[examples] Add BitBangEncoderInput example on AVR

examples/arduino_nano/encoder_input/main.cpp

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+/*
+ * 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/.
+ */
+// ----------------------------------------------------------------------------
+
+#include <modm/board.hpp>
+#include <modm/driver/encoder/bitbang_encoder_input.hpp>
+#include <modm/math/algorithm/prescaler.hpp>
+#include <modm/processing/timer.hpp>
+
+using namespace modm::platform;
+
+// 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;
+
+MODM_ISR(TIMER2_COMPA)
+{
+	encoder.update();
+}
+
+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");
+
+	// Timer in CTC Mode
+	TCCR2A = (1 << WGM21);
+	OCR2A = ocr;
+	TIMSK2 |= (1 << OCIE2A);
+	TCCR2B |= prescaler.index;
+}
+
+int
+main()
+{
+	Board::initialize();
+	LedD13::setOutput();
+
+	encoder.connect();
+
+	init_Timer2();
+	enableInterrupts();
+
+	int value(0);
+
+	modm::ShortPeriodicTimer heartbeat(500ms);
+	modm::ShortPeriodicTimer outputValue(1000ms);
+
+	while (true)
+	{
+		if (heartbeat.execute()) Board::LedD13::toggle();
+		if (outputValue.execute())
+		{
+			value += encoder.getIncrement();
+			MODM_LOG_INFO << "value: " << value << modm::endl;
+		}
+	}
+}

examples/arduino_nano/encoder_input/project.xml

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+<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>