I have an Arduino Giga (STM32H7) and I'm using the timers to generate PWM's. Everything's working fine, programming is no problem, but I cannot come up with a way to implement what I want. I included a simple visual to describe what I want the output to look like.
TIM1 is the master timer, it generates a PWM, set as active high (for CNT<CCR). I have a slave TIM8, which should do the following: when TIM1 starts over again/goes high, TIM8 should generate N pulses. The time it takes for N pulses to complete is shorter than the period of TIM1, I want them to retrigger each time TIM1 goes high again. Here's the catch: The pulses should immediately start high, however, once all the pulses have fired, the output should stay low.
If it weren't for the last part, the solution would be simple: TIM1 uses UEV as output trigger, TIM8 takes an internal trigger input from TIM1, set TIM8 to One-Pulse Mode, set the repetition counter to N, and voila, you get bursts of N pulses on each TIM1 high (yes technically the first time it won't trigger, doesn't matter).
However, this will cause the pulses of TIM8 to either start 'delayed', since for CNT<CCR, the output will be low in OPM, or if we flip the polarity, it will start high, but after having finished N pulses, TIM8->CNT=0 (because of OPM), which causes the output to be high...
Can anyone think of a good solution/setup? Again, programming is no issue, it's just finding a way to get this behaviour, if that's even possible... Also, I would prefer not to use interrupts handlers for reasons related to the rest of my program.
1 ACCEPTED SOLUTION
Accepted Solutions
Very doable with a number of methods
Perhaps the easiest is to use the scheme that almost works except use PWM mode 2 and set it so output is low at CNT=0, high at CNT=1... X, and then low again until it reaches ARR.
If you need them to exactly match, you could use TIM8 in gated slave mode to get exactly 4 pulses at the start of each TIM1 period. Can describe this more if you need.
Very doable with a number of methods
Perhaps the easiest is to use the scheme that almost works except use PWM mode 2 and set it so output is low at CNT=0, high at CNT=1... X, and then low again until it reaches ARR.
If you need them to exactly match, you could use TIM8 in gated slave mode to get exactly 4 pulses at the start of each TIM1 period. Can describe this more if you need.
