Serial Communication Problem

Projects Programming
1

Hi everyone, I need your help! I'm currently using serial communication with my sensor which I brought from atlas scientific , However there's some issue I faced and I need your help!

I'm using a Arduino Mega, Electrical embedded chips from Atlas Scientific , Sensor probe from there as well. I manage to code and everything is fine as I can't suspect any problem with the code, however there's no string coming out from it and I find it very weird.

Here's the following references with codes

#include <SoftwareSerial.h>
#include <stdlib.h>
#include <string.h>
#include <LiquidCrystal.h>
#define rxpin 10
#define txpin 11

SoftwareSerial myserial(rxpin,txpin);
LiquidCrystal lcd(53,51,47,45,43,41);

String inputstring = "";
String sensorstring = "";
String TDSsensorstring="";
//String Makeupstring = "";
//String Blowoffstring ="";
String phValue = "";
String Colorstring ="";

boolean input_stringcomplete = false;
boolean sensor_stringcomplete = false;
//boolean Makeup_stringcomplete = false;
//boolean Blowoff_stringcomplete = false;
boolean TDS_stringcomplete = false;
boolean Color_stringcomplete = false;

// set PWM output for respective pin
//TDS
int TDSpwm = 2;
//pH
int pHpwm = 3;
//Color
int Colorpwm = 4;
//Led
int uvLed =13;
//value 
char string_received = 0;
float ph = 0;

void setup()
{
  Serial.begin(38400);
  Serial1.begin(38400);
  Serial2.begin(38400);
  Serial3.begin(38400);
  myserial.begin(38400);
  inputstring.reserve(5);
  sensorstring.reserve(30);
  //pH
  Serial2.print("e\r");
  delay(50);
  Serial2.print("e\r");
  delay(50);
  Serial2.print("f\r");                           //call the function to change the calibration mode of the pH value
  delay(50);
  //tds
  Serial1.print("O,SG,0\r");
  delay(50);
  Serial1.print("O,S,0\r");
  delay(50);
  Serial1.print("O,TDS,0\r");
  delay(50);
  Serial1.print("O,EC,1\r");
  delay(50);
  Serial1.print("C,1\r");
  delay(50);
  pinMode(TDSpwm,OUTPUT);
  pinMode(pHpwm,OUTPUT);
  pinMode(uvLed,OUTPUT);
  pinMode(Colorpwm,OUTPUT);
  digitalWrite(uvLed,HIGH);
  lcd.begin(16, 2);
}

int PWMTDS(float x )
{
  int result = x * 0.1275 ;    // 0 - 255 is within 0 to 2000 uS/cm

  result = constrain(result,0,255);
  /*  Thus, 2.5V would open the relay and switch on the bleed off valve */
  return result;

}

int PWMPH(float x )
{
  int result = x * 21.25 ; // 0-255 is within 0 to 12 pH

  result = constrain(result,0,255);

  return result;

}
int PWMCOLOR(int x )
{
  int result = x * 0.127 ; // 0 - 255 is within from 0 to 2000

  result = constrain(result,0,255);

  return result;

}


void loop()
{
  Serial.println("");

  //tds
  while(Serial1.available())
  {
    char inchar =(char)Serial1.read();
    TDSsensorstring += inchar;
    if(inchar =='\r')
    {
      TDS_stringcomplete = true;
    }   
  }


  char carray[TDSsensorstring.length() + 1]; //determine size of the array
  TDSsensorstring.toCharArray(carray, sizeof(carray)); //put readStringinto an array
  Serial.print("TDS value :'");
  Serial.print(TDSsensorstring);
  Serial.println("'");
  char *EC=strtok(carray,",");
  float EC_float=atof(carray); 
  int value = PWMTDS(EC_float);
  Serial.print("TDS PWM Value for reference:'");
  Serial.print(value);
  Serial.println("'");
  Serial.print(EC_float);
  value = 0;
  analogWrite(TDSpwm, value);
  TDSsensorstring = "";
  delay(30);

  //LCD for TDS
  lcd.setCursor(0,0);
  lcd.print("EC:");
  lcd.setCursor(3,0);
  lcd.print(EC_float);
  lcd.setCursor(8,0);
  lcd.print("uS/cm");

  //pH Sensor
  Serial2.print("R\r");

  while(Serial2.available()){        //if we see that the pH Circuit has sent a character.
    char inchar = (char)Serial2.read();
    phValue += inchar;
    string_received=1;                //a flag used when the Arduino is controlling the pH Circuit to let us know that a complete string has been received.
  }    

  if(string_received==1){            //did we get data back from the ph Circuit?
    Serial.print("pH Value:'");
    Serial.print(phValue);
    Serial.println("'");
    char carray[phValue.length() + 1]; //determine size of the array
    phValue.toCharArray(carray, sizeof(carray)); //put readStringinto an array

      char *PH=strtok(carray,",");
    ph=atof(carray); 

    if(ph>=7.5){
      Serial.println("high\r");
    } //This is the proof that it has been converted into a float.
    if(ph<7.5){
      Serial.println("low\r");
    }   //This is the proof that it has been converted into a float.
    phValue ="";
    string_received=0;
  }             //reset the string received.

  int pHoutput = PWMPH(ph);               // set int value for the pwm
  Serial.print("Pwm ph value is : ' ");
  Serial.print(pHoutput);
  Serial.println("'");
  analogWrite(pHpwm, pHoutput); // output analog write out
  delay(30); // delay a few second to let the Hobo absorb the data
  //LCD for pH
  lcd.setCursor(0,1);
  lcd.print("pH:");
  lcd.setCursor(3,1);
  lcd.print(ph);
}

Thank you very much!

2

My guess is that this line is producing an array of size 1 which doesn't have enough room to hold any characters, just the null terminator.

  char carray[TDSsensorstring.length() + 1]; //determine size of the array

I don't think you can dynamically allocate an array that way. I think it requires a compile-time constant for the size. I'm surprised that it works at all. Perhaps the compiler is smart enough to know that the initial string length is 0.

3

I notice you have SoftwareSerial myserial(rxpin,txpin); declared as a global variable
Then you have myserial.begin(38400); within your setup

But then never mention it again. Did you have some use for it in mind?