#include <SoftwareSerial.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128  // OLED display width, in pixels
#define SCREEN_HEIGHT 64  // OLED display height, in pixels
#define OLED_RESET -1     // Reset pin # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

#define RE 8
#define DE 7

const byte nitro[] = { 0x01, 0x03, 0x00, 0x1e, 0x00, 0x01, 0xe4, 0x0c };
const byte phos[] = { 0x01, 0x03, 0x00, 0x1f, 0x00, 0x01, 0xb5, 0xcc };
const byte pota[] = { 0x01, 0x03, 0x00, 0x20, 0x00, 0x01, 0x85, 0xc0 };

byte values[11];
SoftwareSerial mod(2, 3);

void setup() {
  Serial.begin(9600);
  mod.begin(9600);
  pinMode(RE, OUTPUT);
  pinMode(DE, OUTPUT);

  display.begin(SSD1306_SWITCHCAPVCC, 0x3C);  //initialize with the I2C addr 0x3C (128x64)
  delay(500);
  display.clearDisplay();
  display.setCursor(25, 15);
  display.setTextSize(1);
  display.setTextColor(WHITE);
  display.println(" NPK Sensor");
  display.setCursor(25, 35);
  display.setTextSize(1);
  display.print("Initializing");
  display.display();
  delay(3000);
}

void loop() {
  byte val1, val2, val3;
  val1 = nitrogen();
  delay(250);
  val2 = phosphorous();
  delay(250);
  val3 = potassium();
  delay(250);

   Serial.print("Nitrogen: ");
   Serial.print(val1);
   Serial.println(" mg/kg");
   Serial.print("Phosphorous: ");
   Serial.print(val2);
   Serial.println(" mg/kg");
   Serial.print("Potassium: ");
   Serial.print(val3);
   Serial.println(" mg/kg");
   delay(2000);
  display.clearDisplay();
  display.setCursor(0, 0);
  display.print("N: ");
  display.print(val1);
  display.print(" mg/kg"); //edit
  display.setCursor(0, 8);
  display.print("P: ");
  display.print(val2);
  display.print(" mg/kg");  //edit
  display.setCursor(0, 16);
  display.print("K: ");
  display.print(val3);
  display.print(" mg/kg");
  display.setCursor(0, 25);
  display.display();
  delay(2000);
}

byte nitrogen() {
  digitalWrite(DE, HIGH);
  digitalWrite(RE, HIGH);
  delay(10);
  if (mod.write(nitro, sizeof(nitro)) == 8) {
    digitalWrite(DE, LOW);
    digitalWrite(RE, LOW);
    for (byte i = 0; i < 7; i++) {
      values[i] = mod.read();
      Serial.print(values[i], HEX);
    }
    Serial.println();
  }
  return values[4];
}

byte phosphorous() {
  digitalWrite(DE, HIGH);
  digitalWrite(RE, HIGH);
  delay(10);
  if (mod.write(phos, sizeof(phos)) == 8) {
    digitalWrite(DE, LOW);
    digitalWrite(RE, LOW);
    for (byte i = 0; i < 7; i++) {
      values[i] = mod.read();
      Serial.print(values[i], HEX);
    }
    Serial.println();
  }
  return values[4];
}

byte potassium() {
  digitalWrite(DE, HIGH);
  digitalWrite(RE, HIGH);
  delay(10);
  if (mod.write(pota, sizeof(pota)) == 8) {
    digitalWrite(DE, LOW);
    digitalWrite(RE, LOW);
    for (byte i = 0; i < 7; i++) {
      values[i] = mod.read();
      Serial.print(values[i], HEX);
    }
    Serial.println();
  }
  return values[4];
}