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();

Answer 1

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));
}

• Bkukuk62: Thanks for the great help, I learned a lot on this. Now onto the Roary Encoder that will feed the NeoPixel ring.
• Michel Keijzers: Good luck with the project, glad to heard you learnt something (I still do daily too here).
• linhartr22: 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.