Arduino Mega to 2x UNO over Serial - serialization

Question

Hi This is my first time posting, so bear with me.
My problem is with the serial communication between the Arduino Mega and 2x Arduino UNO's.
My setup comprises of a Mega as my master device and 1x UNO + Adafruit sound shield & 1x UNO + Adafruit Motor Shield. I have them via serial port i.e Serial1 RxTx on the mega to Serial TxRx on the UNO and same again for Serial2 for the other UNO, (I have x2 UNO's as both sheilds take up the whole PWM pin of the UNO)
Serial.begin(9600); //<--mega//
Serial1.begin(9600); //<--mega//
Serial2.begin(9600); //<--mega//
Serial.begin(9600); //<--UNO Sound//
Serial.begin(9600); //<--UNO motor//
Mega code:
Serial.println("Entering While loop1"); // Debug //
while(CommFlag1 == 0){
while (Serial2.available()){
SerialReceive2 = Serial2.read();
RxContent2.concat(SerialReceive2); //Store Content of Serial Data into Global Variable//
delay(10);
}
Serial.print("Sound MCU: "); // Debug //
Serial.println(RxContent2); // Debug //
delay(100); // Debug //
if (RxContent2 == "Alive$$$") {
Serial2.println("CommEst");
Serial.println("Alive Response Recieved Sound MCU"); // Debug //
RxContent2 = "";
CommFlag1 = 1;
}
}
Serial.println("Entering While loop2"); // Debug //
while(CommFlag2 == 0){
while (Serial1.available()){
SerialReceive1 = Serial1.read(); //Store Content of Serial Data into Global Variable//
RxContent1.concat(SerialReceive1);
delay(10);
}
Serial.print("Motor MCU: "); // Debug //
Serial.println(RxContent1); // Debug //
delay(100); // Debug //
if (RxContent1 == "Alive"){
Serial1.println("CommEst");
Serial.println("Alive Response Recieved Motor MCU");
RxContent1 = "";
CommFlag2 = 1;
}
}
UNO Code(Both are the same except the Serial.print statement which is Alive for the motor):
Serial.println("Alive$$$");
while(CommFlag == 0){
delay(250);
while (Serial.available()){
SerialReceive = Serial.read();
RxContent.concat(SerialReceive);
delay(50);
if (RxContent == "CommEst"){
CommFlag = 1;
RxContent = "";
}
}
}
In the serial window I can see the UNO's "alive$$$" response when PC is connected to the USB (Serial) on the mega, but the mega doesn't seem to accept the response value and doesn't execute the if statement?
Am I doing something wrong? Any help would be greatly appreciated!
Rich

Answer 1

In UNO code you send string by using Serial.println(), That means the string is prefix by \r\n character. But when you compare is not ending with \r\n. Please change if statement by add \r\n at the end of compare string.
if (RxContent2 == "Alive$$$\r\n")
and
if (RxContent1 == "Alive\r\n")
Or change code in UNO to print not println
Serial.print("Alive$$$");
and
Serial.print("Alive");