How do I send a string to master using i2c

Question

I want to write an Arduino program that simply recieves a string (via the I2C wire library) from a master Arduino, then waits for a request, and sends that string back.

Here is my code:

#include <Wire.h>
void setup()
{
 Wire.begin(4); 
 Wire.onReceive(receiveEvent); 
 Wire.onRequest(requestEvent);
}
String data = "";
void loop()
{
}
void receiveEvent(int howMany)
{
 data = "";
 while( Wire.available()){
 data += (char)Wire.read();
 }
}
void requestEvent()
{
 Wire.write(data);
}

I read in the API that the write() function accepts a string, but I keep getting a "No matching function for call" error. I tried to simply replace

Wire.write(data);

with

Wire.write("test");

and that worked without error. Why is this the case?

• newy8: Try this instead of wire.write(data); wire.print(data)

Answer 1

data is a String. "test" is a char*. Wire.write() has no prototype that takes a String.

Wire.write(data.c_str());

• opu 웃: working perfectly :)