Always 255-response in I2C between ATTiny85 (8MHz) and Arduino Uno I tried to set up an I2C conversation between ab ATTiny85 (8MHz) and an Arduino Uno. However I always get a 255 response from my I2C slave. I am using Arduino 1.8.5.

What am I doing wrong?

ATTiny85-Slave Code:

#include "TinyWireS.h"  // wrapper class for I2C slave 
routines
#define I2C_SLAVE_ADDR  0x26 // i2c slave address (38)

byte t=10;

void setup() {
  TinyWireS.begin(I2C_SLAVE_ADDR);  // init I2C Slave mode
  TinyWireS.onRequest(requestEvent);
}

void loop() {
}

void requestEvent() {
  TinyWireS.send(t);
}


Arduino Uno-Master Code:

 #include &lt;Wire.h&gt;
 #define I2C_SLAVE_ADDR  0x26 // i2c slave address (38)

void setup() {
  Wire.begin();
  Serial.begin(9600);
}

void loop() {
  byte num;
  // read 1 byte, from address 0x26
  Wire.requestFrom(I2C_SLAVE_ADDR, 1);
  while(Wire.available()) {
    num = Wire.read();
  }
  Serial.print("num = ");
  Serial.println(num,DEC);
}
It may seem that the current commit of January 2018 from the TinyWire library is corrupt. Try using an older version from 2017, for example this one: https://github.com/rambo/TinyWire/tr...72a13504bbfc4e

This solves the problem for me as well.

Source: Teensy 3.5 - I2C - ATTiny85-20PU (TinyWireS.OnRequest not triggering!) - Post #11