Principle of MCU key debounce-EEWORLD

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From the above figure, we can see that there is a difference between the ideal waveform and the actual waveform. The actual waveform has jitter at the moment of pressing and releasing. The length of the jitter time is related to the mechanical characteristics of the key, generally 5~10ms. Usually we press the key manually and then release it. The stable closure time in this action exceeds 20ms. Therefore, the microcontroller must add a de-jitter operation when detecting whether the keyboard is pressed. There are dedicated de-jitter circuits and dedicated de-jitter chips, but usually we can solve the jitter problem by using software delay method.

\/* Software debounce*/

if (0 == K1 ) //If a key is pressed

{

delay_ms(8); //delay for a while to debounce

if (0 == K1) //If a key is really pressed, it is detected to be in a stable closed state

{

... //What to do after pressing the button

}

while(!K1); // Release detection, if you hold down the button, it will continue in the loop

}

Keywords：MCU Reference address：Principle of MCU key debounce

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