Random Errors

Posted: March 6, 2025 | Categories: IoT

I'm doing some Arduino development for a friend, helping him build a throttle gauge for his race car. For this project I have a string of NeoPixels and I'm trying to figure out how many of them to illuminate based on the car's throttle position. Whenever I calculate the value, the result is always zero. Here's the code:

#define NUM_LEDS 7
const int divisor = 4095;   // for ESP32 devices
int numIlluminatedPixels;
int throttleValue;

numIlluminatedPixels = (throttleValue / divisor) * NUM_LEDS;

The result of throttleValue / divisor is always a fraction and multiplying that result by an integer results in a float. Assigning the result to an integer truncates the value into an Integer (int) which is exactly what I want.

Nope, every time I get a zero, even if I break it out into multiple calculations.

The solution is that I have to force (cast) my division operands to float values, then it works perfectly.

#define NUM_LEDS 7
const int divisor = 4095;   // for ESP32 devices
int throttleValue;
int numIlluminatedPixels;

numIlluminatedPixels = ((float)throttleValue / (float)divisor) * NUM_LEDS;