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[driver] Add best practice driver for soft graycode / quadrature decoding #580
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,70 @@ | ||
| /* | ||
| * Copyright (c) 2021, Thomas Sommer | ||
| * | ||
| * This file is part of the modm project. | ||
| * | ||
| * This Source Code Form is subject to the terms of the Mozilla Public | ||
| * License, v. 2.0. If a copy of the MPL was not distributed with this | ||
| * file, You can obtain one at http://mozilla.org/MPL/2.0/. | ||
| */ | ||
| // ---------------------------------------------------------------------------- | ||
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| #include <modm/board.hpp> | ||
| #include <modm/driver/encoder/bitbang_encoder_input.hpp> | ||
| #include <modm/math/algorithm/prescaler.hpp> | ||
| #include <modm/processing/timer.hpp> | ||
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| using namespace modm::platform; | ||
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| // Connect the encoders outputs to D7 and D8 Pins (usually the outer pins) | ||
| // The common third pin (usually in the middle) is connected to GND. | ||
| // Don't add any resistors or filters. It's all in the MCU and the driver. | ||
| modm::BitBangEncoderInput<Board::D11, Board::D12, 4> encoder; | ||
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| MODM_ISR(TIMER2_COMPA) | ||
| { | ||
| encoder.update(); | ||
| } | ||
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| void | ||
| init_Timer2() | ||
| { | ||
| constexpr float f = 1_kHz; | ||
| constexpr auto prescaler = | ||
| modm::Prescaler::from_list(SystemClock::Timer, f * 2, {0, 1, 8, 32, 64, 128, 256, 1024}); | ||
| constexpr auto ocr = (prescaler.frequency / f) - 1; | ||
| static_assert(ocr <= 255, "Can't configure Timer2 for desired f"); | ||
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| // Timer in CTC Mode | ||
| TCCR2A = (1 << WGM21); | ||
| OCR2A = ocr; | ||
| TIMSK2 |= (1 << OCIE2A); | ||
| TCCR2B |= prescaler.index; | ||
| } | ||
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| int | ||
| main() | ||
| { | ||
| Board::initialize(); | ||
| LedD13::setOutput(); | ||
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| encoder.connect(); | ||
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| init_Timer2(); | ||
| enableInterrupts(); | ||
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| int value(0); | ||
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| modm::ShortPeriodicTimer heartbeat(500ms); | ||
| modm::ShortPeriodicTimer outputValue(1000ms); | ||
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| while (true) | ||
| { | ||
| if (heartbeat.execute()) Board::LedD13::toggle(); | ||
| if (outputValue.execute()) | ||
| { | ||
| value += encoder.getIncrement(); | ||
| MODM_LOG_INFO << "value: " << value << modm::endl; | ||
| } | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,11 @@ | ||
| <library> | ||
| <extends>modm:arduino-nano</extends> | ||
| <options> | ||
| <option name="modm:build:build.path">../../../build/arduino_nano/encoder_input</option> | ||
| </options> | ||
| <modules> | ||
| <module>modm:build:scons</module> | ||
| <module>modm:processing:timer</module> | ||
| <module>modm:driver:encoder_input.bitbang</module> | ||
| </modules> | ||
| </library> |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,72 @@ | ||
| /* | ||
| * Copyright (c) 2021, Thomas Sommer | ||
| * | ||
| * This file is part of the modm project. | ||
| * | ||
| * This Source Code Form is subject to the terms of the Mozilla Public | ||
| * License, v. 2.0. If a copy of the MPL was not distributed with this | ||
| * file, You can obtain one at http://mozilla.org/MPL/2.0/. | ||
| */ | ||
| // ---------------------------------------------------------------------------- | ||
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| #ifndef MODM_BITBANG_ENCODER_INPUT_HPP | ||
| #define MODM_BITBANG_ENCODER_INPUT_HPP | ||
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| #include <bit> | ||
| #include <modm/platform.hpp> | ||
| #include <type_traits> | ||
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| namespace modm | ||
| { | ||
| /** | ||
| * @ingroup modm_driver_bitbang_encoder_input | ||
| * @author Thomas Sommer | ||
| * | ||
| * @brief This driver decodes a AB (incremental) encoder signal | ||
| * | ||
| * @tparam SignalA First modm::platform::Gpio pin to input the encoder signal. | ||
| * @tparam SignalB Second modm::platform::Gpio pin to input the encoder signal. | ||
| * @tparam POSTSCALER n_cycles to count as one in-/decrement. | ||
| * @tparam DeltaType Must be signed integer and fit at least POSTSCALER. The Bigger | ||
| * DeltaType, the more inc-/decrements can be stored temporarily. | ||
| */ | ||
| template<typename SignalA, typename SignalB, uint8_t POSTSCALER = 4, | ||
| std::signed_integral DeltaType = int8_t> | ||
| class BitBangEncoderInput | ||
| { | ||
| static_assert(std::popcount(POSTSCALER) == 1, | ||
| "POSTSCALER must be an integer to basis 2 and not 0: 1, 2, 4, 8, 16, ..."); | ||
| static_assert(POSTSCALER <= std::numeric_limits<DeltaType>::max(), | ||
| "DeltaType is to small for POSTSCALER."); | ||
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| using Signals = modm::platform::SoftwareGpioPort<SignalA, SignalB>; | ||
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| static_assert(Signals::number_of_ports == 1, | ||
| "Signal A/B must be on the same GPIO port to prevent signal tearing!"); | ||
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| uint8_t inline getRaw(); | ||
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| public: | ||
| using ValueType = DeltaType; | ||
| BitBangEncoderInput() : raw_last(0), delta(0){}; | ||
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| // Connect SingalA and SignalB and store power-up state | ||
| inline void | ||
| connect(); | ||
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| // Call @1kHz for manual movement | ||
| inline void | ||
| update(); | ||
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| ValueType | ||
| getIncrement(); | ||
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| private: | ||
| uint8_t raw_last; | ||
| DeltaType delta; | ||
| }; | ||
| } // namespace modm | ||
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| #include "bitbang_encoder_input_impl.hpp" | ||
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| #endif // MODM_BITBANG_ENCODER_INPUT_HPP | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,32 @@ | ||
| #!/usr/bin/env python3 | ||
| # -*- coding: utf-8 -*- | ||
| # | ||
| # Copyright (c) 2019, Thomas Sommer | ||
| # | ||
| # This file is part of the modm project. | ||
| # | ||
| # This Source Code Form is subject to the terms of the Mozilla Public | ||
| # License, v. 2.0. If a copy of the MPL was not distributed with this | ||
| # file, You can obtain one at http://mozilla.org/MPL/2.0/. | ||
| # ----------------------------------------------------------------------------- | ||
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| def init(module): | ||
| module.name = ":driver:encoder_input.bitbang" | ||
| module.description = """ | ||
| # Quadrature Encoder Input | ||
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| This driver decodes a AB (incremental) encoder signal. | ||
| Ported from code created by Peter Dannegger: | ||
| https://www.mikrocontroller.net/articles/Drehgeber. | ||
| """ | ||
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| def prepare(module, options): | ||
| module.depends(":architecture:atomic") | ||
| return True | ||
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| def build(env): | ||
| env.outbasepath = "modm/src/modm/driver/encoder" | ||
| env.copy("bitbang_encoder_input.hpp") | ||
| env.copy("bitbang_encoder_input_impl.hpp") |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,58 @@ | ||
| #ifndef MODM_BITBANG_ENCODER_INPUT_IMPL_HPP | ||
| #error "Don't include this file directly, use 'bitbang_encoder_input.hpp' instead!" | ||
| #endif | ||
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| #include <cmath> | ||
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| template<typename SignalA, typename SignalB, uint8_t POSTSCALER, | ||
| std::signed_integral DeltaType> | ||
| inline uint8_t | ||
| modm::BitBangEncoderInput<SignalA, SignalB, POSTSCALER, DeltaType>::getRaw() | ||
| { | ||
| const uint8_t read = Signals::read(); | ||
| // convert graycode to binary | ||
| uint8_t raw = 0; | ||
| if (read & 0b10) raw = 3; | ||
| if (read & 0b01) raw ^= 1; | ||
| return raw; | ||
| } | ||
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| template<typename SignalA, typename SignalB, uint8_t POSTSCALER, | ||
| std::signed_integral DeltaType> | ||
| inline void | ||
| modm::BitBangEncoderInput<SignalA, SignalB, POSTSCALER, DeltaType>::connect() | ||
| { | ||
| Signals::setInput(::Gpio::InputType::PullUp); | ||
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| // Tare power-on state | ||
| modm::delay(10us); | ||
| raw_last = getRaw(); | ||
| } | ||
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| template<typename SignalA, typename SignalB, uint8_t POSTSCALER, | ||
| std::signed_integral DeltaType> | ||
| inline void | ||
| modm::BitBangEncoderInput<SignalA, SignalB, POSTSCALER, DeltaType>::update() | ||
| { | ||
| uint8_t raw = getRaw(); | ||
| const uint8_t diff = raw_last - raw; | ||
| if (diff & 0b01) | ||
| { | ||
| raw_last = raw; | ||
| delta += (diff & 0b10) - 1; // bit 1 = direction (+/-) | ||
| } | ||
| } | ||
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| template<typename SignalA, typename SignalB, uint8_t POSTSCALER, | ||
| std::signed_integral DeltaType> | ||
| DeltaType | ||
| modm::BitBangEncoderInput<SignalA, SignalB, POSTSCALER, DeltaType>::getIncrement() | ||
| { | ||
| ::modm::atomic::Lock _; | ||
| DeltaType val = delta; | ||
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| delta &= (POSTSCALER - 1); // mask out higher bits | ||
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| constexpr uint8_t shift = std::log2(POSTSCALER); // Number of fraction bits | ||
| return val >> shift; // return whats left without fractions | ||
| } |
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Otherwise the atomic read properties may not be true.
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Very nice mechanism.. Damn i ♥ love ♥ the way you've implemented the low level stuff
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I actually think it's just
Phases::number_of_portswithout a function call… I don't even remember the code I wrote.There was a problem hiding this comment.
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Thanks, half of the credit goes to C++17 with the relaxed constexpr rules:
#19 (comment)
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It is and has already been concidered in the last commits ;)
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Thanks for the interresting background!
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What's the magic spell to get these shift maps?
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Here's the full example: https://github.com/modm-io/modm/blob/develop/examples/stm32f469_discovery/ports/main.cpp