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Instead of repeating several calls to digitalwrite you should consider changing the pins directly as described here.

This now depends on which port your LEDs are connected to. Assuming port D you would use DDRD to define the pins as output (usually in setup()) and PORTD to set their values (in loop), e.g.

DDRD = B11111110; // define pins 1..7 as outputs, pin 0 as input

and

PORTD = B11110000; // switch on first 4 LEDs

Now all you need to do is to write a function to map your number range to suitable bit strings.

The function could look like this:

int convert(int n) {                                                                     

  int res = 0;   // start with all pins off (zero)
  while (n > 0) {// repeat while n not (yet) zero
    res <<= 1;   // shift pattern 1 bit (i.e. pin) to the left
    res |= 1;    // "switch on" lowest pin 
    n -= 100;    // defines step size (1 LED for every  100)
  }
  return res;

}

It takes your value and returns an int that you can assign to the port. I.e. for 0 it returns 0, for 1..100 it returns 1, for 101..200 it returns 3 = B11, for 201..300 it returns 7 = B111 and so on. (Note that it does not do any sanity checks on the input / output but that's certainly easy for you to add if needed.)

Instead of repeating several calls to digitalwrite you should consider changing the pins directly as described here.

This now depends on which port your LEDs are connected to. Assuming port D you would use DDRD to define the pins as output (usually in setup()) and PORTD to set their values (in loop), e.g.

DDRD = B11111110; // define pins 1..7 as outputs, pin 0 as input

and

PORTD = B11110000; // switch on first 4 LEDs

Now all you need to do is to write a function to map your number range to suitable bit strings.

The function could look like this:

int convert(int n) {                                                                     

  int res = 0;   // start with all pins off (zero)
  while (n > 100) { 
    res <<= 1;   // shift pattern 1 bit (i.e. pin) to the left
    res |= 1;    // "switch on" lowest pin 
    n -= 100;    // defines step size (1 LED for every  100)
  }
  return res;

}

It takes your value and returns an int that you can assign to the port. I.e. for 0..100 it returns 0, for 101..200 it returns 1, for 201..300 it returns 3 = B11, for 301..400 it returns 7 = B111 and so on. (Note that it does not do any sanity checks on the input / output but that's certainly easy for you to add if needed.)

(In response to comment: Note that the bit pattern I use as example for DDRD above is an example: It sets bit / pin 0 as input. If you use convert you would, of course, set the lowest bit of DDRD to 1 to make it an output.)

Instead of repeating several calls to digitalwrite you should consider changing the pins directly as described here.

This now depends which port your LEDs are connected to. Assuming port D you would use DDRD to define the pins as output (usually in setup()) and PORTD to set their values (in loop), e.g.

DDRD = B11111110; // define pins 1..7 as outputs, pin 0 as input

and

PORTD = B11110000; // switch on first 4 LEDs

Now all you need to do is to write a function to map your number range to suitable bit strings.

The function could look like this:

int convert(int n) {                                                                     

  int res = 0;
  while (n > 0) {
    res <<= 1;   
    res |= 1;    
    n -= 100;    
  }
  return res;

}

It takes your value and returns an int that you can assign to the port. I.e. for 0 it returns 0, for 1..100 it returns 1, for 101..200 it returns 3 = B11, for 201..300 it returns 7 = B111 and so on. (Note that it does not do any sanity checks on the input / output but that's certainly easy for you to add if needed.)

Instead of repeating several calls to digitalwrite you should consider changing the pins directly as described here.

This now depends on which port your LEDs are connected to. Assuming port D you would use DDRD to define the pins as output (usually in setup()) and PORTD to set their values (in loop), e.g.

DDRD = B11111110; // define pins 1..7 as outputs, pin 0 as input

and

PORTD = B11110000; // switch on first 4 LEDs

Now all you need to do is to write a function to map your number range to suitable bit strings.

The function could look like this:

int convert(int n) {                                                                     

  int res = 0;   // start with all pins off (zero)
  while (n > 0) {// repeat while n not (yet) zero
    res <<= 1;   // shift pattern 1 bit (i.e. pin) to the left
    res |= 1;    // "switch on" lowest pin 
    n -= 100;    // defines step size (1 LED for every  100)
  }
  return res;

}

It takes your value and returns an int that you can assign to the port. I.e. for 0 it returns 0, for 1..100 it returns 1, for 101..200 it returns 3 = B11, for 201..300 it returns 7 = B111 and so on. (Note that it does not do any sanity checks on the input / output but that's certainly easy for you to add if needed.)

Instead of repeating several calls to digitalwrite you should consider changing the pins directly as described here.

This now depends which port your LEDs are connected to. Assuming port D you would use DDRD to define the pins as output (usually in setup()) and PORTD to set their values (in loop), e.g.

DDRD = B11111110; // define pins 1..7 as outputs, pin 0 as input

and

PORTD = B11110000; // switch on first 4 LEDs

Now all you need to do is to write a function to map your number range to suitable bit strings.

Instead of repeating several calls to digitalwrite you should consider changing the pins directly as described here.

This now depends which port your LEDs are connected to. Assuming port D you would use DDRD to define the pins as output (usually in setup()) and PORTD to set their values (in loop), e.g.

DDRD = B11111110; // define pins 1..7 as outputs, pin 0 as input

and

PORTD = B11110000; // switch on first 4 LEDs

Now all you need to do is to write a function to map your number range to suitable bit strings.

The function could look like this:

int convert(int n) {                                                                     

  int res = 0;
  while (n > 0) {
    res <<= 1;   
    res |= 1;    
    n -= 100;    
  }
  return res;

}

It takes your value and returns an int that you can assign to the port. I.e. for 0 it returns 0, for 1..100 it returns 1, for 101..200 it returns 3 = B11, for 201..300 it returns 7 = B111 and so on. (Note that it does not do any sanity checks on the input / output but that's certainly easy for you to add if needed.)