请问在KEIL5中使用GETCHAR,将串口输入CH值的值输出，怎么实现

您可以使用以下代码实现在KEIL5中使用GETCHAR，并将串口输入的CH值输出：

#include <stdio.h>
#include <stm32f4xx.h>

int main(void)
{
  // Enable the USART2 peripheral clock
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2, ENABLE);

  // Configure the GPIO pins for USART2
  GPIO_InitTypeDef GPIO_InitStructure;
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2 | GPIO_Pin_3;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
  GPIO_Init(GPIOA, &GPIO_InitStructure);

  // Configure USART2
  USART_InitTypeDef USART_InitStructure;
  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(USART2, &USART_InitStructure);

  // Enable USART2
  USART_Cmd(USART2, ENABLE);

  while(1)
  {
    // Wait for input from the user
    while (USART_GetFlagStatus(USART2, USART_FLAG_RXNE) == RESET);
    // Read the input character
    char ch = USART_ReceiveData(USART2);
    // Print the input character to the USART2
    USART_SendData(USART2, ch);
    // Wait for the transmission to complete
    while (USART_GetFlagStatus(USART2, USART_FLAG_TXE) == RESET);
  }
}

这段代码使用USART2的串口通信接收输入字符，并将输入字符原样输出到串口。请注意，此代码适用于使用STM32F4xx系列控制器的嵌入式系统，如果您使用其他控制器或计算机系统，则应相应地修改代码。