The use of UART in STM32 microcontroller

1. Before using UART, the corresponding peripheral clock must be started, which mainly uses the RCC_APBnPeriphClockCmd function of the firmware library.

Enable UART1: Use RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE)

Enable UART2: use RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2, ENABLE)

2. To use interrupts for UART operations, you need to configure NVIC and set the interrupt priority. For example:

/* Configure the NVIC Preemption Priority Bits */

NVIC_PriorityGroupConfig(NVIC_PriorityGroup_0);

/* Enable the USART1 Interrupt */

NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQChannel;

NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;

NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

NVIC_Init(&NVIC_InitStructure);

3. Configure the corresponding GPIO port.

If the system's UART needs to be remapped, the GPIO_PinRemapConfig function needs to be used for remapping, such as: GPIO_PinRemapConfig(GPIO_Remap_USART2, ENABLE);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING; //Note: Rx is floating, Tx is the second function pull-up.

Configure Rx to floating input mode and Tx to the second power mode with pull-up. And initialize it with GPIO_Init() function. For example:

/* Configure USART2 Rx PA3 input floating */

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3;

GPIO_Init(GPIOA, &GPIO_InitStructure);

/* Configure USART1 Tx (PA.09) as alternate push-pull */

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;

GPIO_InitStructure.GPIO_Speed ​​= GPIO_Speed_50MHz;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;

GPIO_Init(GPIOA, &GPIO_InitStructure);

4. Configure UART

After configuring the correct external crystal oscillator in the conf file, directly write the UART baud rate, communication frame length, mode, hardware communication control, and transceiver mode into the structure defined by USART_InitTypeDef. Then use USART_Init() to initialize. For example:

USART_InitStructure.USART_BaudRate = 9600;

USART_InitStructure.USART_WordLength = USART_WordLength_8b;

USART_InitStructure.USART_StopBits = USART_StopBits_1;

USART_InitStructure.USART_Parity = USART_Parity_No;

USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;

USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;

/* Configure USART1 */

USART_Init(USART1, &USART_InitStructure);[page]

Then enable the transmit and receive interrupts. For example:

/* Enable USART1 Receive and Transmit interrupts */

USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);

USART_ITConfig(USART1, USART_IT_TXE, ENABLE);

// USART_ITConfig(USART1, USART_IT_TXE, DISABLE);

Note: Generally, the TXE interrupt is not enabled. Once this interrupt is enabled, if the UART send buffer is empty, the UART interrupt will be entered immediately. Therefore, the TXE interrupt can be enabled in the program where data needs to be sent. Use USART_SendData() to send data in the UART interrupt.

After enabling the interrupt, you also need to enable the UART port:

like:

/* Enable the USART1 */

USART_Cmd(USART1, ENABLE);

/* Enable the USART2 */

USART_Cmd(USART2, ENABLE);

The interrupt program (stm32f10x_it.c) can complete the sending as follows: Note that all serial port interrupts need to determine the interrupt source in the interrupt service program for separate processing.

void USART1_IRQHandler(void)

{

if(USART_GetITStatus(USART1, USART_IT_RXNE) != RESET)

{

/* Read one byte from the receive data register */

RxBuffer1[RxCounter1++] = USART_ReceiveData(USART1);

if(RxCounter1 == NbrOfDataToRead1)

{

USART_ITConfig(USART1, USART_IT_RXNE, DISABLE); //After sending, disable RXNE.

}

}

if(USART_GetITStatus(USART1, USART_IT_TXE) != RESET)

{

USART_SendData(USART1, TxBuffer1[TxCounter1++]);

if(TxCounter1 == NbrOfDataToTransfer1)

{

USART_ITConfig(USART1, USART_IT_TXE, DISABLE);

}

}

}