[example] Add Nucleo G474RE DAC DMA example

examples/nucleo_g474re/dac_dma/main.cpp

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+/*
+ * Copyright (c) 2021, Christopher Durand
+ *
+ * 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 <numbers>
+#include <cmath>
+#include <array>
+
+using namespace Board;
+
+constexpr auto computeSinTable(float frequency = 1.f)
+{
+	std::array<uint16_t, 100> data{};
+	constexpr auto HalfOutput = ((1 << 12) - 1) / 2; // 12 bit dac
+	for (size_t i = 0; i < data.size(); ++i) {
+		constexpr auto pi = std::numbers::pi_v<float>;
+		data[i] = HalfOutput * (1 + sin(i * (2 * pi * frequency / data.size())));
+	}
+	return data;
+}
+
+constexpr auto sinTable1 = computeSinTable(1.0f);
+constexpr auto sinTable2 = computeSinTable(2.0f);
+
+// DAC1 channel 1 on GpioA4: constantly output 20kHz sine signal in circular mode
+// DAC4 channel 1 on GpioB12: switch between 20kHz and 40 kHz sine signal after DMA transfer complete
+
+void setupDac1()
+{
+	using Dac = Dac1Dma;
+	using DacChannel = Dac::Channel1<Dma1::Channel1>;
+
+	Dac::connect<GpioOutputA4::Out1>();
+	Dac::initialize<Board::SystemClock>();
+
+	DacChannel::configure(sinTable1.data(), sinTable1.size(), DmaBase::CircularMode::Enabled);
+
+	// trigger source 5: timer 4 for DAC4, see reference manual
+	DacChannel::setTriggerSource(5);
+
+	DacChannel::startDma();
+	DacChannel::enableDacChannel();
+}
+
+void setupDac4()
+{
+	using Dac = Dac4Dma;
+	using DacChannel = Dac::Channel1<Dma1::Channel2>;
+
+	Dac::initialize<Board::SystemClock>();
+
+	// Internal output to opamp 4
+	DacChannel::setMode(DacChannel::Mode::Internal);
+
+	DacChannel::configure(sinTable1.data(), sinTable1.size(), DmaBase::CircularMode::Disabled);
+
+	// trigger source 5: timer 4 for DAC4, see reference manual
+	DacChannel::setTriggerSource(5);
+
+	// switch between signals when transfer completed
+	static bool toggleBit = false;
+	Dma1::Channel1::setTransferCompleteIrqHandler([]() {
+		DacChannel::stopDma();
+		toggleBit = !toggleBit;
+		if (toggleBit) {
+			DacChannel::setData(sinTable1.data(), sinTable1.size());
+		} else {
+			DacChannel::setData(sinTable2.data(), sinTable2.size());
+		}
+		DacChannel::startDma();
+	});
+
+	Dma1::Channel1::enableInterruptVector();
+	Dma1::Channel1::enableInterrupt(Dma1::Interrupt::TransferComplete | Dma1::Interrupt::Error);
+
+	// DAC4 channel 1 output via opamp 4 in follower mode connected to output B12
+	GpioOutputB12::setAnalogInput();
+	OPAMP4->CSR = OPAMP_CSR_OPAMPxEN | OPAMP_CSR_VPSEL | OPAMP_CSR_VMSEL;
+
+	DacChannel::startDma();
+	DacChannel::enableDacChannel();
+}
+
+int main()
+{
+	Board::initialize();
+	LedD13::setOutput();
+
+	MODM_LOG_INFO << "DAC DMA Demo" << modm::endl;
+
+	Dma1::enable();
+
+	setupDac1();
+	setupDac4();
+
+	// configure timer 4 as trigger for DACs
+	// 170 MHz / 85 = 2 MHz => 2 Msps DAC output
+	Timer4::enable();
+	Timer4::setMode(Timer4::Mode::UpCounter);
+	Timer4::setPrescaler(1);
+	Timer4::setOverflow(85 - 1);
+	Timer4::applyAndReset();
+	Timer4::start();
+
+	// Enable trigger out for timer 4
+	TIM4->CR2 |= TIM_CR2_MMS_1;
+
+	while (true)
+	{
+		LedD13::toggle();
+		modm::delay_ms(500);
+	}
+
+	return 0;
+}

examples/nucleo_g474re/dac_dma/project.xml

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+<library>
+  <extends>modm:nucleo-g474re</extends>
+  <options>
+    <option name="modm:build:build.path">../../../build/nucleo_g474re/dac_dma</option>
+  </options>
+  <modules>
+    <module>modm:debug</module>
+    <module>modm:platform:dac:1</module>
+    <module>modm:platform:dac:4</module>
+    <module>modm:platform:dma</module>
+    <module>modm:platform:timer:4</module>
+    <module>modm:build:scons</module>
+  </modules>
+</library>