BUCK_FEEDBACK

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



int feedback = 3; //4
int PWM = 1;      //0

int pwm = 0;
float voltage = 0;
int voltage2 = 0;

void setup() {
  TinyWireS.begin(0x07);
  pinMode(feedback, INPUT);
  pinMode(PWM, OUTPUT);
  TCCR0B = TCCR0B & 0b11111000 | 0b001;
}

void loop() {
  if (TinyWireS.available()) {
    voltage2 = TinyWireS.receive();
    voltage = map(voltage2, 0, 255,0, 1024);
  }

  float output  = analogRead(feedback);

  if (voltage < output)
   {
    pwm = pwm-1;
    pwm = constrain(pwm, 0, 254);
   }

  if (voltage > output)
   {
    pwm = pwm+1;
    pwm = constrain(pwm, 0, 254);
   }
   analogWrite(PWM,pwm);
}