Feature: Hardware PWM #568
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…ded tim/channel, and got example ready to test.
litui
reviewed
Mar 23, 2023
| // const int kZeroTime = kTickPeriod - 8; | ||
| const size_t kTickPeriod = 29; | ||
| // const size_t kTickPeriod = 59; | ||
| const int kOneTime = 20; |
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It might make sense here to provide a number of examples alongside different LED controllers. I know there are minor differences between vendors (though mostly it comes out in the wash).
For my example with one of either the WS2812B or SK6812 (unknown which I have on these "neopixel" items), I had MUCH higher reliability with many neopixels (28) setting kOneTime to 14 and kZeroTime to 9, while changing line 114 to chn_cfg.polarity = TimChannel::Config::Polarity::HIGH; (from ::LOW).
I haven't analyzed the waveform yet to determine exactly how the polarity affects things, but my results were VERY unreliable before I set polarity ::HIGH.
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summary
This PR introduces methods of controlling the TIM Channels to do hardware PWM via libDaisy.
This provides typical usage for pins exposed via Daisy Seed, and other official SOMs, as well as DMA control for driving things like Neopixels.
The current API (which I'd like to change) involves:
TimerHandleTimerHandleTimChannelobject with the Channel, mode, polarity, and pin.TimChannelTimChannel::StartPwm, the start the timer withTimerHandle::Start.For normal PWM, you can use the
TimChannel::SetPwmfunction to set the value in real time.For controlling things (like Neopixel LEDs) via DMA it gets a little more complicated.
There are some general improvements to initialization/starting that I feel like could be built into the TimerHandle object instead of being an entire new class.
In addition there's a bit of leftover work to make a more user-friendly driver for neopixels.
This also has the current limitation of only being able to run a single LED strip at a time, without doing some unique sequencing, or making some changes to the implementation.