📸 v1 with circular operation

Author: csrohit

dma/.vscode/settings.json

@@ -0,0 +1,6 @@
+{
+    "files.associations": {
+        "time.h": "c",
+        "timer.h": "c"
+    }
+}

dma/Makefile

@@ -15,7 +15,7 @@ CXXSTD		:= c++17
 
 # Project specific configuration
 BUILD_DIR 	:= build
-BUILD_TYPE	?= Release
+BUILD_TYPE	?= Debug
 SRC_DIR 	:= src
 INC_DIRS	= include
 

dma/docs/blue-pill-pinout.png

@@ -0,0 +1,24 @@
+#include <stm32f1xx.h>
+
+#ifndef __DMA_H__
+#define __DMA_H__
+typedef enum
+{
+    DISABLE,
+    ENABLE
+} dma_channel_cmd_t;
+
+inline void dma_channel_cmd(DMA_Channel_TypeDef *ch, dma_channel_cmd_t cmd)
+{
+    if(cmd == ENABLE){
+        ch->CCR |= DMA_CCR_EN;
+    }else{
+        ch->CCR &= ~DMA_CCR_EN;
+    }
+}
+
+inline void dma_channel_reload(DMA_Channel_TypeDef *ch, uint32_t new_count){
+    ch->CNDTR = new_count;
+}
+
+#endif

dma/docs/elf_str.drawio

@@ -1,6 +1,8 @@
 #ifndef __MAIN_H__
 
 #define __MAIN_H__
+int main(void);
+
 /**
  * @brief enable clock for dma1 peripheral registers
  */
@@ -12,8 +14,8 @@ void dma1_clock_enable(void);
 void dma_usart_tx_init(void);
 
 /**
- * @brief Configure DMA1 channel 4 to work with USART1 transmitter
- * It reads from memory and writes to USART data register
+ * @brief Configure DMA1 channel 5 to work with USART1 receiver
+ * It reads from USART data register and writes to memory
  */
 void dma_usart_rx_init(void);
 
@@ -23,7 +25,7 @@ void dma_usart_rx_init(void);
 void dma_usart_tx_enable(void);
 
 /**
- * @brief Enable DMA to accept request for channel 4
+ * @brief Enable DMA to accept request for channel 5
  */
 void dma_usart_rx_enable(void);
 

dma/docs/linker-script.drawio

@@ -1,6 +1,9 @@
-#pragma once
+
 #include<stdint.h>
 
+#ifndef __TIMER_H__
+#define __TIMER_H__
+
 /**
  * @brief Stores number of systick interrupts
  * 
@@ -15,7 +18,9 @@ extern volatile uint32_t msTicks;
 void delay(uint32_t ms);
 
 /**
- * @brief Event handler for systick timer overflow event
- * As address of this function is to be inserted in the vector table, this should not be made inline
+ * @brief Interrupt handler for systick timer
+ * should not be made inline as address of this handler is to be placed in the vector table
  */
-void SysTick_Handler(void);
+void SysTick_Handler(void);
+
+#endif

dma/docs/out_115200_circ.png

@@ -15,16 +15,10 @@
 #include <stdint.h>
 #include <stdio.h>
 #include <stm32f1xx.h>
-
-#include <time.h>
+#include <timer.h>
 #include <main.h>
 
-#define RX_BUFFER_LENGTH 20U
-#define TX_BUFFER_LENGTH 13U
-
-const char *msg = "Hello world\r\n\0";
-
-char buff[RX_BUFFER_LENGTH];
+const char * msg = "Hello world\r\n\0";
 
 void dma1_clock_enable(void)
 {
@@ -41,7 +35,7 @@ void dma_usart_tx_init(void)
 	DMA1_Channel4->CMAR = (uint32_t)msg;
 
 	// set number od dma transactions
-	DMA1_Channel4->CNDTR = RX_BUFFER_LENGTH;
+	DMA1_Channel4->CNDTR = 13;
 
 	// set memory address incement by 1byte
 	DMA1_Channel4->CCR |= DMA_CCR_MINC;
@@ -73,7 +67,7 @@ void usart1_init(void)
 	GPIOA->CRH |= GPIO_CRH_CNF10_0;
 
 	// set baud rate as 9600
-	uint32_t baud = (uint32_t)(SystemCoreClock / 9600);
+	uint32_t baud = (uint32_t)(SystemCoreClock / 115200);
 	USART1->BRR = baud;
 
 	// Enable transmitter
@@ -91,13 +85,8 @@ void usart1_enable(void)
 int main(void)
 {
 	dma1_clock_enable();
-	SysTick_Config(SystemCoreClock / 1000);
 	usart1_init();
 	dma_usart_tx_init();
 	dma_usart_tx_enable();
 	usart1_enable();
-
-	while (1)
-	{
-	}
 }