How to Implement a Circular DMA Buffer for UART on STM32F4 at 9600bps

Implementing a Circular DMA Buffer for UART Communication at 9600bps on an STM32F4 Microcontroller

In this tutorial, we will implement a circular DMA buffer to handle UART communication at 9600bps on an STM32F4 microcontroller. This approach allows for efficient data handling and minimizes CPU load, making it ideal for applications requiring real-time data processing.

Prerequisites

• Basic understanding of microcontrollers and UART communication.
• STM32F4 microcontroller development board.
• STM32CubeIDE or any IDE that supports STM32 development.
• Familiarity with HAL (Hardware Abstraction Layer) library.

Parts/Tools

• STM32F4 microcontroller development board.
• USB to UART converter (if required for serial communication).
• Jumper wires.
• Computer with STM32CubeIDE installed.

Steps

1. Setup the STM32 Project
   • Open STM32CubeIDE and create a new STM32 project.
   • Select your STM32F4 microcontroller model.
   • Enable the UART peripheral in the “Pinout & Configuration” tab.
   • Configure the UART settings:

   
   // Set baud rate to 9600
   huart1.Init.BaudRate = 9600;
               

   • Enable DMA for UART Receive and Transmit.
2. Configure DMA Settings
   • Navigate to the DMA settings in the configuration tab:

   
   DMA_HandleTypeDef hdma_usart1_rx;
               

   • Set the DMA channel and direction:

   
   hdma_usart1_rx.Instance = DMA2_Stream2;
   hdma_usart1_rx.Init.Channel = DMA_CHANNEL_4;
   hdma_usart1_rx.Init.Direction = DMA_PERIPH_TO_MEMORY;
               

   • Set the buffer size and configure the circular mode:

   
   hdma_usart1_rx.Init.Mode = DMA_CIRCULAR;
   hdma_usart1_rx.Init.MemDataAlignment = DMA_MDATAALIGN_BYTE;
   hdma_usart1_rx.Init.PeriphDataAlignment = DMA_PDATAALIGN_BYTE;
   hdma_usart1_rx.Init.BufferSize = BUFFER_SIZE; // Define BUFFER_SIZE as needed
               

3. Implement the Circular Buffer
   • Define a buffer to store incoming data:

   
   #define BUFFER_SIZE 256
   uint8_t rxBuffer[BUFFER_SIZE];
               

   • Initialize the DMA and UART in the main function:

   
   HAL_UART_Receive_DMA(&huart1, rxBuffer, BUFFER_SIZE);
               

4. Handle Received Data
   • Implement a function to process the received data:

   
   void processReceivedData() {
       // Check your buffer and process data
       for (int i = 0; i < BUFFER_SIZE; i++) {
           // Process each byte in the buffer
       }
   }
               

   • Call this function in the main loop or through an interrupt:

   
   while (1) {
       processReceivedData();
   }
               

Troubleshooting

• Issue: No data received
  • Check the UART connection and ensure the correct COM port is selected.
  • Verify the baud rate configuration matches on both microcontroller and terminal.
• Issue: Data corruption
  • Ensure the buffer size is sufficient and correctly defined.
  • Check for overflow by monitoring the buffer index and reset when necessary.
• Issue: DMA transfer not working
  • Ensure DMA is properly configured and enabled in the project settings.
  • Check the interrupt settings for DMA to ensure they are properly set up.

Conclusion

By implementing a circular DMA buffer for UART communication on the STM32F4 microcontroller, we achieve efficient data handling at 9600bps. This setup minimizes CPU usage, allowing the microcontroller to perform other tasks while still receiving data seamlessly. With the steps outlined above, you should be able to integrate this functionality into your projects effectively.