以下是一个使用STM32的标准库（HAL库）实现硬件流控制的串口代码，用于控制UART2：
#include "stm32f4xx_hal.h"
UART_HandleTypeDef huart2;
void SystemClock_Config(void);
int main(void)
{
HAL_Init();
SystemClock_Config();
__HAL_RCC_GPIOA_CLK_ENABLE();
__HAL_RCC_USART2_CLK_ENABLE();
GPIO_InitTypeDef GPIO_InitStruct = {0};
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_FREQ_VERY_HIGH;
GPIO_InitStruct.Alternate = GPIO_AF7_USART2;
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
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_RTS_CTS;
huart2.Init.OverSampling = UART_OVERSAMPLING_16;
if (HAL_UART_Init(&huart2) != HAL_OK)
{
while (1);
}
uint8_t buffer[] = "Hello, world!\r\n";
while (1)
{
if (HAL_UART_Transmit(&huart2, buffer, sizeof(buffer), 100) != HAL_OK)
{
while (1);
}
HAL_Delay(1000);
}
}
void SystemClock_Config(void)
{
RCC_OscInitTypeDef RCC_OscInitStruct = {0};
RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
/** Configure the main internal regulator output voltage
*/
__HAL_RCC_PWR_CLK_ENABLE();
__HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE3);
/** Initializes the CPU, AHB and APB busses clocks
*/
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
RCC_OscInitStruct.HSIState = RCC_HSI_ON;
RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
RCC_OscInitStruct.PLL.PLLM = 16;
RCC_OscInitStruct.PLL.PLLN = 336;
RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV4;
RCC_OscInitStruct.PLL.PLLQ = 7;
if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
{
while (1);
}
/** Initializes the CPU, AHB and APB busses clocks
*/
RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
|RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV4;
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV2;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK)
{
while (1);
}
}
在以上代码中，我们使用了硬件流控制（RTS/CTS）来实现串口的数据传输。在初始化UART时，我们将Mode设置为UART_MODE_TX_RX，以允许UART同时进行发送和接收。我们还将HwFlowCtl设置为UART_HWCONTROL_RTS_CTS，以启用硬件流控制。
此时，CTS引脚应该配置为输入模式，如上述代码所示，我们使用GPIOA2引脚作为CTS。在数据发送时，如果CTS引脚处于逻辑高电平，则UART不会将数据发送到接收端，而会等待CTS引脚返回逻辑低电平，然后再继续发送数据。
请注意，上述代码主要用于示例演示，因此省略了错误处理和异常情况处理。在实际应用中，需要根据具体需求添加适当的错误处理和异常情况处理。
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