arduino snippet to make a gps/ble speedometer controlled by ios app

arduino-speedometer.ino

/*
  MTB Speedometer 1.0
  - GPS module
  - BLE 4 module
  - 7 Segment display
  - DHT sensor for temperature and humidity
  (c) 2017 Alberto Pasca
*/

#include <string.h>
#include <ctype.h>

// Adafruit 7 segment
#include <Adafruit_GFX.h>
#include "Adafruit_Sensor.h"
#include "Adafruit_LEDBackpack.h"

// GPS
#include "TinyGPS++.h"

// Bluetooth
#include <SoftwareSerial.h>

// Humidity & Temperature
#include "DHT.h"

// -----------------------------------------------------------------------------

int byteGPS =- 1;

int gpsPinRX = 0;
int gpsPinTX = 1;
int btPinRX  = 10;
int btPinTX  = 11;

// TinyGPS
TinyGPSPlus gps;

// 7 Segment
Adafruit_7segment matrix = Adafruit_7segment();
// CLK => A5
// DAT => A4

// Bluetooth
SoftwareSerial BTSerial(btPinRX, btPinTX); // Receive (RD), Transmit (TxD)

// DHT sensor
#define DHTPIN 2
#define DHTTYPE DHT22
DHT dht(DHTPIN, DHTTYPE);

char btReceivedData = 'A';

// -----------------------------------------------------------------------------

struct GPSData {
  double lat;
  double lon;
  double alt;
  double kmh;
  int date;
  int time;
};

struct DHTData {
  double temp;
  double hum;
};

GPSData *gpsData = new GPSData();
DHTData *dhtData = new DHTData();

// -----------------------------------------------------------------------------

void setup() {
  pinMode(gpsPinRX, INPUT);
  pinMode(gpsPinTX, OUTPUT);

  Serial.begin(4800);

  // init display
  matrix.begin(0x70);

  // init serial bt
  BTSerial.begin(9600);

  // init dht sensor
  dht.begin();
}

void loop() {

  prepareGPSData( gpsData );

  float temp = dht.readTemperature();
  float hum  = dht.readHumidity();
  if ( temp > 0 ) {
    dhtData->temp = temp;
  }
  if ( hum > 0 ) {
    dhtData->hum  = dht.readHumidity();
  }

  if ( btReceivedData == 'A' ) {
    writeOnDisplay( gpsData->kmh );
  } else if ( btReceivedData == 'B' ) {
    writeOnDisplay( gpsData->lat );
  } else if ( btReceivedData == 'C' ) {
    writeOnDisplay( dhtData->temp );
  } else if ( btReceivedData == 'D' ) {
    writeOnDisplay( dhtData->hum );
  }

  BTSerial.write( prepareBTData(gpsData, dhtData) );

  char currentData = readBluetoothCommand();
  if ( currentData == 'A' || currentData == 'B' || currentData == 'C' || currentData == 'D' ) {
    btReceivedData = currentData;
  }

  delay(100);
}


// -----------------------------------------------------------------------------


char* prepareBTData( GPSData *gps, DHTData *dht ) {

  String btOutputStr = String(gps->lat);
  btOutputStr += "§";
  btOutputStr += String(gps->lon);
  btOutputStr += "§";
  btOutputStr += String(gps->alt);
  btOutputStr += "§";
  btOutputStr += String(gps->kmh);
  btOutputStr += "§";
  btOutputStr += String(gps->date);
  btOutputStr += "§";
  btOutputStr += String(gps->time);
  btOutputStr += "§";
  btOutputStr += String(dht->temp);
  btOutputStr += "§";
  btOutputStr += String(dht->hum);
  btOutputStr += "#";

  char btOutput[btOutputStr.length() * 2];
  btOutputStr.toCharArray(btOutput, btOutputStr.length() * 2);
  Serial.println( btOutput );
  return btOutput;

}

char readBluetoothCommand() {
  return BTSerial.read();
}

void writeOnDisplay( double text ) {

  matrix.println( text );
  matrix.writeDisplay();

}

void prepareGPSData( GPSData *data ) {

  // gps
  byteGPS = Serial.read();          // Read a byte of the serial port
  if ( byteGPS != -1 ) {
    // TinyGPS
    gps.encode( Serial.read() );

    data->lat  = gps.location.lat();
    data->lon  = gps.location.lng();
    data->alt  = gps.altitude.meters();
    data->kmh  = gps.speed.kmph();
    data->time = gps.time.value();
    data->date = gps.date.value();
  }

  delay(100);

}


// -----------------------------------------------------------------------------