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nevercast opened this issue Oct 16, 2019 · 10 comments
Open

ESP32 Pulse Counter Driver #5216

nevercast opened this issue Oct 16, 2019 · 10 comments
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port-esp32

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@nevercast
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Add a driver for ESP32 Pulse Counter Hardware.

Related to: #5214
@tve
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tve commented Jan 5, 2020

I want to implement this. Is there an API I should copy?

@nevercast
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I don't know that any other devices have a "Pulse counter" in any sense, other than using just a hardware counter driven by a pin. I also have not seen a Python implementation for one.

Other than a constructor that takes a Pin object, and a function that gets the counts, everything else might be device specific. Since this issue is ESP32 specific, perhaps go with something that is a close mapping to https://docs.espressif.com/projects/esp-idf/en/v3.3/api-reference/peripherals/pcnt.html in the same way that the RMT implementation closely matches the ESP IDF implementation.

For now, I'd say, implement it under the esp32 namespace. from esp32 import PCNT, and we can discuss the API and make it more generic in the future.

It's generally understood by the community that I've interfaced with that classes under the device specific namespaces are far more likely to change than something under machine for example. So start with the device specific implementation so that we have something to discuss and we can go from there.

Thanks for offering your time to improve MicroPython ❤️ 🐍

@tve
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tve commented Jan 7, 2020

Thanks for the comment. Please see #5496
There is nothing esp32-specific in there and it is one abstraction on top of a generic timer that exposes one set of use-cases. There's also a link there to a thread on slack discussing it.

@sengpw
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sengpw commented Jan 27, 2020 •
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I want to implement this. Is there an API I should copy?

Seems it is already implemented:
from machine import DEC

See:
https://people.eecs.berkeley.edu/~boser/courses/49_sp_2019/N_gpio.html#_quadrature_decoder

Sources seem to be here:
https://github.com/bboser/MicroPython_ESP32_psRAM_LoBo/commit/15806f44ad565e77967da57d67ad068001f44e28

But have no idea how to upstream this to micropython 1.12.

Any ideas?

Best regards,

Peter

@tve
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tve commented Jan 27, 2020

Use #5496?

@sengpw
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sengpw commented Jan 28, 2020

Use #5496?

I'm not shure about it, may be it's related to (see above):

Add a driver for ESP32 Pulse Counter Hardware.

Related to: #5214

Already made some efforts, could integrate the code into lv-micropython V1.12. --> Test run OK. Must verify it on real hardware. But quadrature - decoder interface including counter based on ESP32 hardware seems to be already done. I'll notice when finished.

best regards
Peter

@tve tve mentioned this issue Feb 14, 2020
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@tve tve mentioned this issue Feb 23, 2020
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@mattytrentini
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The CircuitPython countio implementation is simple and neat; may be a good starting point for reference. (I see it's effectively a subset of yours, @tve).

@tve
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tve commented Jun 5, 2020

I believe this is best implemented as dynamically loadable driver. This way it's easy to change things around. I did that: https://github.com/tve/mpy-lib/tree/master/esp32-counter. Of course that relies on #5711 but perhaps that gets reviewed someday and maybe even merged if the stars align...

@jonathanhogg
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I have need of the pulse counter in a current ESP32 project and, not seeing any maintained implementations, have gone ahead and rolled another. Sorry.

Since there doesn't seem to be much movement on the idea of exposing the IDF functions through dynamic linking, I've just added it as a straight-C extension of the machine module in the ESP32 port. I started copying your API from #5496, @tve, but then took a slightly different tack when I realised that I couldn't figure out how to support all of the features of the ESP32 PCNT peripheral with it.

So I have gone for this in the simple case:

from machine import Counter, Pin

counter = Counter(0, pin=Pin(12, Pin.IN), rising=Counter.INCREMENT)
counter.start()
count = counter.value()

This looks like it ought to work OK as an API for other ports. However, using rising= and falling= instead of edge= allows for both to be specified, which means the extended functionality of the ESP32 PCNT peripheral can be used to do easy 1X decoding of a quadrature rotary encoder:

from machine import Counter, Pin

pin_a = Pin(12, Pin.IN, pull=Pin.PULL_UP)
pin_b = Pin(14, Pin.IN, pull=Pin.PULL_UP)
counter = Counter(0, pin=pin_a, rising=Counter.DECREMENT, falling=Counter.INCREMENT,
                     mode_pin=pin_b, mode_high=Counter.NORMAL, mode_low=Counter.HOLD)
counter.start()
count = counter.value()

Or use mode_low=Counter.REVERSE to do 2X decoding. In fact, this implementation also supports calling the .init() method with an additional channel=1 keyword argument to configure the second channel of the PCNT, allowing for 4X decoding on a single PCNT unit.

It also supports filter= to set the short pulse filter, minimum= and maximum= for setting counter limits, threshold0= and threshold1= for setting threshold event levels and all of the PCNT events (IRQ_ZERO, IRQ_MINIMUM, IRQ_MAXIMUM, IRQ_THRESHOLD0 and IRQ_THRESHOLD1) via the .irq(trigger=, handler=) method.

I've not written any documentation for it yet I'm afraid. It's sitting in draft PR #7582 if anyone is interested in looking at it. Like I say, my primary reason for doing this is that I need it more than that I'm interested in seeing it through to mainline. I don't have any hardware for the other MicroPython architectures to work on an implementation of Counter for them.

@jonathanhogg jonathanhogg mentioned this issue Jul 26, 2021
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@IhorNehrutsa
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docs\machine: Add Counter and Encoder classes. #8072
ESP32: New hardware PCNT Counter() and Encoder(). #6639

@jonathanhogg jonathanhogg mentioned this issue Jan 23, 2022
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