Slave

#define I2C_SLAVE_ADDRESS 0x5 // Address of the slave

#include <TinyWireS.h>

int i=0;

void setup()
{
    TinyWireS.begin(I2C_SLAVE_ADDRESS); // join i2c network
    TinyWireS.onRequest(requestEvent);

}

void loop()
{
    // This needs to be here
    TinyWireS_stop_check();
}

// Gets called when the ATtiny receives an i2c request
void requestEvent()
{
    i = analogRead(A3);
    TinyWireS.send(i);
    //i++;
}