[example] Nucleo-G474RE: Servo PWM example

Author: rleh

examples/nucleo_g474re/servo_pwm/main.cpp

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+/*
+ * Copyright (c) 2021, Raphael Lehmann
+ *
+ * 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>
+
+using namespace Board;
+
+int
+main()
+{
+	Board::initialize();
+	LedD13::setOutput();
+
+	MODM_LOG_INFO << "modm example: Servo PWM" << modm::endl << modm::endl;
+	MODM_LOG_INFO << "Generates a 50 Hz PWM signal with a pulse width between 1 ms and 2 ms suitable" << modm::endl;
+	MODM_LOG_INFO << "for many servo motors or RC electronic speed controllers on pin B7." << modm::endl;
+	MODM_LOG_INFO << "1.5 ms pulse width is output when the user button is pressed, " << modm::endl;
+	MODM_LOG_INFO << "otherwise 1 ms pulse width." << modm::endl << modm::endl;
+
+	Timer4::connect<GpioB7::Ch2>();
+	Timer4::enable();
+	Timer4::setMode(Timer4::Mode::UpCounter);
+
+	constexpr uint16_t overflow = 0xffff;
+	constexpr uint16_t minPwm = (overflow / 20.f) * 1.f; // 1 ms pulse width
+	constexpr uint16_t targetPwm = (overflow / 20.f) * 1.5f; // 1.5 ms pulse width
+	constexpr uint16_t maxPwm = (overflow / 20.f) * 2.f; // 2 ms pulse width
+
+	// 170 MHz / 52 / 2^16 = approx. 50 Hz
+	Timer4::setPrescaler(52);
+	Timer4::setOverflow(overflow);
+
+	Timer4::configureOutputChannel(2, Timer4::OutputCompareMode::Pwm, 0);
+
+	Timer4::applyAndReset();
+
+	Timer4::start();
+	Timer4::enableOutput();
+
+	MODM_LOG_INFO << "Teaching sequence for electronic speed controllers:" << modm::endl;
+	MODM_LOG_INFO << "1.0 ms pulse width for 2 s" << modm::endl;
+	MODM_LOG_INFO << "2.0 ms pulse width for 2 s" << modm::endl;
+	MODM_LOG_INFO << "1.0 ms pulse width for 1 s" << modm::endl;
+	LedD13::set();
+	Timer4::configureOutputChannel(2, Timer4::OutputCompareMode::Pwm, minPwm);
+	modm::delay(2000ms);
+	Timer4::configureOutputChannel(2, Timer4::OutputCompareMode::Pwm, maxPwm);
+	modm::delay(2000ms);
+	Timer4::configureOutputChannel(2, Timer4::OutputCompareMode::Pwm, minPwm);
+	LedD13::reset();
+	modm::delay(1000ms);
+
+	MODM_LOG_INFO << modm::endl;
+
+	while (true)
+	{
+		LedD13::toggle();
+		modm::delay(100ms);
+
+		if (!Button::read()) {
+			Timer4::setCompareValue(2, targetPwm);
+			MODM_LOG_INFO << "^";
+		}
+		else {
+			Timer4::setCompareValue(2, minPwm);
+			MODM_LOG_INFO << "-";
+		}
+	}
+
+	return 0;
+}

examples/nucleo_g474re/servo_pwm/project.xml

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+<library>
+  <extends>modm:nucleo-g474re</extends>
+  <options>
+    <option name="modm:build:build.path">../../../build/nucleo_g474re/servo_pwm</option>
+  </options>
+  <modules>
+    <module>modm:build:scons</module>
+    <module>modm:platform:timer:4</module>
+  </modules>
+</library>