✨working with circular mode

Author: csrohit

dma/include/main.h

@@ -0,0 +1,12 @@
+#ifndef __MAIN_H__
+
+#define __MAIN_H__
+
+void dma_usart_tx_init(void);
+void dma_usart_rx_init(void);
+void dma_usart_tx_enable(void);
+void dma_usart_rx_enable(void);
+void usart1_init(void);
+void usart1_enable(void);
+
+#endif

dma/include/uart.h

@@ -8,8 +8,7 @@
  *
  * This software component is licensed by Rohit Nimkar under BSD 3-Clause license,
  * the "License"; You may not use this file except in compliance with the
- * License. You may obtain a copy of the License at:
- *                        opensource.org/licenses/BSD-3-Clause
+ * License. You may obtain a copy of the License at: opensource.org/licenses/BSD-3-Clause
  *
  ******************************************************************************
  */
@@ -18,20 +17,53 @@
 #include <stm32f1xx.h>
 
 #include <time.h>
-#include <uart.h>
+#include <main.h>
 
-char msg[28] = "Hello world\r\n\0";
+#define RX_BUFFER_LENGTH 20U
+#define TX_BUFFER_LENGTH 13U
 
-int main(void)
-{
+const char* msg = "Hello world\r\n\0";
+
+char buff[RX_BUFFER_LENGTH];
+
+
+/**
+ * @brief Configure DMA1 channel 4 to work with USART1 transmitter
+ * It reads from memory and writes to USART data register
+ */
+void dma_usart_tx_init(void){
+	// enable clock for dma peripheral registers
 	RCC->AHBENR |= RCC_AHBENR_DMA1EN;
 
+	// USART TX is mapped to DMA1 channel 4
+	// set peripheral address to USART data register
 	DMA1_Channel4->CPAR = (uint32_t) &USART1->DR;
+
+	// set memory address to address of string
 	DMA1_Channel4->CMAR = (uint32_t) msg;
-	DMA1_Channel4->CNDTR = 13U;
-	DMA1_Channel4->CCR |= DMA_CCR_MINC | DMA_CCR_CIRC | DMA_CCR_DIR;
 
-	  // enable clock for GPIOA and USART1
+	// set number od dma transactions
+	DMA1_Channel4->CNDTR = RX_BUFFER_LENGTH;
+
+	// set memory address incement by 1byte
+	DMA1_Channel4->CCR |= DMA_CCR_MINC;
+
+	// enable circular mode
+	DMA1_Channel4->CCR |= DMA_CCR_CIRC;
+
+	// set data transfer direction - memory -> peripheral
+	DMA1_Channel4->CCR |= DMA_CCR_DIR;
+}
+
+/**
+ * @brief Enable DMA to accept request for channel 4
+ */
+void dma_usart_tx_enable(void){
+	DMA1_Channel4->CCR |= DMA_CCR_EN;
+}
+
+void usart1_init(void){
+	// enable clock for GPIOA and USART1
     RCC->APB2ENR |= RCC_APB2ENR_USART1EN | RCC_APB2ENR_IOPAEN;
 
     // reset pin configurations for PA9 and PA10
@@ -43,34 +75,35 @@ int main(void)
     // PA10 as floating input
     GPIOA->CRH |= GPIO_CRH_CNF10_0;
 
+	// set baud rate as 9600
     uint32_t baud = (uint32_t)(SystemCoreClock / 9600);
-
     USART1->BRR = baud;
 
-    USART1->CR3 |= USART_CR3_DMAT;
-
-	DMA1_Channel4->CCR |= DMA_CCR_EN;
-    // transmitter enable, receiver enable, receiver interrupt enable and USART enable
-    USART1->CR1 = USART_CR1_TE | USART_CR1_RE | USART_CR1_RXNEIE | USART_CR1_UE;
-
-
-
-    // enable USART1 interrupt
-    // NVIC_EnableIRQ(USART1_IRQn);
+	// Enable transmitter
+	USART1->CR1 |= USART_CR1_TE;
 
+	// Enable DMA mode for transmitter
+    USART1->CR3 |= USART_CR3_DMAT;
+}
 
+/**
+ * @brief Enable USART1 prescalers and output
+ */
+void usart1_enable(void){
+	USART1->CR1 |= USART_CR1_UE;
+}
 
-	// USART1_init(9600U);
-	
-	int ret = SysTick_Config(SystemCoreClock/1000);
-	if (ret < 0)
-		while (1)
-			;
+int main(void)
+{
+	SysTick_Config(SystemCoreClock/1000);
+	usart1_init();
+	dma_usart_tx_init();
+	dma_usart_tx_enable();
+	usart1_enable();
 
 	while (1)
 	{	
-		// USART1_puts(msg);
-		// delay(5000U);
+		
 	}
 
 

dma/src/main.c

@@ -2,6 +2,7 @@
 // See: RM0008 10.1.2 Interrupt and exception vectors, Table 63. Vector table for other STM32F10xxx devices
 
 #include <stdint.h>
+#include <stm32f1xx.h>
 
 extern uint32_t _etext;
 extern uint32_t _sdata;

dma/src/startup_stm32f1.c

@@ -1,4 +1,4 @@
-#include<timer.h>
+#include<time.h>
 
 volatile uint32_t msTicks = 0;