here is my code
#include <SoftwareSerial.h>
#include <Wire.h>
#define RE 8
#define DE 7
// The following are the Inquiry frames which are send to the NPK sensor
//for reading the Nitrogen, Phosphorus, and Potassium values
// We defined three arrays with names nitro_inquiry_frame, phos_inquiry_frame, and pota_inquiry_frame
// Each inquiry frame have 8 values
const byte nitro_inquiry_frame[] = {0x01,0x03, 0x00, 0x1e, 0x00, 0x01, 0xe4, 0x0c};
const byte phos_inquiry_frame[] = {0x01,0x03, 0x00, 0x1f, 0x00, 0x01, 0xb5, 0xcc};
const byte pota_inquiry_frame[] = {0x01,0x03, 0x00, 0x20, 0x00, 0x01, 0x85, 0xc0};
byte values[11];
SoftwareSerial modbus(2,3);
void setup() {
Serial.begin(9600);
modbus.begin(9600);
pinMode(RE, OUTPUT);
pinMode(DE, OUTPUT);
delay(1000);
}
void loop() {
// we will need three variables of the type byte to store the values of
// Nitrogen, phosphorus, and Potassium.
byte nitrogen_val,phosphorus_val,potassium_val;
nitrogen_val = nitrogen();
delay(2500);
phosphorus_val = phosphorous();
delay(2500);
potassium_val = potassium();
delay(2500);
Serial.print("Nitrogen_Val: ");
Serial.print(nitrogen_val);
Serial.println(" mg/kg");
Serial.print("Phosphorous_Val: ");
Serial.print(phosphorus_val);
Serial.println(" mg/kg");
Serial.print("Potassium_Val: ");
Serial.print(potassium_val);
Serial.println(" mg/kg");
delay(1000);
}
/*
* Now, we will need to create three user-defined functions to read the Nitrogen, Phosphorus, and Potassium values
* These user-defined functions are going to be of the type byte
*/
byte nitrogen(){
digitalWrite(DE,HIGH);
digitalWrite(RE,HIGH);
delay(10);
if(modbus.write(nitro_inquiry_frame,sizeof(nitro_inquiry_frame))==8){
digitalWrite(DE,LOW);
digitalWrite(RE,LOW);
// When we send the inquiry frame to the NPK sensor, then it replies with the response frame
// now we will read the response frame, and store the values in the values[] arrary, we will be using a for loop.
for(byte i=0;i<7;i++){
//Serial.print(modbus.read(),HEX);
values[i] = modbus.read();
// Serial.print(values[i],HEX);
}
Serial.println();
}
return values[4]; // returns the Nigtrogen value only, which is stored at location 4 in the array
}
byte phosphorous(){
digitalWrite(DE,HIGH);
digitalWrite(RE,HIGH);
delay(10);
if(modbus.write(phos_inquiry_frame,sizeof(phos_inquiry_frame))==8){
digitalWrite(DE,LOW);
digitalWrite(RE,LOW);
for(byte i=0;i<7;i++){
//Serial.print(modbus.read(),HEX);
values[i] = modbus.read();
// Serial.print(values[i],HEX);
}
Serial.println();
}
return values[4];
}
byte potassium(){
digitalWrite(DE,HIGH);
digitalWrite(RE,HIGH);
delay(10);
if(modbus.write(pota_inquiry_frame,sizeof(pota_inquiry_frame))==8){
digitalWrite(DE,LOW);
digitalWrite(RE,LOW);
for(byte i=0;i<7;i++){
//Serial.print(modbus.read(),HEX);
values[i] = modbus.read();
//Serial.print(values[i],HEX);
}
Serial.println();
}
return values[4];
}
