You are required to write a C program to: • Initialize GPIO peripherals • Initialise UART peripheral for receiving ASCII characters ‘A’ to ‘Z’ at baud 9600 • Initialise an internal array to hold 10 characters with head and tail: CharBuff • Repeat the following:o When data is received on the serial communication port, read ASCII character X, o If received character X is a capital letter add it to CharBuff, else ignore. o While CharBuff is not empty, transmit the morse code of the oldest stored character by blinking the LED (code provided for you). o When CharBuff is full, disable UART RX. o If UART RX is disabled, pushing the button P_B1 will activate it; otherwise, pushing the button does not affect your programme. You are recommended to use interrupt to control UART receiving data and coordinate the operation between CharBuff and P_LD2. 其中，启用uart代码位uart_enable();

以下是一个简单的示例程序，演示了如何实现上述要求：

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

#define BUF_SIZE 10

// 初始化 GPIO
void init_gpio() {
    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
    
    GPIO_InitTypeDef GPIO_InitStructure;
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5; // LD2
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
    GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOA, &GPIO_InitStructure);
    
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0; // P_B1
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN;
    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
    GPIO_Init(GPIOA, &GPIO_InitStructure);
}

// 初始化 UART
void init_uart() {
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2, ENABLE);
    
    USART_InitTypeDef USART_InitStructure;
    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_Init(USART2, &USART_InitStructure);
    
    NVIC_InitTypeDef NVIC_InitStructure;
    NVIC_InitStructure.NVIC_IRQChannel = USART2_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);
    
    USART_ITConfig(USART2, USART_IT_RXNE, ENABLE);
    
    USART_Cmd(USART2, ENABLE);
}

// 定义 morse 码表
const char* morse_table[] = {
    ".-", "-...", "-.-.", "-..", ".", "..-.", "--.", "....", "..", ".---", "-.-",
    ".-..", "--", "-.", "---", ".--.", "--.-", ".-.", "...", "-", "..-", "...-",
    ".--", "-..-", "-.--", "--.."
};

// 定义字符缓冲区
char char_buff[BUF_SIZE];
int head = 0;
int tail = 0;
int count = 0;
int uart_enabled = 1;

// 将一个大写字母转换为 morse 码
void blink_morse(char c) {
    if (c >= 'A' && c <= 'Z') {
        const char* morse = morse_table[c - 'A'];
        for (int i = 0; morse[i] != '\0'; i++) {
            if (morse[i] == '.') {
                GPIO_SetBits(GPIOA, GPIO_Pin_5); // LD2 on
                delay(100);
                GPIO_ResetBits(GPIOA, GPIO_Pin_5); // LD2 off
                delay(100);
            } else if (morse[i] == '-') {
                GPIO_SetBits(GPIOA, GPIO_Pin_5); // LD2 on
                delay(300);
                GPIO_ResetBits(GPIOA, GPIO_Pin_5); // LD2 off
                delay(100);
            }
        }
        delay(200);
    }
}

// 中断处理函数，当有数据接收时调用
void USART2_IRQHandler(void) {
    if (USART_GetITStatus(USART2, USART_IT_RXNE) != RESET) {
        char c = USART_ReceiveData(USART2);
        if (c >= 'A' && c <= 'Z') {
            if (count < BUF_SIZE) {
                char_buff[tail] = c;
                tail = (tail + 1) % BUF_SIZE;
                count++;
                if (count == BUF_SIZE) {
                    uart_enabled = 0;
                    USART_ITConfig(USART2, USART_IT_RXNE, DISABLE);
                }
            }
        }
    }
}

int main(void) {
    init_gpio();
    init_uart();
    
    while (1) {
        if (!uart_enabled && GPIO_ReadInputDataBit(GPIOA, GPIO_Pin_0) == RESET) {
            // 如果 UART RX 被禁用并且 P_B1 被按下，则重新启用 UART RX
            head = 0;
            tail = 0;
            count = 0;
            uart_enabled = 1;
            USART_ITConfig(USART2, USART_IT_RXNE, ENABLE);
        }
        if (count > 0) {
            blink_morse(char_buff[head]);
            head = (head + 1) % BUF_SIZE;
            count--;
        }
    }
    
    return 0;
}

这段代码使用 STM32F4 系列芯片作为开发板，通过 GPIO 控制板载 LED（LD2）的闪烁来输出 Morse 电码，通过 UART 串口接收来自外部设备的 ASCII 字符，将收到的大写字母存储在内部缓冲区（CharBuff）中，并在收到每个字符后立即将其转换为 Morse 电码输出。如果缓冲区已满，则禁用 UART 接收，并在按下按钮后重新启用它。