二、串口的使用步骤
（1）中断方式
基本步骤是初试化时钟，脚位、波特率设置、安装中断服务程序、开中断等，参考代码如下：
void uart_init(void)
{
USART_InitTypeDef USART_InitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
GPIO_InitTypeDef GPIO_InitStructure;
/* Enable GPIO clock */
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC, ENABLE);
/* Enable USART clock */
RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART3, ENABLE);
/* Connect USART pins to AF7 */
GPIO_PinAFConfig(GPIOC, GPIO_PinSource10, GPIO_AF_USART3);
GPIO_PinAFConfig(GPIOC, GPIO_PinSource11, GPIO_AF_USART3);
/* Configure USART Tx and Rx as alternate function push-pull */
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;
GPIO_Init(GPIOC, &GPIO_InitStructure);
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_11;
GPIO_Init(GPIOC, &GPIO_InitStructure);
/* USARTx configuration ----------------------------------------------------*/
/* USARTx configured as follow:
- BaudRate = 3750000 baud
- Maximum BaudRate that can be achieved when using the Oversampling by 8
is: (USART APB Clock / 8)
Example:
- (USART3 APB1 Clock / 8) = (30 MHz / 8) = 3750000 baud
- (USART1 APB2 Clock / 8) = (60 MHz / 8) = 7500000 baud
- Maximum BaudRate that can be achieved when using the Oversampling by 16
is: (USART APB Clock / 16)
Example: (USART3 APB1 Clock / 16) = (30 MHz / 16) = 1875000 baud
Example: (USART1 APB2 Clock / 16) = (60 MHz / 16) = 3750000 baud
- Word Length = 8 Bits
- one Stop Bit
- No parity
- Hardware flow control disabled (RTS and CTS signals)
- Receive and transmit enabled
*/
USART_InitStructure.USART_BaudRate = 115200;
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;
USART_Init(USART3, &USART_InitStructure);
/* NVIC configuration */
/* Configure the Priority Group to 2 bits */
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);
/* Enable the USARTx Interrupt */
NVIC_InitStructure.NVIC_IRQChannel = USART3_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
/* Enable USART */
USART_Cmd(USART3, ENABLE);
USART_ITConfig(USART3, USART_IT_RXNE, ENABLE);
}
中断服务程序如下：
void USART3_IRQHandler(void)
{
unsigned char ch;
if(USART_GetITStatus(USART3, USART_IT_RXNE) != RESET)
{
/* Read one byte from the receive data register */
ch = (USART_ReceiveData(USART3));
printf("in[%c].\r\n",ch);
}
}
直接把接收到的字符打印出来。
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