Dim LED over time in a even flow using Arduino - arduino

Question

Im trying to figure out how to dim a led over time(time is defined by the user lets call it rampUp). Im using arduino with the adafruit breakout PWM-Servo-Driver (http://www.adafruit.com/products/815) with the library : https://github.com/adafruit/Adafruit-PWM-Servo-Driver-Library
this breakout has 4095 steps (0-4095) so now my problem:
I want to be able to take a variable ( int minutes) and send that to a method that will dim a LED from 0 to 4095 in a equal light intensity increase for the period minutes. I want the increase to be incremented by 1 each time it increases.
So how do I write the method without using delay() ?
void dimLights(int rampUp){
// some code to regulate the increase of the third value in setPWM one step at a time over a period of rampUp(int in minutes)
led.setPWM(0,0,4095);
}
the reason for not wanting to use delay() is because it will pause/stop the rest of the program.

Answer 1

I actually implemented something close recently:
void loop() {
/* ... */
if (rampUp != 0)
led.setPWM(0,0,rampUp);
}
void led_update() {
// here you can prescale even more by using something like
// if (++global_led_idx == limit) {
// global_led_idx = 0;
++rampUp;
}
void start() {
TCCR1B |= _BV(WGM12);
// set up timer with prescaler = FCPU/1024 = 16MHz/1024 ⇒ 60ms
TCCR1B |= _BV(CS12) | _BV(CS10);
TCCR1B &= ~_BV(CS11);
// initialize counter
OCR1A = 0x0000;
// enable global interrupts
sei();
// enable overflow interrupt
TIMSK1 |= _BV(OCIE1A);
}
void TAGByKO_LED::stop() {
TIMSK1 &= ~_BV(OCIE1A);
rampUp = 0;
}
ISR(TIMER1_COMPA_vect, ISR_NOBLOCK) {
led_update();
}
then you can call start() to start the timer, or stop() to stop it. You can read more documentation about the registers I've been using here and the ISR statement. Beware that it's one of the most tricky things of AVRs to really understand, and even then you'll always need to have a cheatsheet or the datasheet close by.
You may also use #sr-richie's solution with timers, but do only setup variables in the dimLights() function, and call led.setPWM() only within the loop().