows the approximate
 * output of the system. The brightness should respond
 * to the dial. Check the serial port to see what the 
 * actual system values are. 
 * 
 ********************************************************/

#include <FastPID.h>

#define PIN_INPUT     4
#define PIN_SETPOINT  5
#define PIN_OUTPUT    2
#define LED 18

float Kp=0.1, Ki=0.5, Kd=0, Hz=10;
int output_bits = 8;
bool output_signed = false;

FastPID myPID(Kp, Ki, Kd, Hz, output_bits, output_signed);

const int    SAMPLE_NUMBER      = 10;
const double BALANCE_RESISTOR   = 9880.0;
const double MAX_ADC            = 4095.0;
const double BETA               = 3974.0;
const double ROOM_TEMP          = 298.15;
const double RESISTOR_ROOM_TEMP = 10000.0;
double       currentTemperature = 0;

void setup()
{
  Serial.begin(9600);
  pinMode(PIN_INPUT, INPUT);      //Feedback sensor
  pinMode(PIN_OUTPUT, OUTPUT);    //PWM atuator
  pinMode(PIN_SETPOINT, INPUT);   //Input setpoint
}

void loop()
{
  digitalWrite( LED, ( millis() % 1000 ) < 50 );

  int setpoint = 300; 
  int feedback = 10 * pSENSOR();    //Converte a leitura do sensor para inteiro

  uint32_t before, after;
  before = micros();
  uint8_t output = myPID.step(setpoint, feedback);
  after = micros();
  
  analogWrite(PIN_OUTPUT, output);
  Serial.print(" Set: "); 
  Serial.print(setpoint); 
  Serial.print(" Sensor: "); 
  Serial.print(feedback);
  Serial.print(" PWM: ");
  Serial.println(output);
  delay(100);
}

double pSENSOR() 
{
  double rThermistor = 0;            // Holds thermistor resistance value
  double tKelvin     = 0;            // Holds calculated temperature
  double tCelsius    = 0;            // Hold temperature in celsius
  double adcAverage  = 0;            // Holds the average voltage measurement
  int    adcSamples[SAMPLE_NUMBER];  // Array to hold each voltage measurement
  
  for (int i = 0; i < SAMPLE_NUMBER; i++  ) { adcSamples[i] = analogRead(PIN_INPUT); delay(10); }
  for (int i = 0; i < SAMPLE_NUMBER; i++  ) { adcAverage  = adcSamples[i]; }

  adcAverage /= SAMPLE_NUMBER;
  rThermistor = BALANCE_RESISTOR * ( (MAX_ADC / adcAverage) - 1);
  tKelvin = (BETA * ROOM_TEMP) / (BETA + (ROOM_TEMP * log(rThermistor / RESISTOR_ROOM_TEMP)));
  tCelsius = tKelvin - 273.15;  // convert kelvin to celsius
  tCelsius = tCelsius * (-1);   //Por algum motivo é necessário tornar a tCelsius positivo

  return tCelsius;    // Return the temperature in Celsius
}