Toggling DMA PWM channels

Official Hardware Classic Zero
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Thanks to help from MartinL in (upload://znp3jHgReu79IVfTgBKx145uEsP.jpeg) this thread https://forum.arduino.cc/t/ideas-for-pwm-with-repeating-pattern/847923/2 , I've been able to generate PWM sine waveforms on two pins using two DMA channels and timer/counters TCC0 on one pin and TCC1 on the other.

Each channel reads the same sine lookup table. Since I want 1/2 cycle on each channel, the second half of the lookup table is all zeros, and I preset TCC1 to generate a 180 degree phase difference. The attached pic shows the result (sorry for the quality and jpg format; this scope is too old to have a USB port).

Now that the hard part is done, I'm looking for ideas to implement the last couple of issues. Specifically, I have two questions:

  1. Is there a way to ensure that the two channels are exactly 180 degrees out of phase (ie, no overlap in their waveforms)?

  2. What is the best way to stop and start both channels simultaneously -- I need to trigger the pair on and off via an external signal (a digital input on another GPIO pin)?

Thanks!

spwm_scope
spwm_scope1024×752 399 KB

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