Merge pull request #322 from doragasu/dma_uart_tx

Add UART DMA TX example

examples/uart_tx_dma/Makefile

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+all : flash
+
+TARGET:=uart_tx_dma
+
+include ../../ch32v003fun/ch32v003fun.mk
+
+flash : cv_flash
+clean : cv_clean
+
+

examples/uart_tx_dma/README.md

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+# UART Tx DMA example
+
+This example shows how to use DMA to send data through the UART peripheral. The sample code does the following:
+
+* Send the "Hello World!\r\n" string each second through the UART peripheral, using DMA.
+* Toggling a LED each time the DMA transfer is completed, by using the transmission complete interrupt.
+
+The code is extensively commented, so it should be easy to follow and modify.
+
+# Usage
+
+## Wiring
+
+This code can be run as-is in the [nanoch32V003 board](https://github.com/wuxx/nanoCH32V003). The GPIO pin used for the UART Tx funcion is `D5`. It must be connected to a UART receiver (such as a CP2102 board or similar) configured for 115200 bps, no parity and one stop bit.
+
+The example also uses the nanoch32V003 on-board LED connected to `D6`. On any other board either connect a LED to `D6` or edit the code to remap the pin to match your hardware setup.
+
+## Running
+
+Build and flash the project. You should see the LED toggling each second and the UART receiver should get the "Hello World!" message once per second.

examples/uart_tx_dma/funconfig.h

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+#ifndef _FUNCONFIG_H
+#define _FUNCONFIG_H
+
+#define CH32V003           1
+
+#endif
+

examples/uart_tx_dma/uart_tx_dma.c

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+/*
+ * This example uses DMA for the UART to transfer the "Hello World!\r\n" string
+ * once per second. Connect a UART Rx pin to D5, flash the example, setup your
+ * uart for 115200n1 and the messages should appear
+ */
+
+#include "ch32v003fun.h"
+
+// Set UART baud rate here
+#define UART_BR 115200
+// LED on D6 (nanoCH32V003 board)
+#define LED_PIN 6
+
+// DMA transfer completion interrupt. It will fire when the DMA transfer is
+// complete. We use it just to blink the LED
+__attribute__((interrupt)) __attribute__((section(".srodata")))
+void DMA1_Channel4_IRQHandler(void)
+{
+	// Clear flag
+	DMA1->INTFCR |= DMA_CTCIF4;
+
+	// Blink LED
+	GPIOD->OUTDR ^= 1<<LED_PIN;
+}
+
+static void led_setup(void)
+{
+	RCC->APB2PCENR = RCC_APB2Periph_GPIOD;
+	GPIOD->CFGLR =
+		((GPIO_CNF_IN_PUPD)<<(4*1)) | // Keep SWIO enabled.
+		(GPIO_Speed_2MHz | GPIO_CNF_OUT_PP)<<(4*LED_PIN);
+
+	// LED ON
+	GPIOD->BSHR = 1<<LED_PIN;
+}
+
+static void uart_setup(void)
+{
+	// Enable UART and GPIOD
+	RCC->APB2PCENR |= RCC_APB2Periph_GPIOD | RCC_APB2Periph_USART1;
+
+	// Push-Pull, 10MHz Output on D5, with AutoFunction
+	GPIOD->CFGLR = (GPIOD->CFGLR & ~(0xF<<(4*5))) |
+			((GPIO_Speed_10MHz | GPIO_CNF_OUT_PP_AF)<<(4*5));
+
+	// Setup UART for Tx 8n1
+	USART1->CTLR1 = USART_WordLength_8b | USART_Parity_No | USART_Mode_Tx;
+	USART1->CTLR2 = USART_StopBits_1;
+	// Enable Tx DMA event
+	USART1->CTLR3 = USART_DMAReq_Tx;
+
+	// Set baud rate and enable UART
+	USART1->BRR = ((FUNCONF_SYSTEM_CORE_CLOCK) + (UART_BR)/2) / (UART_BR);
+	USART1->CTLR1 |= CTLR1_UE_Set;
+}
+
+static void dma_uart_setup(void)
+{
+	// Enable DMA peripheral
+	RCC->AHBPCENR = RCC_AHBPeriph_SRAM | RCC_AHBPeriph_DMA1;
+
+	// Disable channel just in case there is a transfer in progress
+	DMA1_Channel4->CFGR &= ~DMA_CFGR1_EN;
+
+	// USART1 TX uses DMA channel 4
+	DMA1_Channel4->PADDR = (uint32_t)&USART1->DATAR;
+	// MEM2MEM: 0 (memory to peripheral)
+	// PL: 0 (low priority since UART is a relatively slow peripheral)
+	// MSIZE/PSIZE: 0 (8-bit)
+	// MINC: 1 (increase memory address)
+	// CIRC: 0 (one shot)
+	// DIR: 1 (read from memory)
+	// TEIE: 0 (no tx error interrupt)
+	// HTIE: 0 (no half tx interrupt)
+	// TCIE: 1 (transmission complete interrupt enable)
+	// EN: 0 (do not enable DMA yet)
+	DMA1_Channel4->CFGR = DMA_CFGR1_MINC | DMA_CFGR1_DIR | DMA_CFGR1_TCIE;
+
+	// Enable channel 4 interrupts
+	NVIC_EnableIRQ(DMA1_Channel4_IRQn);
+}
+
+static void dma_uart_tx(const void *data, uint32_t len)
+{
+	// Disable DMA channel (just in case a transfer is pending)
+	DMA1_Channel4->CFGR &= ~DMA_CFGR1_EN;
+	// Set transfer length and source address
+	DMA1_Channel4->CNTR = len;
+	DMA1_Channel4->MADDR = (uint32_t)data;
+	// Enable DMA channel to start the transfer
+	DMA1_Channel4->CFGR |= DMA_CFGR1_EN;
+}
+
+int main(void)
+{
+	static const char message[] = "Hello World!\r\n";
+
+	SystemInit();
+	led_setup();
+	uart_setup();
+	dma_uart_setup();
+
+	while (1)
+	{
+		dma_uart_tx(message, sizeof(message) - 1);
+		Delay_Ms(1000);
+	}
+}