Interrupt / Timer advice: Driving LED matrix while reading serial data

Projects Programming
3

My current code looks like this:

static const int ISR_STEPS = 14;
static int currentIsrStep = 0;

ISR(TIMER1_OVF_vect) {
  switch (currentIsrStep) {
    case 0:
      // do first part of the LED matrix update code
      break;
    case 1:
      // second part of the LED matrix update code
      break;
    [...]
    case 9:
      ...
      break;
    case 10:
      ...
      break;
  }
  currentIsrStep++;
  if (currentIsrStep == ISR_STEPS) {
    currentIsrStep = 0;
  }
}

Steps 0-10 are each calling parts of the code needed to update the LED matrix - steps 11-13 are doing nothing so that the entire update code is running as close as possible at the beginning of my original ~1250us interval.

Instead of having a fixed interrupt call rate I'd like to set at the end of every interrupt method call the duration until the TIMER1 will again call the interrupt method. If I would be able to query somehow if the serial interrupt has to do some work than this would be a plus.

Greetings,
Markus