int i;          // counter variable 
int j;          // pgm outputs codes 00000 to 00111 in portd 2-4 bits
int count=7;
int SW1=8;      //Set SW1 to Pin 8
int SW2=9;      //Set SW2 to Pin 9

void setup(){
 DDRD = DDRD | B00011100;    // set direction bits for pins 2 to 4, leave 0 and 1 untouched
 //(xx | 00 = xx)  same as pinMode(pin, OUTPUT) for pins 2 to 4
 Serial.begin(9600); 
 Serial.println ("Question 7");
 Serial.println ("Current Limiting Resistor = 5-3/0.04=75, 5-3/0.01=200");
 Serial.println("Therefore, using a 220 ohm resistor so bright enough to use and don't exceed 200mA maximum");
 Serial.println ("Yellow switch = Up Counter,  Green Switch = Down Counter");
 pinMode(SW1,INPUT);
 pinMode(SW2,INPUT);
 digitalWrite(SW1, HIGH);                       //enable pullup. Switch connected to ground
 digitalWrite(SW2, HIGH);                       //enable pullup. Switch connected to ground
} 

void loop(){  
  while (digitalRead(SW1)==LOW)                 // check if COUNT_UP switch is released
  {
    count++;
    if (count>7)
    {
      count=0;
    }
    
    // 3 bits manipulated 0 to 7
    PORTD = PORTD & B11100011;                  // clear out bits 2 -4, leave pins 0 and 1 untouched (xx & 11 = xx)
    j = (count << 2);                           // shift variable up to pins 2 - 7 - to avoid pins 0 and 1
    PORTD = PORTD | j;                         // combine the port information with the new information for LED pins 
    Serial.print("PORTD in Binary=");
    Serial.print(PORTD, BIN);                // debug to show masking 
    Serial.print(",  Count=");
    Serial.println(count);
  
    delay(200); 
    
  }
  while (digitalRead(SW2)==LOW)            // check if COUNT_DOWN switch is released
  {
    count--;
    if (count<0)  // Restart after 7
    { 
     count=7;
    }
    // 3 bits manipulated 0 to 7
    PORTD = PORTD & B11100011;          // clear out bits 2 -4, leave pins 0 and 1 untouched (xx & 11 = xx)
    j = (count << 2);                   // shift variable up to pins 2 - 7 - to avoid pins 0 and 1
    PORTD = PORTD | j;                 // combine the port information with the new information for LED pins 
    Serial.print("PORTD in Binary=");
    Serial.print(PORTD, BIN);           // debug to show masking 
    Serial.print(",  Count=");
    Serial.println(count);
    delay(200); 

  }
  delay(200);
}