MAX 485

#include <SoftwareSerial.h>

#define RE 7
#define DE 6

const uint32_t TIMEOUT = 500UL;

//const byte code[]= {0x01, 0x03, 0x00, 0x1e, 0x00, 0x03, 0x65, 0xCD};
//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};

//const byte code[]= {0x01, 0x03, 0x00, 0x00, 0x00, 0x04, 0x44, 0x09};
const byte moist[] = {0x01, 0x03, 0x08, 0x02, 0x92, 0x57, 0xB6};
const byte temp[] = {0x01, 0x03, 0x08, 0xFF, 0x9B, 0x57, 0xB6};
const byte EC[] = {0x01, 0x03, 0x08, 0x03, 0xE8, 0x57, 0xB6};
const byte PH[] = {0x01, 0x03, 0x08, 0x00, 0x38, 0x57, 0xB6};

byte values[11];
SoftwareSerial mod(8, 9); // Rx pin, Tx pin

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

  delay(500);
}

void loop() {
  byte val1, val2, val3, val4;

  Serial.println("Moisture: ");
  val1 = moisture();
  Serial.println(val1);
  Serial.println(" %");
  delay(1000);

  Serial.println("Temperature: ");
  val2 = temperature();
  Serial.println(val2);
  Serial.println(" *C");
  delay(1000);

  Serial.println("Conductivity: ");
  val3 = conductivity();
  delay(1000);
  Serial.println(val3);
  Serial.println(" us/cm");

  Serial.println("Ph: ");
  val4 = ph();
  delay(1000);
  Serial.println(val4);
  Serial.println(" ph");

  delay(5000);
}

byte moisture() {
  uint32_t startTime = 0;
  uint8_t  byteCount = 0;

  digitalWrite(DE, HIGH);
  digitalWrite(RE, HIGH);
  delay(10);
  mod.write(moist, sizeof(moist));
  mod.flush();
  digitalWrite(DE, LOW);
  digitalWrite(RE, LOW);

  startTime = millis();
  while ( millis() - startTime <= TIMEOUT ) {
    if (mod.available() && byteCount<sizeof(values) ) {
      values[byteCount++] = mod.read();
      printHexByte(values[byteCount-1]);
    }
  }
  Serial.println();
  return values[4];
}

byte temperature() {
  uint32_t startTime = 0;
  uint8_t  byteCount = 0;

  digitalWrite(DE, HIGH);
  digitalWrite(RE, HIGH);
  delay(10);
  mod.write(temp, sizeof(temp));
  mod.flush();
  digitalWrite(DE, LOW);
  digitalWrite(RE, LOW);

  startTime = millis();
  while ( millis() - startTime <= TIMEOUT ) {
    if (mod.available() && byteCount<sizeof(values) ) {
      values[byteCount++] = mod.read();
      printHexByte(values[byteCount-1]);
    }
  }
  Serial.println();
  return values[4];
}

byte conductivity() {
  uint32_t startTime = 0;
  uint8_t  byteCount = 0;

  digitalWrite(DE, HIGH);
  digitalWrite(RE, HIGH);
  delay(10);
  mod.write(EC, sizeof(EC));
  mod.flush();
  digitalWrite(DE, LOW);
  digitalWrite(RE, LOW);

  startTime = millis();
  while ( millis() - startTime <= TIMEOUT ) {
    if (mod.available() && byteCount<sizeof(values) ) {
      values[byteCount++] = mod.read();
      printHexByte(values[byteCount-1]);
    }
  }
  Serial.println();
  return values[4];
}

byte ph() {
  uint32_t startTime = 0;
  uint8_t  byteCount = 0;

  digitalWrite(DE, HIGH);
  digitalWrite(RE, HIGH);
  delay(10);
  mod.write(PH, sizeof(PH));
  mod.flush();
  digitalWrite(DE, LOW);
  digitalWrite(RE, LOW);

  startTime = millis();
  while ( millis() - startTime <= TIMEOUT ) {
    if (mod.available() && byteCount<sizeof(values) ) {
      values[byteCount++] = mod.read();
      printHexByte(values[byteCount-1]);
    }
  }
  Serial.println();
  return values[4];
}

void printHexByte(byte b)
{
  Serial.print((b >> 4) & 0xF, HEX);
  Serial.print(b & 0xF, HEX);
  Serial.print(' ');
}