#include <SoftwareSerial.h>

//TX , PA0 , could be A0, 0 , 10
//RX , PA1 , could be A1 , 1 , 9


const int mosfet = 7; // connected to PA7 or 7 in arduino
const int phototransistor = 8; // connected to PB2 or 8 in arduino

int value = 0;
int timing = 50;

SoftwareSerial mySerial(0, A1); // RX, TX

void setup() {

  pinMode(mosfet, OUTPUT);

}

void loop() { 

  for (value = 0; value <= 255; value += 1) { 

    analogWrite(mosfet, value);             
    delay(timing);                     
  }
  for (value = 180; value >= 0; value -= 1) { 
    analogWrite(mosfet, value);
    delay(timing);
  }

}