帮我写stm32f407用4x4矩阵按键代码

好的，以下是一个简单的4x4矩阵按键的代码示例，使用了GPIO外设和中断：

#include "stm32f4xx.h"

#define ROW1 GPIO_Pin_0
#define ROW2 GPIO_Pin_1
#define ROW3 GPIO_Pin_2
#define ROW4 GPIO_Pin_3
#define COL1 GPIO_Pin_4
#define COL2 GPIO_Pin_5
#define COL3 GPIO_Pin_6
#define COL4 GPIO_Pin_7

void init_GPIO(void);
void init_NVIC(void);
void EXTI0_IRQHandler(void);
void EXTI1_IRQHandler(void);
void EXTI2_IRQHandler(void);
void EXTI3_IRQHandler(void);

volatile uint8_t key_pressed = 0;

int main(void)
{
    init_GPIO();
    init_NVIC();

    while (1)
    {
        if (key_pressed)
        {
            // Do something when a key is pressed
            key_pressed = 0; // Clear the flag
        }
    }
}

void init_GPIO(void)
{
    GPIO_InitTypeDef GPIO_InitStruct;

    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);

    // Configure rows as inputs with pull-up resistors
    GPIO_InitStruct.GPIO_Pin = ROW1 | ROW2 | ROW3 | ROW4;
    GPIO_InitStruct.GPIO_Mode = GPIO_Mode_IN;
    GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_UP;
    GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOA, &GPIO_InitStruct);

    // Configure columns as outputs
    GPIO_InitStruct.GPIO_Pin = COL1 | COL2 | COL3 | COL4;
    GPIO_InitStruct.GPIO_Mode = GPIO_Mode_OUT;
    GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOA, &GPIO_InitStruct);

    // Set columns high
    GPIO_SetBits(GPIOA, COL1 | COL2 | COL3 | COL4);
}

void init_NVIC(void)
{
    NVIC_InitTypeDef NVIC_InitStruct;

    // Enable EXTI interrupts
    NVIC_InitStruct.NVIC_IRQChannel = EXTI0_IRQn;
    NVIC_InitStruct.NVIC_IRQChannelPreemptionPriority = 0;
    NVIC_InitStruct.NVIC_IRQChannelSubPriority = 0;
    NVIC_InitStruct.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStruct);

    NVIC_InitStruct.NVIC_IRQChannel = EXTI1_IRQn;
    NVIC_InitStruct.NVIC_IRQChannelPreemptionPriority = 0;
    NVIC_InitStruct.NVIC_IRQChannelSubPriority = 0;
    NVIC_InitStruct.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStruct);

    NVIC_InitStruct.NVIC_IRQChannel = EXTI2_IRQn;
    NVIC_InitStruct.NVIC_IRQChannelPreemptionPriority = 0;
    NVIC_InitStruct.NVIC_IRQChannelSubPriority = 0;
    NVIC_InitStruct.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStruct);

    NVIC_InitStruct.NVIC_IRQChannel = EXTI3_IRQn;
    NVIC_InitStruct.NVIC_IRQChannelPreemptionPriority = 0;
    NVIC_InitStruct.NVIC_IRQChannelSubPriority = 0;
    NVIC_InitStruct.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStruct);

    // Configure EXTI interrupts for rows
    EXTI_InitTypeDef EXTI_InitStruct;
    EXTI_InitStruct.EXTI_Line = EXTI_Line0 | EXTI_Line1 | EXTI_Line2 | EXTI_Line3;
    EXTI_InitStruct.EXTI_Mode = EXTI_Mode_Interrupt;
    EXTI_InitStruct.EXTI_Trigger = EXTI_Trigger_Falling;
    EXTI_InitStruct.EXTI_LineCmd = ENABLE;
    EXTI_Init(&EXTI_InitStruct);
}

void EXTI0_IRQHandler(void)
{
    if (EXTI_GetITStatus(EXTI_Line0) != RESET)
    {
        key_pressed = 1;
        EXTI_ClearITPendingBit(EXTI_Line0);
    }
}

void EXTI1_IRQHandler(void)
{
    if (EXTI_GetITStatus(EXTI_Line1) != RESET)
    {
        key_pressed = 2;
        EXTI_ClearITPendingBit(EXTI_Line1);
    }
}

void EXTI2_IRQHandler(void)
{
    if (EXTI_GetITStatus(EXTI_Line2) != RESET)
    {
        key_pressed = 3;
        EXTI_ClearITPendingBit(EXTI_Line2);
    }
}

void EXTI3_IRQHandler(void)
{
    if (EXTI_GetITStatus(EXTI_Line3) != RESET)
    {
        key_pressed = 4;
        EXTI_ClearITPendingBit(EXTI_Line3);
    }
}

注意，这个示例代码针对的是4x4矩阵按键，如果你的矩阵按键不是4x4的，需要相应地修改引脚定义和中断处理函数。另外，这个示例代码只是一个简单的例子，实际使用时还需要考虑去抖动和多键同时按下等情况。