Simplify if then else statements for Neopixel/compass project

Question

I am working on a project where a rotary encoder is generating 0 - 359° output and I am feeding that to a 60 Neopixel ring but I need a way to simplify or come up with a better way of a bunch of if-then-else statements. Here is some sample code.

// NeoPixel Display   
  if ((counter >=3) && (counter <=9))
(
  strip.setPixelColor(0, 255, 0, 0); //set pixel number 1 and set color to red
  strip.show(); //send color to pixel 1 on NeoPixel Ring  
)
else if strip.setPixelColor(0, 0, 0, 0);
        strip.show();

  if ((counter >=10) && (counter <=15))
(
  strip.setPixelColor(1, 255, 0, 0); //set pixel number 2 and set color to red
  strip.show(); //send color to pixel 2 on NeoPixel Ring  
)
else if strip.setPixelColor(1, 0, 0, 0);
        strip.show();

  if ((counter >=16) && (counter <=21))
(
  strip.setPixelColor(2, 255, 0, 0); //set pixel number 3 and set color to red
  strip.show(); //send color to pixel 3 on NeoPixel Ring  
)
else if strip.setPixelColor(2, 0, 0, 0);
        strip.show();

score 3 · Answer 1 · edited Sep 22 '18 at 17:33

You don't use the correct syntax. I assume you mean:

// NeoPixel Display   
if ((counter >=3) && (counter <=9))
{
  strip.setPixelColor(0, 255, 0, 0); //set pixel number 1 and set color to red
  strip.show(); //send color to pixel 1 on NeoPixel Ring  
}
else 
{
  strip.setPixelColor(0, 0, 0, 0)
  strip.show();
}

And similar for the other colors.

First you see there are a lot of occurences of calls to setPixelColor and show. We make a function of this, where the color and the red value is parameterized:

void setPixel(int pixelNumber, int red)
{
  strip.setPixelColor(pixelNumber, red, 0, 0);
}

Now we can write your code as

// NeoPixel Display   
if ((counter >=3) && (counter <=9))
{
  setPixel(0, 255);
}
else
{
  setPixel(0, 0);
}

void setPixel(int pixelNumber, int red)
{
  strip.setPixelColor(pixelNumber, red, 0, 0);
  strip.show();
}

And similar for the other colors.

Now we get rid of the if statements. For the first color this will become:

// NeoPixel Display   
setPixel(0, ((counter >= 3) && (counter <= 9)) ? 255 : 0);

Combined with the other colors we get

// NeoPixel Display   
setPixel(0, ((counter >=  3) && (counter <=  9)) ? 255 : 0);
setPixel(1, ((counter >= 10) && (counter <= 15)) ? 255 : 0);
setPixel(2, ((counter >= 16) && (counter <= 21)) ? 255 : 0);

void setPixel(int pixelNumber, int red)
{
  strip.setPixelColor(pixelNumber, red, 0, 0);
  strip.show();
}

However, the conditions can be simplified by adding them into the function. So we get

// NeoPixel Display   
setPixel(0, counter,  3,  9);
setPixel(1, counter, 10, 15);
setPixel(2, counter, 16, 21);

void setPixel(int pixelNumber, int counter, int lowValue, int highValue)
{
  strip.setPixelColor(pixelNumber, 
     ((counter >= lowValue) && (counter <= highValue)) ? 255 : 0, 
     0, 0);
  strip.show();
}

If you need to have more checks if a value is in range you can make it a specific function. This will increase the code, but makes it easier to reuse code. So you will get:

// NeoPixel Display   
setPixel(0, counter,  3,  9);
setPixel(1, counter, 10, 15);
setPixel(2, counter, 16, 21);

void setPixel(int pixelNumber, int counter, int lowValue, int highValue)
{
  strip.setPixelColor(pixelNumber, 
    inRange(counter, lowValue, highValue) ? 255 : 0,
     0, 0);
  strip.show();
}

int inRange(int counter, int lowValue, int highValue)
{
   return ((counter >= lowValue) && (counter <= highValue));
}

Thanks for the great help, I learned a lot on this. Now onto the Roary Encoder that will feed the NeoPixel ring. — Bkukuk62, Sep 22 '18 at 19:13
Good luck with the project, glad to heard you learnt something (I still do daily too here). — Michel Keijzers, Sep 22 '18 at 20:01
I'd vote this answer up twice if I could! Good job! Loving the use of the ternary operator and the iterative approach to building up the program. — linhartr22, Sep 28 '18 at 01:34

Simplify if then else statements for Neopixel/compass project

1 Answers1