what is Serial.read() returning?

Forum 2005-2010 (read only) Hardware Troubleshooting
1

I've written a small routine that should wait for a signal over serial before the program begins. It goes like:

boolean connectionEstablished = false;
byte connectByte=0;
void establishContact() {
while (!connectionEstablished){
if (Serial.available()>0){
connectByte = Serial.read();
if (connectByte=='X'){
Serial.println("Connection accepted");
connectionEstablished=true;
}else{
Serial.println("Invalid connection attempt:");
Serial.println(connectByte,DEC);
}
}else{
Serial.println("waiting for start signal");
}
delay(200);
}
}

Basically the program should wait for the character 'X' before leaving that while loop. This is a simple extension of the SerialCallResponse example.

The problem is that both this and that example exit the while loop if nothing is connected. I am using the bluetooth arduino. If I initiate a connection to the modem over bluetooth before the program starts then it waits in the loop as expected. If I don't have something connected then somehow the loop terminates. It is mind boggling!

If anyone has any ideas of what is happening here I'd love to hear them!

Regards,
Kallin Nagelberg.

2

If nothing is connected, how do you know the while loop is exited? :-?

3

I have an LED that is triggered after the loop is exited.'

I changed the loop to the following and it's functioning as expected. Still have no idea why the other way didn't work though,,

boolean connectionEstablished = false;
byte connectByte=0;
void establishContact() {
while (!connectionEstablished){
while (Serial.available() <= 0) {
Serial.print('A', BYTE); // send a capital A
delay(300);
}

connectByte = Serial.read();
if (connectByte=='X'){
Serial.println("Connection accepted");
connectionEstablished=true;
}else{
Serial.println("Invalid connection attempt:");
Serial.println(connectByte,DEC);
}

delay(200);
}
}

4

Huh. That's strange. Is it possible radio noise ended up as an 'X'? Does BlueTooth take care of reliably transmitting data?