DMA with UART for bulk transfer in Embedded C - Mini Project: Build & Apply

DMA with UART for Bulk Transfer

📖 Scenario: You are working on an embedded system that needs to send a large amount of data over UART efficiently. To avoid slowing down the CPU, you will use DMA (Direct Memory Access) to transfer data from a memory buffer to the UART peripheral automatically.

🎯 Goal: Build a simple embedded C program that sets up a data buffer, configures DMA to transfer this buffer over UART, and starts the transfer. This will demonstrate how DMA can handle bulk data transfer without CPU intervention.

📋 What You'll Learn

Create a data buffer array with exact values

Define a DMA transfer size variable

Configure DMA to transfer the buffer to UART data register

Start the DMA transfer and print a confirmation message

💡 Why This Matters

🌍 Real World

DMA with UART is used in embedded devices like sensors, communication modules, and IoT devices to send large data efficiently without blocking the CPU.

💼 Career

Embedded software engineers often configure DMA and UART peripherals to optimize data transfer and improve system performance in real-time applications.

1

Create the data buffer

Create a uint8_t array called data_buffer with these exact 8 values: 0x48, 0x65, 0x6C, 0x6C, 0x6F, 0x21, 0x0A, 0x00.

Embedded C

# Create the data_buffer array with the exact values
# Your code here

Need a hint?

Use uint8_t data_buffer[8] = { ... }; to create the array with the exact bytes.

2

Define DMA transfer size

Create an int variable called transfer_size and set it to the size of data_buffer (which is 8).

Embedded C

#include 

uint8_t data_buffer[8] = {0x48, 0x65, 0x6C, 0x6C, 0x6F, 0x21, 0x0A, 0x00};

// Define transfer_size variable
# Your code here

Need a hint?

Use int transfer_size = 8; to set the transfer size.

3

Configure DMA for UART transfer

Write code to configure DMA to transfer transfer_size bytes from data_buffer to the UART data register at address 0x40013804. Use a pointer volatile uint8_t* called UART_DR for the UART data register. Assume DMA registers are DMA_SRC, DMA_DST, and DMA_CNT. Assign DMA_SRC to data_buffer, DMA_DST to UART_DR, and DMA_CNT to transfer_size. Also, set DMA_START to 1 to start the transfer.

Embedded C

#include 

uint8_t data_buffer[8] = {0x48, 0x65, 0x6C, 0x6C, 0x6F, 0x21, 0x0A, 0x00};

int transfer_size = 8;

// Configure DMA registers for UART transfer
# Your code here

Need a hint?

Use pointers and assign DMA registers as described. Remember to cast the UART address to volatile uint8_t*.

4

Print confirmation of DMA start

Write a printf statement to print exactly: "DMA transfer started for 8 bytes over UART.\n".

Embedded C

#include 
#include 

uint8_t data_buffer[8] = {0x48, 0x65, 0x6C, 0x6C, 0x6F, 0x21, 0x0A, 0x00};

int transfer_size = 8;

volatile uint8_t* UART_DR = (volatile uint8_t*)0x40013804;

volatile uint8_t* DMA_SRC = data_buffer;
volatile uint8_t* DMA_DST = UART_DR;
volatile int DMA_CNT = 0;
volatile int DMA_START = 0;

DMA_SRC = data_buffer;
DMA_DST = UART_DR;
DMA_CNT = transfer_size;
DMA_START = 1;

// Print confirmation message
# Your code here

Need a hint?

Use printf("DMA transfer started for 8 bytes over UART.\n"); inside main().