simple communication between AtTiny85 and Arduino (I2C)

Question

Hi I want to connect the arduino pro mini to my AtTiny85 over I2C.

The arduino should tell the attiny to switch a LED on or off. The arduino manages to switch the led on my attiny on but it never goes off.

I don't have any clue why?

Here is my Code for master and slave:

MASTER:

#include <Wire.h>
#define device (1)

void setup() {
  // put your setup code here, to run once:
  Wire.begin();
}

void loop() {
  // put your main code here, to run repeatedly:
  Wire.beginTransmission(device);
  Wire.write(1);
  Wire.endTransmission();
  delay(2000);
  Wire.write(0);
  Wire.endTransmission();
  delay(2000);
}

SLAVE:

#include <TinyWireS.h>
#include <usiTwiSlave.h>
#define output (4)
#define I2C_SLAVE_ADDR (1)


void setup() {
  // put your setup code here, to run once:
  TinyWireS.begin(I2C_SLAVE_ADDR);
  pinMode(output, OUTPUT);
}

volatile byte msg = 0;

void loop() {
  if(TinyWireS.available())
    msg = TinyWireS.receive();

  if(msg == 1)
    digitalWrite(output, HIGH);
  else if(msg == 0)
    digitalWrite(output, LOW);
  else
    msg = 0;
}

Answer 1

I finally found my mistake: when I do: Wire.write(0); I forgot to start the transmission with: Wire.beginTransmission(device);