Código para Arduino atuando como transmissor Sistema de Olfato Artificial

//Serial communication between ARDUINO and/or node MCU - Program of Master

//    RODRIGUEZ-GAMBOA, JUAN C. & ALBARRACIN-ESTRADA, E. SUSANA     
//    - E-MAIL: {juan.gamboa,eva.susana}@ufrpe.br
    
  

// Libraries
#include <string.h>
#include "TimerOne.h"
  
  const byte button = 2;  // Digital pin when is wired the button 
  const int led=13;
  const int gas_S1=A0;
  const int gas_S2=A1;
  const int gas_S3=A2;
  const int gas_S4=A3;
  const int gas_S5=A4;
  const int gas_S6=A5;
  const int air_pump=12;
  const int valve1=9;
  const int valve2=10;
  const int valve3=11;
  
  String data_received="";  
  char var[8];

  float time_conf=0;
  float sensor1;
  float sensor2;
  float sensor3;
  float sensor4;
  float sensor5;
  float sensor6;
  
  int state=0;
  int meter=0;
  int time_state1=10;
  int time_state2=20;
  int time_state3=10;
  
  bool button_status = false;  
  bool timeout=false;
  bool flag=false;
    
  void configuration(void); 
  bool send_data(float number);
  void to_receive(void);
  void tCallback (void) { timeout=true;}
  void push_button(void) {      
      button_status=true;
      delay(100);
      if (flag==false) {
        flag=true;
        state=1;
        meter=0;
      }
      }

  void setup() 
  {
    Serial.begin(38400);  //Open serial port communication 
    attachInterrupt(digitalPinToInterrupt(button),push_button,FALLING);
    Timer1.initialize(333333);
    Timer1.attachInterrupt(tCallback);
    pinMode(led, OUTPUT);
    pinMode(air_pump, OUTPUT);
    pinMode(valve1, OUTPUT);
    pinMode(valve2, OUTPUT);
    pinMode(valve3, OUTPUT);
     
  }


  void loop()
  {
          if (timeout)
          {
              meter++;
              if (state==2) 
              { timeout=false;
                read_sensor();
              }
                           
              timeout=false;
          }

          if (flag==true && state!=0 && meter==0)
          {
                configuration();
                delay(1000);         
          }

          if (state!=0 && meter!=0)
          {
            switch (state)
              {
                //gas concentration
                case 1: 
                if ((meter/3)>=time_state1)
                { state=2;
                  meter=0;
                }
                break;
                case 2:  
                if ((meter/3)>=time_state2) {
                  state=3;
                  meter=0;
                }
                break;
                case 3:  
                if ((meter/3)>=time_state3) {
                  state=4;
                  flag=false;
                  meter=0;
                }
                break;
                
              }            
          }
                 
          
  }		


void read_sensor(void)
{
    sensor1=analogRead(gas_S1)*5.0/1024.0;
    String fild="s1";
    send_data(sensor1,fild);
    delay(40);
    sensor2=analogRead(gas_S2)*5.0/1024.0;
    fild="s2";
    send_data(sensor2,fild);
    delay(40);
    sensor3=analogRead(gas_S3)*5.0/1024.0;
    fild="s3";
    send_data(sensor3,fild);
    delay(40);
    sensor4=analogRead(gas_S4)*5.0/1024.0;
    fild="s4";
    send_data(sensor4,fild);
    delay(40);
    sensor5=analogRead(gas_S5)*5.0/1024.0;
    fild="s5";
    send_data(sensor5,fild);
    delay(40);
    sensor6=analogRead(gas_S6)*5.0/1024.0;
    fild="s6";
    send_data(sensor6,fild);
}

void configuration(void)
{
            switch (state)
              {
                //gas concentration
                case 1: 
                       Serial.println("Gas concentration");
                       digitalWrite(air_pump,LOW);
                       digitalWrite(valve1,LOW);
                       digitalWrite(valve2,LOW);
                       digitalWrite(valve3,HIGH);
                       break;
                //measurement
                case 2:
                       Serial.println("Measurement");
                       digitalWrite(valve3,LOW); 
                       digitalWrite(air_pump,HIGH);
                       digitalWrite(valve1,HIGH);
                       digitalWrite(valve2,HIGH);
                       break;
                //purge        
                case 3:
                       Serial.println("Purge");
                       digitalWrite(air_pump,HIGH);
                       digitalWrite(valve1,HIGH);
                       digitalWrite(valve2,HIGH);
                       digitalWrite(valve3,HIGH); 
                       break;
                case 4:
                       Serial.println("Measurement finished");
                       digitalWrite(air_pump,LOW);
                       digitalWrite(valve1,LOW);
                       digitalWrite(valve2,LOW);
                       digitalWrite(valve3,LOW); 
                       flag=false;
                       state=0;
                       break;
              }
 
}

bool send_data(float number, String fild)
{
      dtostrf(number,2,2, var);
      Serial.flush();
      char cadena[4];
      fild.toCharArray(cadena,4);
      Serial.write(cadena);           
      Serial.write('\n');
      delay(1);
      Serial.flush();
      Serial.write(var);                    
      Serial.write('\n');
      delay(5);
      Serial.flush();
      digitalWrite(led,HIGH);
      return true;
}

void to_receive(void)
{
  Serial.flush();
    delay(5);
  if (Serial.read()=="conf")
  {
    data_received="";
    data_received=Serial.read();
    char cadena[4];
    data_received.toCharArray(cadena,4);
    time_conf = strtod(cadena,NULL);
  }
}