#include <usiTwiSlave.h>
#include <TinyWireS.h>

#define output (PB3)
#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;
}