The Ultimate Key Scanner Discussion

1. Idea

Based on STM8, the idea of ​​key processing is as follows:

Scan the keys every 20ms or so, use key_now to record the current value, and use key_last to record the last value. If key_now and key_last are valid at the same time, start cnt++.

I set two thresholds, LONG_PRESS is 100 (100*20ms=2s) and SHORT_PRESS is 4 (4*20ms=80ms, debounce).

If cnt is greater than LONG_PRESS, it means it is a long press. Otherwise, check whether cnt is greater than SHORT_PRESS, which means it is a short press. Otherwise, clear cnt.

In another case, when we are setting parameters, we need to keep adding or subtracting 1. I press and hold, hoping that the value will increase or decrease continuously. How can I achieve this?

Connect to the above cnt value and set a continuous press threshold, MID_PRESS=50 (50*20ms=1s).

When cnt is greater than MID_PRESS, I think the short press is triggered, but at this time cnt is not cleared, but cnt is subtracted from the value of SHORT_PRESS.

In this way, if the button is not released, the short press will be triggered continuously.

2. Implementation

There are three buttons on the hardware: set, up, and down.

//Control key duration 

#define LONG_PRESS 100 // 20ms*100=2s, long press 

#define SHORT_PRESS 5 // 20ms*5=100ms, short press 

#define MID_PRESS 50 // 20ms*50=1s，连按 

#define REPEAT_PRESS 5 // 200ms*5=100ms, press sensitivity parameter 

#define KEY_PORT (GPIOC) 

#define KEY_SET (GPIO_PIN_5) // set键接PC5 

#define KEY_UP (GPIO_PIN_6) // up键接PC6 

#define KEY_DOWN (GPIO_PIN_7) // down键接PC7

float pinNow; 

bool pinSet_now, pinUp_now, pinDown_now; 

bool pinSet_last, pinUp_last, pinDown_last; 

bool set_long = FALSE; // set键长按 

bool set_short = FALSE; // set key short press 

bool up_short = FALSE; // up key short press 

bool down_short = FALSE; // down key short press

// Initialization 

void key_proc_init(void) 

{ 

    GPIO_Init(KEY_PORT, KEY_SET|KEY_UP|KEY_DOWN, GPIO_MODE_IN_FL_IT); 

    EXTI_SetExtIntSensitivity(EXTI_PORT_GPIOC, EXTI_SENSITIVITY_FALL_ONLY);

    pinNow = 0; 

    set_cnt = 0; 

    up_cnt = 0; 

    down_cnt = 0;

    set_long = FALSE; 

    set_short = FALSE; 

    up_short = FALSE; 

    down_short = FALSE; 

}

//Key processing 

void key_scan(void) 

{ 

    //The button port is pulled up, the default is high level, and it becomes low when a button is pressed. Here it is inverted, and it becomes high when a button is pressed. 

    pinNow = 0xFF - GPIO_ReadInputData(KEY_PORT); 

    pinSet_now = pinNow & KEY_SET; 

    pinUp_now = pinNow & KEY_UP; 

    pinDown_now = pinNow & KEY_DOWN;

    // The set key can only be pressed long or short, not continuously. 

    if (pinSet_now & pinSet_last) { 

        set_cnt++; 

        if (set_cnt>LONG_PRESS) { 

            set_long = TRUE; 

            set_cnt = 0; 

        } 

    }else { 

        if (set_cnt>SHORT_PRESS) { 

            set_short = TRUE; 

            set_cnt = 0; 

        }else{ 

            set_cnt = 0; 

        } 

    } 

    // The up and down keys have continuous press and short press, but no long press 

    if (pinUp_now & pinUp_last) { 

        up_cnt++; 

        if (up_cnt>MID_PRESS) { 

            up_short = TRUE; 

            up_cnt = up_cnt - REPEAT_PRESS; 

        } 

    }else{ 

        if (up_cnt>SHORT_PRESS) { 

            up_short = TRUE; 

            up_cnt = 0; 

        } 

    }

    if (pinDown_now & pinDown_last) { 

        down_cnt++; 

        if (down_cnt>MID_PRESS) { 

            down_short = TRUE; 

            down_cnt = down_cnt - REPEAT_PRESS; 

        } 

    }else{ 

        if (down_cnt>SHORT_PRESS) { 

            down_short = TRUE; 

            down_cnt = 0; 

        } 

    }

    // Add your own processing code for set_long, set_short, up_short, down_short 

    // Don't forget to set the corresponding value to FALSE after processing

    pinSet_last = pinSet_now; 

    pinUp_last = pinUp_now; 

    pinDown_last = pinDown_now; 

}

Then use the timer interrupt to execute a key_scan() function every 20ms.