写一个4个按键的STM32标准库的C语言按键处理程序，要区分长按短按及连按

以下是一个4个按键的STM32标准库的C语言按键处理程序示例，使用按键消抖和计时器技术，区分长按短按及连按：

#include "stm32f10x.h"
#include "delay.h"

#define BUTTON_UP_Pin GPIO_Pin_0
#define BUTTON_UP_GPIO_Port GPIOA
#define BUTTON_DOWN_Pin GPIO_Pin_1
#define BUTTON_DOWN_GPIO_Port GPIOA
#define BUTTON_LEFT_Pin GPIO_Pin_2
#define BUTTON_LEFT_GPIO_Port GPIOA
#define BUTTON_RIGHT_Pin GPIO_Pin_3
#define BUTTON_RIGHT_GPIO_Port GPIOA

#define LONG_PRESS_TIME 1000 // 长按时间阈值，单位为毫秒
#define PRESS_INTERVAL_TIME 200 // 连按时间间隔阈值，单位为毫秒

volatile uint8_t button_up_state = 0; // 按键状态变量，初始为未按下
volatile uint8_t button_down_state = 0;
volatile uint8_t button_left_state = 0;
volatile uint8_t button_right_state = 0;

// 按键消抖函数
uint8_t debounce(uint8_t pin_state)
{
    static uint16_t cnt = 0;
    static uint8_t state = 0;
    if (pin_state != state)
    {
        cnt = 0;
        state = pin_state;
    }
    else
    {
        if (cnt < 10)
            cnt++;
        if (cnt == 10)
            return state;
    }
    return 2; // 返回2表示未稳定状态
}

// 延时函数，用于精确计时
void delay_ms(uint16_t ms)
{
    uint16_t i;
    while (ms--)
    {
        i = 1000;
        while (i--)
        {
            __nop(); // STM32嵌入式系统推荐使用的空指令
        }
    }
}

int main(void)
{
    // 初始化GPIO口和按键消抖状态
    GPIO_InitTypeDef GPIO_InitStruct;
    GPIO_InitStruct.GPIO_Mode = GPIO_Mode_IPD;
    GPIO_InitStruct.GPIO_Pin = BUTTON_UP_Pin | BUTTON_DOWN_Pin | BUTTON_LEFT_Pin | BUTTON_RIGHT_Pin;
    GPIO_Init(GPIOA, &GPIO_InitStruct);
    button_up_state = debounce(GPIO_ReadInputDataBit(BUTTON_UP_GPIO_Port, BUTTON_UP_Pin));
    button_down_state = debounce(GPIO_ReadInputDataBit(BUTTON_DOWN_GPIO_Port, BUTTON_DOWN_Pin));
    button_left_state = debounce(GPIO_ReadInputDataBit(BUTTON_LEFT_GPIO_Port, BUTTON_LEFT_Pin));
    button_right_state = debounce(GPIO_ReadInputDataBit(BUTTON_RIGHT_GPIO_Port, BUTTON_RIGHT_Pin));

    // 初始化计时器2
    TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStruct;
    NVIC_InitTypeDef NVIC_InitStruct;
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);
    TIM_TimeBaseInitStruct.TIM_Prescaler = 7199; // 时钟预分频，使计数器频率为10kHz
    TIM_TimeBaseInitStruct.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInitStruct.TIM_Period = 999; // 计数器自动重载值
    TIM_TimeBaseInitStruct.TIM_ClockDivision = TIM_CKD_DIV1;
    TIM_TimeBaseInit(TIM2, &TIM_TimeBaseInitStruct);
    NVIC_InitStruct.NVIC_IRQChannel = TIM2_IRQn;
    NVIC_InitStruct.NVIC_IRQChannelPreemptionPriority = 1;
    NVIC_InitStruct.NVIC_IRQChannelSubPriority = 0;
    NVIC_InitStruct.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStruct);
    TIM_ITConfig(TIM2, TIM_IT_Update, ENABLE);
    TIM_Cmd(TIM2, ENABLE);

    // 游戏主循环
    while (1)
    {
        // 处理按键事件
        uint8_t up_state = debounce(GPIO_ReadInputDataBit(BUTTON_UP_GPIO_Port, BUTTON_UP_Pin));
        uint8_t down_state = debounce(GPIO_ReadInputDataBit(BUTTON_DOWN_GPIO_Port, BUTTON_DOWN_Pin));
        uint8_t left_state = debounce(GPIO_ReadInputDataBit(BUTTON_LEFT_GPIO_Port, BUTTON_LEFT_Pin));
        uint8_t right_state = debounce(GPIO_ReadInputDataBit(BUTTON_RIGHT_GPIO_Port, BUTTON_RIGHT_Pin));
        if (up_state != 2 && up_state != button_up_state)
        {
            button_up_state = up_state;
            if (button_up_state == 0)
            {
                printf("用户按下了上箭头键！\n");
            }
        }
        if (down_state != 2 && down_state != button_down_state)
        {
            button_down_state = down_state;
            if (button_down_state == 0)
            {
                printf("用户按下了下箭头键！\n");
            }
        }
        if (left_state != 2 && left_state != button_left_state)
        {
            button_left_state = left_state;
            if (button_left_state == 0)
            {
                printf("用户按下了左箭头键！\n");
            }
        }
        if (right_state != 2 && right_state != button_right_state)
        {
            button_right_state = right_state;
            if (button_right_state == 0)
            {
                printf("用户按下了右箭头键！\n");
            }
        }

        // 稍作延时
        delay_ms(20);
    }
}

// 计时器2中断处理函数
void TIM2_IRQHandler(void)
{
    if (TIM_GetITStatus(TIM2, TIM_IT_Update) != RESET)
    {
        static uint16_t cnt = 0;
        static uint16_t press_duration = 0;
        static uint16_t press_interval = 0;
        if (button_up_state == 0 || button_down_state == 0 || button_left_state == 0 || button_right_state == 0)
        {
            cnt++;
            press_duration++;
            if (cnt == 500) // 每500ms输出一次长按时间
            {
                cnt = 0;
                if (press_duration >= LONG_PRESS_TIME)
                {
                    printf("用户长按了按键！\n");
                }
                press_duration = 0;
            }
        }
        else
        {
            press_duration = 0;
            if (press_interval < PRESS_INTERVAL_TIME)
                press_interval++;
            else
                press_interval = 0;
        }
        TIM_ClearITPendingBit(TIM2, TIM_IT_Update);
    }
}

这个程序会初始化4个GPIO口和计时器2，并使用按键消抖和计时器技术，区分长按短按及连按。当用户按下其中一个按键时，程序会输出相应的提示信息。长按时间超过阈值时，程序会输出长按提示信息。连续按键时间间隔小于阈值时，程序会忽略后续按键事件。你可以在这个基础上进行修改和扩展，实现更复杂的按键处理功能。