Hello guys, first time here! I hope you could help me with an issue about an NPK sensor I'm working with for my degree's final project.
This is the code from this tutorial that I'm using but I keep getting the same 255 answer for all three parameters:
#include <SoftwareSerial.h>
#include <Wire.h>
// RE and DE Pins set the RS485 module
// to Receiver or Transmitter mode
#define RE 8
#define DE 7
// Modbus RTU requests for reading NPK values
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};
// A variable used to store NPK values
byte values[11];
// Sets up a new SoftwareSerial object
// Digital pins 10 and 11 should be used with a Mega or Mega 2560
SoftwareSerial mod(2, 3);
//SoftwareSerial mod(10, 11);
void setup() {
// Set the baud rate for the Serial port
Serial.begin(9600);
// Set the baud rate for the SerialSoftware object
mod.begin(9600);
// Define pin modes for RE and DE
pinMode(RE, OUTPUT);
pinMode(DE, OUTPUT);
delay(500);
}
void loop() {
// Read values
byte val1,val2,val3;
val1 = nitrogen();
delay(250);
val2 = phosphorous();
delay(250);
val3 = potassium();
delay(250);
// Print values to the serial monitor
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);
}
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++){
//Serial.print(mod.read(),HEX);
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++){
//Serial.print(mod.read(),HEX);
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++){
//Serial.print(mod.read(),HEX);
values[i] = mod.read();
Serial.print(values[i],HEX);
}
Serial.println();
}
return values[4];
}
I'm also using a MAX RS485 module to connect it to my arduino uno R4 wifi.
Also, as I'm a new user I'm not allowed to upload files so I'll post the datasheets download link over here. I've also checked the wiring several times and I'm perfectly sure that it's fine.
The datasheet mentions that the power supply must be between 4.5V and 30V, so I've conected the arduino's V_in to the power supply of both the sensor and the MAX RS485 module.
I've already seen quite a few posts about this kind of sensors but I have not been able to solve this issue.
since you posted the code exactly as requested in the How to get the most out of... post, and linking to the datasheet.
