Problem with XBee Series 2 communication between Mega and Uno

Projects Networking, Protocols, and Devices
1

I followed this tutorial: http://www.instructables.com/id/Arduino-Wireless-SD-Shield-Tutorial/?ALLSTEPS
but it is not working for me.

Setup
Transmitter:

  • Mega 2560
  • Arduino Wireless Protoshield SD
  • XBee 2mW Wire Antenna - Series 2 (ZigBee Mesh)

Code:

void setup() {
  // initialize serial communication:
  Serial.begin(9600); 
}

void loop(){

  delay(1000); 
  Serial.println('h');
  delay(1000);   
}

I have the switch on the shield on "USB" while uploading and can see "h"'s printed in the serial window after uploading. Switching to "Micro" after that.

Receiver:

  • Uno R3
  • Arduino Wireless Protoshield SD
  • XBee 2mW Wire Antenna - Series 2 (ZigBee Mesh)

Code:

int sentDat;

void setup() {
  Serial.begin(9600);   
  pinMode(2, OUTPUT); 
}

void loop() {
  if (Serial.available() > 0) {
	sentDat = Serial.read(); 

	if(sentDat == 'h'){
  	  digitalWrite(2, HIGH);
          delay(1000);
          digitalWrite(2, LOW);
	}
  }
}

Again, having the switch to USB when uploading and seeing the led blink when sending an "h" over serial. Then switching to "Micro".

And then: Nothing!

How can I troubleshoot this?

2

How can I troubleshoot this?

Skip the xbee for the time being and do testing between the two using wire between the tx/rx/gnd on the boards. Once that works, then add the xbees. Below is some simple arduino to arduino serial test code.

//zoomkat 3-5-12 simple delimited ',' string tx/rx 
//from serial port input (via serial monitor)
//and print result out serial port
//Connect the sending arduino rx pin to the receiving arduino rx pin. 
//Connect the arduino grounds together. 
//What is sent to the tx arduino is received on the rx arduino.
//Open serial monitor on both arduinos to test

String readString;

void setup() {
  Serial.begin(9600);
  Serial.println("serial delimit test 1.0"); // so I can keep track of what is loaded
}

void loop() {

  //expect a string like wer,qwe rty,123 456,hyre kjhg,
  //or like hello world,who are you?,bye!,

  if (Serial.available())  {
    char c = Serial.read();  //gets one byte from serial buffer
    if (c == ',') {
      if (readString.length() >1) {
        Serial.print(readString); //prints string to serial port out
        Serial.println(','); //prints delimiting ","
        //do stuff with the captured readString 
        readString=""; //clears variable for new input
      }
    }  
    else {     
      readString += c; //makes the string readString
    }
  }
}
3

@zoomkat thanks for your answer. it made me think...

I yanked the shield from the mega and crossed tx/rx from the Mega to the shield. I also connected the 6 isp connections plus 5v, 3.3v and GND from the mega to the shield.
I then connected mega's rx with uno's rx and tx with tx with wires and my blink sketch worked!
I had the switches on the shields both to USB (http://arduino.cc/en/Main/ArduinoWirelessShield)

but then, when I remove the rx/tx wires the communication is dead. I switched the shield to Micro mode and back to USB, i played around with switching rx / tx... but no luck.

not sure if I need to make more connections from the mega to the shield... unfortunately it's not on shieldlist.org.