[参考译文] TMS570LC4357：按钮去抖

尊敬的 Dobby：

您遇到的不稳定是一个称为“按钮反弹“的常见问题。 按下或松开机械按钮时，触点不会完全闭合或完全断开 — 它们会在 5-20ms 内多次反弹、从而导致 GPIO 寄存器意外变化。

遗憾的是、我没有任何现成的示例、因为大多数这类要求都将由客户自己处理、所以我以前从未遇到过这类问题。

我们有内部 AI、它建议使用如下所示的几个代码流、您可以采用其中的任何一种方法。

方法 1：

// Debounce configuration
#define DEBOUNCE_TIME_MS    20    // Typical debounce time: 10-20ms
#define BUTTON_PRESSED      0     // Assuming active low with pull-up
#define BUTTON_RELEASED     1

// Global variables
static uint32_t lastButtonState = BUTTON_RELEASED;
static uint32_t buttonStateCounter = 0;
static uint32_t stableButtonState = BUTTON_RELEASED;

// Call this function periodically (e.g., every 1ms from a timer interrupt)
uint32_t debounceButton(uint32_t currentButtonState)
{
    if (currentButtonState != lastButtonState) {
        // Button state changed, reset counter
        buttonStateCounter = 0;
        lastButtonState = currentButtonState;
    } else {
        // Button state is stable, increment counter
        if (buttonStateCounter < DEBOUNCE_TIME_MS) {
            buttonStateCounter++;
        }
        
        // If stable for debounce time, update stable state
        if (buttonStateCounter >= DEBOUNCE_TIME_MS) {
            stableButtonState = currentButtonState;
        }
    }
    
    return stableButtonState;
}

// Usage in your main loop or timer ISR
void checkButton(void)
{
    uint32_t rawButtonState = gioGetBit(gioPORTA, BUTTON_PIN); // Read GPIO
    uint32_t debouncedState = debounceButton(rawButtonState);
    
    if (debouncedState == BUTTON_PRESSED) {
        // Button is pressed (stable)
        // Your action here
    }
}

方法 2：

typedef enum {
    BUTTON_STATE_RELEASED,
    BUTTON_STATE_PRESSED,
    BUTTON_STATE_DEBOUNCING_PRESS,
    BUTTON_STATE_DEBOUNCING_RELEASE
} ButtonState_t;

ButtonState_t buttonStateMachine(uint32_t rawInput)
{
    static ButtonState_t state = BUTTON_STATE_RELEASED;
    static uint32_t debounceCounter = 0;
    
    switch(state) {
        case BUTTON_STATE_RELEASED:
            if (rawInput == BUTTON_PRESSED) {
                state = BUTTON_STATE_DEBOUNCING_PRESS;
                debounceCounter = 0;
            }
            break;
            
        case BUTTON_STATE_DEBOUNCING_PRESS:
            if (rawInput == BUTTON_PRESSED) {
                debounceCounter++;
                if (debounceCounter >= DEBOUNCE_TIME_MS) {
                    state = BUTTON_STATE_PRESSED;
                    // Trigger button press event here
                }
            } else {
                state = BUTTON_STATE_RELEASED;
            }
            break;
            
        case BUTTON_STATE_PRESSED:
            if (rawInput == BUTTON_RELEASED) {
                state = BUTTON_STATE_DEBOUNCING_RELEASE;
                debounceCounter = 0;
            }
            break;
            
        case BUTTON_STATE_DEBOUNCING_RELEASE:
            if (rawInput == BUTTON_RELEASED) {
                debounceCounter++;
                if (debounceCounter >= DEBOUNCE_TIME_MS) {
                    state = BUTTON_STATE_RELEASED;
                    // Trigger button release event here
                }
            } else {
                state = BUTTON_STATE_PRESSED;
            }
            break;
    }
    
    return state;
}

硬件配置提示

1. 启用内部上拉/下拉 :使用适合您的按钮电路的内部上拉或下拉电阻器配置 GPIO

2. HALCoGen 配置 :使用 HALCoGen 正确配置 GPIO :

   • 将引脚设置为输入
   • 如果按钮在按下时接地、则启用上拉
   • 如果按下该按钮时连接到 VCC、则启用下拉

用于定期采样的计时器设置

您将需要一个计时器来定期调用去抖功能（建议每 1ms 一次）：

// In HALCoGen, configure RTI (Real-Time Interrupt) for 1ms period
void rtiNotification(uint32 notification)
{
    if(notification == rtiNOTIFICATION_COMPARE0) {
        // Call your button check function here
        checkButton();
    }
}

--

此致、
Jagadish。