[sdiy] Idea - Triangle wave DCO core

[Olivier Gillet]

> I don't agree that this is a *lot* more work for the MCU, Olivier. Perhaps it's more work than leaving a timer running in the background on it's own, but a practical DCO needs a interrupt at the end of the wavecycle anyway.

Why is it so? I haven't built DCOs so I cannot tell, but my impression
is that you can really refresh the timer interval at any time rather
than systematically at each reset. Might depend on which MCU you use,
but double buffering techniques (interval register is latched on timer
reset) or increment/decrement schemes (page 160 here:
http://www.atmel.com/Images/doc8077.pdf) allow that. So you don't
really need to have an interrupt at each timer cycle ; you just need a
2kHz interrupt (or whatever is your modulations rate) to refresh the
counters, and more importantly you don't really have to be super
precise with the timing of those refreshes.

Olivier