请设计一段代码适用于FS-STM32F407单片机开发平台，构造一个密码验证系统，如果输入的密码错误蜂鸣器响

以下是一个简单的密码验证系统，使用了FS-STM32F407单片机开发平台和一个蜂鸣器模块。代码中默认密码为 "1234"，如果用户输入的密码不正确，蜂鸣器将响一次。

#include "stm32f4xx.h"

#define PASSWORD "1234"

void delay(uint32_t count) {
    for(uint32_t i = 0; i < count; i++) {
        __NOP();
    }
}

int main(void) {
    RCC->AHB1ENR |= RCC_AHB1ENR_GPIODEN;

    GPIOD->MODER |= GPIO_MODER_MODE12_0;
    GPIOD->OTYPER &= ~GPIO_OTYPER_OT12;
    GPIOD->PUPDR &= ~GPIO_PUPDR_PUPD12;

    GPIOD->MODER |= GPIO_MODER_MODE13_0;
    GPIOD->OTYPER &= ~GPIO_OTYPER_OT13;
    GPIOD->PUPDR &= ~GPIO_PUPDR_PUPD13;

    GPIOD->MODER |= GPIO_MODER_MODE14_0;
    GPIOD->OTYPER &= ~GPIO_OTYPER_OT14;
    GPIOD->PUPDR &= ~GPIO_PUPDR_PUPD14;

    GPIOD->MODER |= GPIO_MODER_MODE15_0;
    GPIOD->OTYPER &= ~GPIO_OTYPER_OT15;
    GPIOD->PUPDR &= ~GPIO_PUPDR_PUPD15;

    while(1) {
        // Get user input for password
        char input[5];
        for(int i = 0; i < 4; i++) {
            // Wait for user input
            while(!(USART2->SR & USART_SR_RXNE));
            char c = (char)USART2->DR;
            input[i] = c;
            USART2->DR = c;
            while(!(USART2->SR & USART_SR_TC));
        }
        input[4] = '\0';

        // Check if password is correct
        if(strcmp(input, PASSWORD) == 0) {
            // Password is correct
            GPIOD->ODR |= GPIO_ODR_OD12;
            delay(1000000);
            GPIOD->ODR &= ~GPIO_ODR_OD12;
        } else {
            // Password is incorrect
            GPIOD->ODR |= GPIO_ODR_OD13;
            delay(1000000);
            GPIOD->ODR &= ~GPIO_ODR_OD13;

            // Beep the buzzer once
            GPIOD->ODR |= GPIO_ODR_OD14;
            delay(50000);
            GPIOD->ODR &= ~GPIO_ODR_OD14;
        }
    }
}

代码的主要思路是通过串口从用户那里获取密码输入。首先，我们需要在代码中定义一个默认的密码（在本例中为 "1234"）。然后，我们使用STM32的串口（USART2）获取用户输入的密码。我们等待用户输入四个字符，然后将它们存储在一个字符数组中。接下来，我们将输入的密码与默认密码进行比较。如果密码正确，我们将点亮绿色LED灯1秒钟。如果密码不正确，我们将点亮红色LED灯并发出一声蜂鸣器。