Questions about DMX512 protocol/STM
DMX transmitters are superficially easy, but there are a number of traps if you want your kit to play nice with at least most of the really trashy end of the DMX receiver market....

In particular if you stick to max rate (especially max rate on minimum channel count, ~1.2ms per packet) you will find a lot of cheap shit that does not correctly decode it (Cheap LED cans, looking at you). Even a full 512 channel packet running at max rate can cause problems with the "Third tier" kit, which is why grown up lighting desks usually have a way to diddle the DMX timings to something slightly more conservative. 

Another nice trap is moving lights that do interpolation, these really need your movement calculations to be synchronous with the DMX frame timing, to minimise jitter, doing the sums at 100Hz when the transmitter is getting ~40 frames a second on the wire does NOT work well.  

The real timing pain is in the receivers, especially in a receiver on a minimal cost micro, on the transmitter side, just be very conservative in what you generate (and give the operator the option to slow things down if necessary).