This evening I've also created another 2 functions for controlling an RGB LED. The first function holds an LED at a certain RGB value for a given time period, using PWM, nothing special there. The second function accepts 2 RGB values, then fades between them over a given time period, with a smooth gradient. One can now program a lighting sequence using the simple colour "holds" and "fades".
My problem with the fade code is that I could only seem to make it work when using floating point arithmetic. Attempting to mix up integer math made the PWM go all wrong. So the Arduino is performing a LOT more operations that it really should be doing. This does not affect the timing of the LED colour-changes (to my eyes at least) though I havn't done any rigorous sort of test on that:
//i/o pin declarations
int rpin = 9;
int gpin = 10;
int bpin = 11;
//function prototypes
void solid(int r, int g, int b, int t);
void fade(int r1, int g1, int b1, int r2, int g2, int b2, int t);
void setup()
{
//empty
}
void loop()
{
//colour sequence instructions
//Example sequence one: Rainbow fade over 15 seconds:
fade(255,0,0,0,255,0,5000); //fade from red to green over 5 seconds
fade(0,255,0,0,0,255,5000); //fade from green to blue over 5 seconds
fade(0,0,255,255,0,0,5000); //fade from blue to red over 5 seconds
}
//function holds RGB values for time t milliseconds
void solid(int r, int g, int b, int t)
{
//map values - arduino is sinking current, not sourcing it
r = map(r, 0, 255, 255, 0);
g = map(g, 0, 255, 255, 0);
b = map(b, 0, 255, 255, 0);
//output
analogWrite(rpin,r);
analogWrite(gpin,g);
analogWrite(bpin,b);
//hold at this colour set for t ms
delay(t);
}
//function fades between two RGB values over fade time period t
//maximum value of fade time = 30 seconds before gradient values
//get too small for floating point math to work? replace floats
//with doubles to remedy this?
void fade(int r1, int g1, int b1, int r2, int g2, int b2, int t)
{
float r_float1, g_float1, b_float1;
float r_float2, g_float2, b_float2;
float grad_r, grad_g, grad_b;
float output_r, output_g, output_b;
//declare integer RGB values as float values
r_float1 = (float) r1;
g_float1 = (float) g1;
b_float1 = (float) b1;
r_float2 = (float) r2;
g_float2 = (float) g2;
b_float2 = (float) b2;
//calculate rates of change of R, G, and B values
grad_r = (r_float2-r_float1)/t;
grad_g = (g_float2-g_float1)/t;
grad_b = (b_float2-b_float1)/t;
//loop round, incrementing time value "i"
for ( float i=0; i<=t; i++ )
{
output_r = r_float1 + grad_r*i;
output_g = g_float1 + grad_g*i;
output_b = b_float1 + grad_b*i;
//map values - arduino is sinking current, not sourcing it
output_r = map (output_r,0,255,255,0);
output_g = map (output_g,0,255,255,0);
output_b = map (output_b,0,255,255,0);
//output
analogWrite(rpin, (int)output_r);
analogWrite(gpin, (int)output_g);
analogWrite(bpin, (int)output_b);
//hold at this colour set for 1ms
delay(1);
}
}