Nucleo STM32f103RB/F4 Discovery

Question

Has anybody used Duplex communication via VCP on Nucleo/or discovery single USART with RX TX interrupts.

Would appreciate sample code to Echo back(transmit) what is received .

Answer 1

There are certainly some example among the STM32CubeF4 and STM32CubeF1 package.

Also see this example, in which the microcontroller echos back the received bytes to the sender using UART RX interrupt:

#include "stm32f4xx.h"

UART_HandleTypeDef huart2;

/* Single byte to store input */
uint8_t byte;

void SystemClock_Config(void);

/* UART2 Interrupt Service Routine */
void USART2_IRQHandler(void)
{
  HAL_UART_IRQHandler(&huart2);
}

/* This callback is called by the HAL_UART_IRQHandler when the given number of bytes are received */
void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{
  if (huart->Instance == USART2)
  {
    /* Transmit one byte with 100 ms timeout */
    HAL_UART_Transmit(&huart2, &byte, 1, 100);

    /* Receive one byte in interrupt mode */ 
    HAL_UART_Receive_IT(&huart2, &byte, 1);
  }
}

void uart_gpio_init()
{
  GPIO_InitTypeDef GPIO_InitStruct;

  __GPIOA_CLK_ENABLE();

  /**USART2 GPIO Configuration
  PA2     ------> USART2_TX
  PA3     ------> USART2_RX
  */
  GPIO_InitStruct.Pin = GPIO_PIN_2 | GPIO_PIN_3;
  GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
  GPIO_InitStruct.Pull = GPIO_PULLUP;
  GPIO_InitStruct.Speed = GPIO_SPEED_LOW;
  GPIO_InitStruct.Alternate = GPIO_AF7_USART2;
  HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
}

void uart_init()
{
  __USART2_CLK_ENABLE();

  huart2.Instance = USART2;
  huart2.Init.BaudRate = 115200;
  huart2.Init.WordLength = UART_WORDLENGTH_8B;
  huart2.Init.StopBits = UART_STOPBITS_1;
  huart2.Init.Parity = UART_PARITY_NONE;
  huart2.Init.Mode = UART_MODE_TX_RX;
  huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart2.Init.OverSampling = UART_OVERSAMPLING_16;
  HAL_UART_Init(&huart2);

  /* Peripheral interrupt init*/
  HAL_NVIC_SetPriority(USART2_IRQn, 0, 0);
  HAL_NVIC_EnableIRQ(USART2_IRQn);
}

int main(void)
{
  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();

  uart_gpio_init();
  uart_init();

  HAL_UART_Receive_IT(&huart2, &byte, 1);

  while(1)
  {

  }
}

1. Initialize the GPIO pins of the UART.

   a. Enable the appropriate GPIO port's clock.

   b. Configure the UART pins in alternate function mode.

2. Initialize the UART peripheral.

   a. Enable the clock of the appropriate UART peripheral.

   b. Configure BAUD rate, word length, stop and parity bits, flow control etc.

   c. Enable the UART IRQ in NVIC and set the priority.

3. Call the HAL_UART_IRQHandler(UART_HandleTypeDef* huart); in the UART ISR (USART2_IRQHandler).

4. The HAL_UART_IRQHandler will call the HAL_UART_RxCpltCallback when the receive procedure is complete. In this callback you can transmit the received bytes.

5. Start the echo loop with a single HAL_UART_Receive_IT(&huart2, &byte, 1); call.