/* ============== Altimeter ========================
 *  Pressure is measured with the BMP180 board.
 *  Altitude will be displayed on the 4-digit display                                 
 *  
 *                                    JDu - dec 2017
====================================================

Connections for BMP180:
GND - GND
VCC - 3.3V (!!)
SDA - ANALOG pin 4
SCL - ANALOG pin 5

Connections for 4-digit TM1637 display:
GND   - GND
VCC   - 5V
CLK   - pin 6
DIO   - pin 8

Led voor negative values - Down-hill:
Pin 2

Button for reset baseline pressure:
Pin 4

==========================================================================================
*/

#include <Wire.h>  // Comes with Arduino IDE
#include <SFE_BMP180.h>
#include <TM1637Display.h>

#define CLK 6           // CLK pin for TM1637 display
#define DIO 8           // DIO pin for TM1637 display

SFE_BMP180 pressure;    // You will need to create an SFE_BMP180 object, here called "pressure":

TM1637Display display(CLK, DIO);
bool lz = false;        // Show decimal numbers with leading zeros on TM1637 display
bool col = false;       // Sets the colon indicator mode on or off
int bn = 15;            // Default brightness of the time 4-digit display

double baseline;        // baseline pressure
int TM1637pres;         // Pressure display value
int TM1637alt;          // Altimtude display value

char status;
double presMes,presSum,presAv,T,P,p0,a,t;
int led = 2;            // Led pin negative values (down-hill)
int button = 4;         // Button pin for reset Baseline
int val = LOW;
int count = 9;


void setup()
{
  Serial.begin(9600);
  
  pinMode(led, OUTPUT);
  pinMode(button, INPUT);

  uint8_t data[] = { 0xff, 0xff, 0xff, 0xff }; // Settings for the 4-digit display
  display.setBrightness(bn);                   // Brightness for display
  display.setColon(col);                       // Colon indicator on/off
    
  pressure.begin();         // initialize the sensor (it is important to get calibration values stored on the device).
  baseline = getPressure(); // Get the baseline pressure
  presSum = baseline * 9;   // For sum of 10 pressures to calculate the average value

  TM1637pres = baseline,0;
  resetBaseline();          // Display baseline pressure during startup

}


void loop(){
    
    presMes = getPressure();              // Get a new pressure reading:
    presSum = presSum + presMes;          // Sum of 10 pressures to calculate the average value
    count += 1;
    
    if (count == 10)
    {
      presAv = presSum / 10;                   // To calculate the average of the 10 pressures
      presSum = 0.0;
      count = 0;      
    }

    if (presAv <= baseline)                    // Going up-hill
      {
      a = pressure.altitude(presAv,baseline);  // The relative altitude difference between the new reading and the baseline reading
      digitalWrite(led, LOW);                  // Led is off when going up-hill so positive height
      }
      else                                     // Going down-hill
      {
      a = pressure.altitude(baseline,presAv);
      if(a>=1)digitalWrite(led, HIGH);        // Led is on when going down-hill so negative height     
      }
  
    TM1637pres = presAv,0;
    TM1637alt = a,0;

    display.showNumberDec(TM1637alt, lz);        // Display the altitude
    delay(200);

    val = digitalRead(button);
    if (val == HIGH) {
      resetBaseline();                            // Reset Baseline
  }
}

void resetBaseline()
{
  baseline = getPressure();                     // Reset the baseline pressure
  display.showNumberDec(TM1637pres, lz);        // Display the pressure on 4-dig display
  Serial.print("Reset Baseline pressure to ");  // Display the pressure on serial
  Serial.print(TM1637pres);
  Serial.println(" hPa");
  delay(2000);
}

double getPressure()
{
  char status;

  // You must first get a temperature measurement to perform a pressure reading.
  // Start a temperature measurement:
  // If request is successful, the number of ms to wait is returned.
  // If request is unsuccessful, 0 is returned.

  status = pressure.startTemperature();
  if (status != 0)
  {
    // Wait for the measurement to complete:

    delay(status);

    // Retrieve the completed temperature measurement:
    // Note that the measurement is stored in the variable T.
    // Use '&T' to provide the address of T to the function.
    // Function returns 1 if successful, 0 if failure.

    status = pressure.getTemperature(T);
    if (status != 0)
    {
      // Start a pressure measurement:
      // The parameter is the oversampling setting, from 0 to 3 (highest res, longest wait).
      // If request is successful, the number of ms to wait is returned.
      // If request is unsuccessful, 0 is returned.

      status = pressure.startPressure(3);
      if (status != 0)
      {
        // Wait for the measurement to complete:
        delay(status);

        // Retrieve the completed pressure measurement:
        // Note that the measurement is stored in the variable P.
        // Use '&P' to provide the address of P.
        // Note also that the function requires the previous temperature measurement (T).
        // (If temperature is stable, you can do one temperature measurement for a number of pressure measurements.)
        // Function returns 1 if successful, 0 if failure.

        status = pressure.getPressure(P,T);
        if (status != 0)
        {
          return(P);
        }
        else Serial.println("error retrieving pressure measurement\n");
      }
      else Serial.println("error starting pressure measurement\n");
    }
    else Serial.println("error retrieving temperature measurement\n");
  }
  else Serial.println("error starting temperature measurement\n");
}