HSI to RGB / RGBW with optional PWM output¶

Library for converting HSI color space values to RGB or RGBW and, optionally, directly send the converted values to PWM outputs.

Code ported from http://saikoled.com - Copyright 2013, Brian Neltner
http://blog.saikoled.com/post/44677718712/how-to-convert-from-hsi-to-rgb-white

Info on the HSI color space can be found here and here.

Demo code using the KL25Z-FRDM board:

Constructor & conversion function
depending on the way you want to use this library, you can call the conversion function in different ways

// Assign 4 PWM outputs and also allow to return the converted RGBW value.
hsi2rgbw_pwm led(PTD4, PTA12, PTA4, PTA5);
// Call to the conversion function
float H, S, I;
float rgbw[4];
led.hsi2rgbw(H, S, I, rgbw);

// Assign 4 PWM outputs, no converted RGBW value will be returned.
hsi2rgbw_pwm led(PTD4, PTA12, PTA4, PTA5);
// Call to the conversion function
float H, S, I;
led.hsi2rgbw(H, S, I);

// No PWM outputs are assigned, only the converted RGBW value will be returned.
hsi2rgbw_pwm led;
// Call to the conversion function
float H, S, I;
float rgbw[4];
led.hsi2rgbw(H, S, I, rgbw);

// Assign 3 PWM outputs and also allow to return the converted RGB value.
hsi2rgbw_pwm led(PTD4, PTA12, PTA4);
// Call to the conversion function
float H, S, I;
float rgb[4];
led.hsi2rgbw(H, S, I, rgbw);

// Assign 3 PWM outputs, no converted RGB value will be returned.
hsi2rgbw_pwm led(PTD4, PTA12, PTA4);
// Call to the conversion function
float H, S, I;
led.hsi2rgbw(H, S, I);

// No PWM outputs are assigned, only the converted RGB value will be returned.
hsi2rgbw_pwm led;
// Call to the conversion function
float H, S, I;
float rgb[4];
led.hsi2rgbw(H, S, I, rgb);

Hue, Saturation and Intesity range

RGB(W) return value
In your main program, declare an array of 4 float values and pass the pointer to this array to the function:
Even when RGB is used, do declare an array of 4 float values.

float rgbw[4];

Upon exit, the function will return the values in rgbw[], representing the red, green, blue and white component that corresponds to the chosen HSI values. Range : 0...1 where 0 = minimum and 1 = maximum.

parabolic mode
By default, each component of the RGB(W) return value is mapped to a parabolic scale.
Call led.parabolic(0); to disable the parabolic mapping.

Choose RGB or RGBW mode
By default, the conversion return value is set to RGBW.
Call led.colorMode(RGB); to change to RGB mode.
Call led.colorMode(RGBW); to go back to RGBW mode.

Change PWM period
By default, the PWM period is set to 4ms (250Hz).
Call led.period(n); to change the PWM period (replace n with a value in ms).

Change PWM values
We can alter the PWM outputs directly, without passing through the HSI to RGB(W) conversion.
declare float rgbw[4]; and set each value of this array.
Call led.pwm(rgbw); to write the values directly to the PWM outputs.

NOTES
period() and pwm() will not change any value if no PWM pins are declared.
Do not forget to replace led. with the declared function name.