I count cycles to output timecode (SMPTE 12M).
Other manufacturers have crystals of exactly 0.2ppm. This allows for drift of no more than 1 frame per day.

With the current crystal of 10ppm, the drift is too large. Therefore, I need to count as accurately as possible. Since I use timers, I am ...

I use hardware timers

bitTimer = timerBegin(0, 2, true);
timerAttachInterrupt(bitTimer, &timerESP, true);
timerAlarmWrite(bitTimer, halfBit, true);
timerAlarmEnable(bitTimer);

My board uses a 40 MHz 10ppm crystal, I want to improve the accuracy of the timer. From the documentation I ...