I have two Arduino boards and want to make them communicate with each other over serial. The code I have used for the two boards is almost identical.

• Every one second the "A" board sends a "ping" message over serial.
• The "B" board receives the "ping" message and responds with a "pong" one.
• The "A" board receives the "pong" message and prints it on screen.

Board A - ping code

String inputString = ""; 
boolean stringComplete = false; 
void setup() {
 Serial.begin(9600);
 inputString.reserve(200);
}
void loop() {
 Serial.print("ping");
 if (stringComplete) {
 Serial.println(inputString);
 inputString = "";
 stringComplete = false;
 }
 delay(1000);
}
void serialEvent() {
 while (Serial.available()) {
 char inChar = (char)Serial.read();
 inputString += inChar;
 if (inChar == 'g') {
 stringComplete = true;
 }
 }
}

Board B - pong code

String inputString = ""; 
boolean stringComplete = false; 
void setup() {
 Serial.begin(9600);
 inputString.reserve(200);
}
void loop() {
 if (stringComplete) {
 Serial.println("pong");
 inputString = "";
 stringComplete = false;
 }
}
void serialEvent() {
 while (Serial.available()) {
 char inChar = (char)Serial.read();
 inputString += inChar;
 if (inChar == 'g') {
 stringComplete = true;
 }
 }
} 

The code seems to work, but not exactly as expected. I initiate the serial monitor of the board "A" and expect to see every one second:

pingpong

Instead I see this:

pingpong

pong

pong

....

which means that the pong message is repeated more than one time per second. But I want the "B" board to transmit the "pong" message only when it receives the "ping" one.

Why is this happening? Is there an error in the code? Is there a detail about the serial protocol which escapes me?

Any thoughts would be appreciated.

I have two Arduino boards and want to make them communicate with each other over serial. The code I have used for the two boards is almost identical.

• Every one second the "A" board sends a "ping" message over serial.
• The "B" board receives the "ping" message and responds with a "pong" one.
• The "A" board receives the "pong" message and prints it on screen.

Board A - ping code

String inputString = ""; 
boolean stringComplete = false; 
void setup() {
 Serial.begin(9600);
 inputString.reserve(200);
}
void loop() {
 Serial.print("ping");
 if (stringComplete) {
 Serial.println(inputString);
 inputString = "";
 stringComplete = false;
 }
 delay(1000);
}
void serialEvent() {
 while (Serial.available()) {
 char inChar = (char)Serial.read();
 inputString += inChar;
 if (inChar == 'g') {
 stringComplete = true;
 }
 }
}

Board B - pong code

String inputString = ""; 
boolean stringComplete = false; 
void setup() {
 Serial.begin(9600);
 inputString.reserve(200);
}
void loop() {
 if (stringComplete) {
 Serial.println("pong");
 inputString = "";
 stringComplete = false;
 }
}
void serialEvent() {
 while (Serial.available()) {
 char inChar = (char)Serial.read();
 inputString += inChar;
 if (inChar == 'g') {
 stringComplete = true;
 }
 }
} 

The code seems to work, but not exactly as expected. I initiate the serial monitor of the board "A" and expect to see every one second:

pingpong

Instead I see this:

pingpong

pong

pong

....

which means that the pong message is repeated more than one time per second. But I want the "B" board to transmit the "pong" message only when it receives the "ping" one.

Why is this happening? Is there an error in the code? Is there a detail about the serial protocol which escapes me?

Any thoughts would be appreciated.

I have two Arduino boards and want to make them communicate with each other over serial. The code i have used for the two boards is almost identical.

• Every one second the "A" board sends a "ping" message over serial.
• The "B" board receives the "ping" message and responds with a "pong" one.
• The "A" board receives the "pong" message and prints it on screen.

Board A - ping code

String inputString = ""; 
boolean stringComplete = false; 
void setup() {
 Serial.begin(9600);
 inputString.reserve(200);
}
void loop() {
 Serial.print("ping");
 if (stringComplete) {
 Serial.println(inputString);
 inputString = "";
 stringComplete = false;
 }
 delay(1000);
}
void serialEvent() {
 while (Serial.available()) {
 char inChar = (char)Serial.read();
 inputString += inChar;
 if (inChar == 'g') {
 stringComplete = true;
 }
 }
}

Board B - pong code

String inputString = ""; 
boolean stringComplete = false; 
void setup() {
 Serial.begin(9600);
 inputString.reserve(200);
}
void loop() {
 if (stringComplete) {
 Serial.println("pong");
 inputString = "";
 stringComplete = false;
 }
}
void serialEvent() {
 while (Serial.available()) {
 char inChar = (char)Serial.read();
 inputString += inChar;
 if (inChar == 'g') {
 stringComplete = true;
 }
 }
} 

The code seems to work, but not exactly as expected. I initiate the serial monitor of the board "A" and expect to see every one second:

pingpong

Instead I see this:

pingpong

pong

pong

....

which means that the pong message is repeated more than one time per second. But I want the "B" board to transmit the "pong" message only when it receives the "ping" one.

Why is this happening? Is there an error in the code? Is there a detail about the serial protocol which escapes me?

Any thoughts would be appreciated.

I have two Arduino boards and want to make them communicate with each other over serial. The code I have used for the two boards is almost identical.

• Every one second the "A" board sends a "ping" message over serial.
• The "B" board receives the "ping" message and responds with a "pong" one.
• The "A" board receives the "pong" message and prints it on screen.

Board A - ping code

String inputString = ""; 
boolean stringComplete = false; 
void setup() {
 Serial.begin(9600);
 inputString.reserve(200);
}
void loop() {
 Serial.print("ping");
 if (stringComplete) {
 Serial.println(inputString);
 inputString = "";
 stringComplete = false;
 }
 delay(1000);
}
void serialEvent() {
 while (Serial.available()) {
 char inChar = (char)Serial.read();
 inputString += inChar;
 if (inChar == 'g') {
 stringComplete = true;
 }
 }
}

Board B - pong code

String inputString = ""; 
boolean stringComplete = false; 
void setup() {
 Serial.begin(9600);
 inputString.reserve(200);
}
void loop() {
 if (stringComplete) {
 Serial.println("pong");
 inputString = "";
 stringComplete = false;
 }
}
void serialEvent() {
 while (Serial.available()) {
 char inChar = (char)Serial.read();
 inputString += inChar;
 if (inChar == 'g') {
 stringComplete = true;
 }
 }
} 

The code seems to work, but not exactly as expected. I initiate the serial monitor of the board "A" and expect to see every one second:

pingpong

Instead I see this:

pingpong

pong

pong

....

which means that the pong message is repeated more than one time per second. But I want the "B" board to transmit the "pong" message only when it receives the "ping" one.

Why is this happening? Is there an error in the code? Is there a detail about the serial protocol which escapes me?

Any thoughts would be appreciated.