[example] Add SAMV71 DMA linked list transfer example

Author: chris-durand

examples/samv71_xplained_ultra/dma/linked_list_transfer/main.cpp

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+/*
+ * Copyright (c) 2023, 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 <cmath>
+#include <numbers>
+
+using namespace Board;
+
+/*
+ * DMA linked list transfer example
+ *
+ * Output two alternating signals on DAC output 0
+ */
+
+constexpr auto computeSinTable(float frequency = 1.f)
+{
+	std::array<uint16_t, 50> data{};
+	constexpr auto HalfOutput = Dac::MaxOutput / 2.f;
+	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 std::array<uint16_t, 50> signal0 = computeSinTable(1.0f);
+constexpr std::array<uint16_t, 50> signal1 = computeSinTable(2.0f);
+
+using Out0 = GpioB13;
+
+void initializeDac()
+{
+	Dac::connect<Out0::Ch0>();
+	Dac::initialize<SystemClock, 12_MHz>();
+
+	// Max speed mode: DAC runs at DAC clock / 12 and triggers DMA
+	Dac::setChannelMode(Dac::Channel::Channel0, Dac::Mode::MaxSpeed);
+
+	Dac::enableChannel(Dac::Channel::Channel0);
+}
+
+using ListTransfer = LinkedListTransfer<Dma::View2, Dma::View0Src>;
+
+ListTransfer prepareTransfer()
+{
+	ListTransfer transfer;
+
+	// Transfer configuration, set by first descriptor.
+	// It is not overwritten by the second View0 descriptor.
+	Dma::ChannelConfig_t config;
+	Dma::TransferType_t::set(config, Dma::TransferType::Peripheral);
+	Dma::PeripheralDirection_t::set(config, Dma::PeripheralDirection::MemoryToPeripheral);
+	// 16 bit data size
+	Dma::DataWidth_t::set(config, Dma::DataWidth::HalfWord);
+	// const data in flash, flash is connected to DMA AHB interface 1
+	Dma::SourceBusInterface_t::set(config, Dma::BusInterface::Bus1);
+	// peripherals are connected to DMA AHB interface 1
+	Dma::DestinationBusInterface_t::set(config, Dma::BusInterface::Bus1);
+	// Auto-increment source address after each sample
+	Dma::SourceAddressingMode_t::set(config, Dma::AddressingMode::Incrementing);
+	// Transfer is triggered by DAC channel 0 request
+	Dma::DmaRequest_t::set(config, DmaRequests::Dacc::Ch0Tx);
+
+	auto [d0, d1] = transfer.descriptors();
+
+	// Configure first descriptor (type 2)
+	// Set: configuration, source, destination, size
+	d0.setConfiguration(config);
+	d0.setSourceAddress(signal0.data());
+	d0.setDestinationAddress(Dac::channel0DataRegister());
+	d0.setDataLength(signal0.size());
+
+	// Configure first descriptor (type 0)
+	// Update source and size, other parameters remain unchanged
+	d1.setSourceAddress(signal1.data());
+	d1.setDataLength(signal1.size());
+
+	// Circular mode
+	// After the second transfer has finished, the sequence automatically starts
+	// again with the first descriptor.
+	transfer.setCircularMode(true);
+
+	return transfer;
+}
+
+DmaChannel channel = Dma::channel(0);
+// Transfer object must remain valid while transfer is active
+auto transfer = prepareTransfer();
+
+int main()
+{
+	Board::initialize();
+	initializeDac();
+
+	Dma::initialize();
+
+	channel.startTransfer(transfer);
+
+	while (true)
+	{
+		Led0::toggle();
+		Led1::toggle();
+		modm::delay(500ms);
+
+		MODM_LOG_INFO << "ping" << modm::endl;
+	}
+
+	return 0;
+}

examples/samv71_xplained_ultra/dma/linked_list_transfer/project.xml

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+<library>
+  <extends>modm:samv71-xplained-ultra</extends>
+  <options>
+    <option name="modm:build:build.path">../../../../build/samv71_xplained_ultra/dma_linked_list_transfer</option>
+  </options>
+  <modules>
+    <module>modm:build:scons</module>
+    <module>modm:platform:dac</module>
+    <module>modm:platform:dma</module>
+  </modules>
+</library>