Wire.write head scratcher

Using Arduino Programming Questions
1

I've been using Structs to send data between two UNOs successfully for a while now. Recently I tried to switch from a MasterSender/SlaveReader configuration to a MasterReader/SlaveSender configuration.

In doing so, my true and tested method of sending a Struct byte-wise through the wire started giving weird results. In debugging my original code and trying to reduce it to the simplest form that would give me the error I arrived at the attached code.

If you look in the void requestEvent() function you will see that I commented out a Wire.write("12"); command, and substitute it by two byte-wise commands, sending '1' and '2' separately. When I execute the code with the Wire.write("12"); the results on the other end are as expected (i.e., the Master Reader obtains "12"). However, if i try to send each digit individually, then I get the same garbage every time (I get the digit "2" followed by the character "ÿ" regardless of what bytes I send). I should note that I also tried sending ("1") instead of ('1') but the results were the same.

Help please!!!

#include <Wire.h>


void setup()
{
  Wire.begin(8);                // join i2c bus with address #8
  Wire.onRequest(requestEvent); // register event
}

void loop()
{
  delay(100);
}

// function that executes whenever data is requested by master
// this function is registered as an event, see setup()
void requestEvent()
{

Wire.write('1');
Wire.write('2');
//Wire.write("12");

}
2

BTW, for reference, here's the master reader side code:

#include <Wire.h>

void setup()
{
  Wire.begin();        // join i2c bus (address optional for master)
  Serial.begin(9600);  // start serial for output
}

void loop()
{
  Wire.requestFrom(8, 2);    // request 2 bytes from slave device #8

  while (Wire.available())   // slave may send less than requested
  {
    char c = Wire.read(); // receive a byte as character

    delay(100);
    Serial.print(c);         // print the character
    delay(100);
  }

  delay(500);
}
3

Never mind... problem solved. Forgot to include length of data on the Wire.write command...

4

Can you post the working code for future reference?

Thanks