Serial communication between 2 arduino's doesn't works when Sending string in a program with a lot of functions

Question

Note :

This question is completely different from the questions that I have asked before although the code snippets might be the same, So please do not waive it as a duplicate right when you see it.

In my setup I have connected two arduino's Serially. An Arduino Mega is the one that is sending the string and a Arduino Uno is the one that's receiving it.

• Arduino Mega : TX1(19),RX1(18) - Serial1
• Arduino Uno : RX(10),TX(11) - using SoftwareSerial
• Gnd is connecetd on both boards

Arduino UNO - code is same for both cases

#include <SoftwareSerial.h>
SoftwareSerial s(10, 11);
void setup() 
{
 delay(200);
 Serial.begin(9600);
 Serial1.begin(9600); 
 s.begin(9600);
 while (!Serial) ; // wait for Arduino Serial Monitor 
}
void loop() 
{ 
 if(s.available()>0)
 {
 Serial.print("\nrec\n");
 delay(100);
 String b = s.readStringUntil('\n');
 delay(100);
 Serial.print(b);
 delay(40);
 }

}

When the code in my arduino mega has only a print statement to send a string an infinite no. of times to the Uno, The Uno is receiving the string properly.

Arduino Mega

void setup()
{
 Serial1.begin(9600);
}
void loop() 
{
 Serial1.println("e2e4"); 
 delay(100);
}

Now when I send the string an infinite no. of times from the Arduino mega but this time the mega has a lot more functions included in the program as well. In this case the Uno does not receive the string sent.

Arduino Mega - code containing a lot of functions and sedning a string to Uno

int SensorValStore_Prev[8][8] = { {0,0,0,0,0,0,0,0}, \
 {0,0,0,0,0,0,0,0}, \
 {1,1,1,1,1,1,1,1}, \
 {1,1,1,1,1,1,1,1}, \
 {1,1,1,1,1,1,1,1}, \
 {1,1,1,1,1,1,1,1}, \
 {0,0,0,0,0,0,0,0}, \
 {0,0,0,0,0,0,0,0} };
int SensorValStore_Curr[8][8]={ {0,0,0,0,0,0,0,0}, \
 {0,0,0,0,0,0,0,0}, \
 {1,1,1,1,1,1,1,1}, \
 {1,1,1,1,1,1,1,1}, \
 {1,1,1,1,1,1,1,1}, \
 {1,1,0,1,1,1,1,1}, \
 {0,0,0,0,0,0,0,0}, \
 {0,1,0,0,0,0,0,0} };
//int SensorValStore_Curr[8][8];
int sum1[8],sum2[8],temp[8][8],k,l,i,j,rank,nextRow;
String file,moveSan,Temp,bestMove;
char Buffer[20];
void doAction();
void ReadSensor();
void Difference();
void binToIntCalc();
void check();
void getMovePlayed();
void SendMove();
void getMove();
void setup()
{
 Serial.begin(9600);
 lcd.begin(16,2);
 pinMode(22,INPUT_PULLUP); // Reed switch - Row1
 pinMode(24,INPUT_PULLUP); // Reed switch - Row2
 pinMode(26,INPUT_PULLUP); // Reed switch - Row3
 pinMode(28,INPUT_PULLUP); // Reed switch - Row4
 pinMode(30,INPUT_PULLUP); // Reed switch - Row5 
 pinMode(32,INPUT_PULLUP); // Reed switch - Row6 
 pinMode(34,INPUT_PULLUP); // Reed switch - Row7 
 pinMode(36,INPUT_PULLUP); // Reed switch - Row8 
 pinMode(2,INPUT_PULLUP);// Push Button
 pinMode(38,OUTPUT);
 pinMode(40,OUTPUT);
 pinMode(42,OUTPUT);
 pinMode(44,OUTPUT);
 pinMode(46,OUTPUT);
 pinMode(48,OUTPUT);
 pinMode(50,OUTPUT);
 pinMode(52,OUTPUT);
 pinMode(3,OUTPUT);
 digitalWrite(38,HIGH);
 digitalWrite(40,HIGH);
 digitalWrite(42,HIGH);
 digitalWrite(44,HIGH);
 digitalWrite(46,HIGH);
 digitalWrite(48,HIGH);
 digitalWrite(50,HIGH);
 digitalWrite(52,HIGH);
 digitalWrite(3,LOW);
}
void loop()
{
 // doAction();
 delay(40);
 Difference();
 delay(40);
 binToIntCalc();
 delay(40);
 check();
 delay(40);
 getMovePlayed();
 delay(40);
 getMove();
 delay(40);
 //}
}
void Print(int matrix[8][8])
{
 for(i=0;i<8;i++)
 {
 for(j=0;j<8;j++)
 {
 Serial.print(matrix[i][j]);
 Serial.print(" ");
 }
 Serial.println();
 }
}
void doAction()
{
 nextRow = 0;
 for(i=0;i<8;i++)
 {
 digitalWrite(38 + nextRow,LOW);
 delay(40);
 ReadSensor(i);
 digitalWrite(38 + nextRow,HIGH);
 delay(40);
 nextRow +=2;
 }
}
void ReadSensor(int iter) 
{
 delay(10);
 for(j=0;j<8;j++)
 SensorValStore_Curr[iter][j] = digitalRead(j+2);
}
void Difference()
{
 for(i=0;i<8;i++)
 for(j=0;j<8;j++)
 temp[i][j] = abs(SensorValStore_Curr[i][j] - SensorValStore_Prev[i[j]);
}
void binToIntCalc()
{
 for(i=0;i<8;i++)
 for(j=0;j<8;j++)
 {
 sum1[i] += pow(2,j)*SensorValStore_Prev[i][j];
 sum2[i] += pow(2,j)*SensorValStore_Curr[i][j];
 }
 }
void check()
{
 k=0;
 l=0;
 for(i=0;i<8;i++)
 { 
 if(sum2[i]>sum1[i])
 k = i;
 if(sum2[i]<sum1[i])
 l = i;
 delay(40);
 }
}
void getMovePlayed()
{
 for(j=0;j<8;j++)
 {
 if(temp[k][j] == 1)
 {
 rank =k+1;
 file = String(char(97+j));
 delay(40);
 moveSan = file + rank;
 Temp = moveSan;
 }
 }
 for(j=0;j<8;j++)
 { 
 if( temp[l][j] == 1)
 {
 rank =l+1;
 file = String(char(97+j));
 delay(40);
 moveSan = file + rank;
 Temp.concat(moveSan);
 }
 }
}
void SendMove(String movePlayed)
{
 Serial.println("start");
 Serial.print(movePlayed);
 Serial.println();
}
void getMove() // SENDING STRING TO THE ARDUINO UNO
{
 while(1){
 Serial1.println("e2e4"); 
 delay(100);
 }
}

Note: getMove() is the function that sends the string to the arduino through Serial1

• chrisl: I don't see a Serial1.begin()
• roaibrain: damn....I can't believe that I made such a ridiculous error. @chrisl should I just delete this question . Since it will have absolutely no use to this site.

Answer 1

My answer might not be what you'd expect but I'll try anyway.

Did you troobleshoot your serial communications ? Try doing a simple programm for both cards and try sending data from one to another.

Uno code

#include <SoftwareSerial.h>
#define rxPin 10
#define txPin 11
SoftwareSerial s(rxPin, txPin);
String buff = "";
void setup()
{
 s.begin(9600);
 Serial.begin(9600);
}
void loop()
{
 if(Serial.available)
 {
 while(Serial.available())
 {
 buff += char(Serial.read());
 }
 s.print(buff);
 buff="";
 }
 if(s.available)
 {
 while(s.available())
 {
 buff += char(s.read());
 }
 Serial.print(buff);
 buff = "";
 }
}

Mega code

String buff = "";
void setup()
{
 Serial1.begin(9600);
 Serial.begin(9600);
}
void loop()
{
 if(Serial.available)
 {
 while(Serial.available())
 {
 buff += char(Serial.read());
 }
 Serial1.print(buff);
 buff="";
 }
 if(Serial1.available)
 {
 while(Serial1.available())
 {
 buff += char(Serial1.read());
 }
 Serial.print(buff);
 buff = "";
 }
}

Did you double check your connections ? Tx (mega) to rx (uno) and rx (mega) to tx(uno)

In your setup() on your arduino mega

void setup()
{
 Serial.begin(9600);
 lcd.begin(16,2);
 pinMode(22,INPUT_PULLUP); // Reed switch - Row1
 pinMode(24,INPUT_PULLUP); // Reed switch - Row2
 pinMode(26,INPUT_PULLUP); // Reed switch - Row3
 pinMode(28,INPUT_PULLUP); // Reed switch - Row4
 pinMode(30,INPUT_PULLUP); // Reed switch - Row5 
 pinMode(32,INPUT_PULLUP); // Reed switch - Row6 
 pinMode(34,INPUT_PULLUP); // Reed switch - Row7 
 pinMode(36,INPUT_PULLUP); // Reed switch - Row8 
 pinMode(2,INPUT_PULLUP);// Push Button
 pinMode(38,OUTPUT);
 pinMode(40,OUTPUT);
 pinMode(42,OUTPUT);
 pinMode(44,OUTPUT);
 pinMode(46,OUTPUT);
 pinMode(48,OUTPUT);
 pinMode(50,OUTPUT);
 pinMode(52,OUTPUT);
 pinMode(3,OUTPUT);
 digitalWrite(38,HIGH);
 digitalWrite(40,HIGH);
 digitalWrite(42,HIGH);
 digitalWrite(44,HIGH);
 digitalWrite(46,HIGH);
 digitalWrite(48,HIGH);
 digitalWrite(50,HIGH);
 digitalWrite(52,HIGH);
 digitalWrite(3,LOW);
}

I don't see the Serial1.begin(9600) as said by @chrisl but you mentionned it above.

I hope this helps, sorry if I've not solved your problem.

• roaibrain: you are correct, I missed it out in my code.