STM32 key light

STM32 Key development

The basic principle of key scanning

Key signal recognition

​ Generally speaking , One end of the two pins of the key is pulled up to the high level through the resistance , The other end is grounded . stay There is no key press When , The input pin is high , When There are buttons to press , The input pin is low . By repeatedly reading the signal of the key input pin , Then identify the high and low level to judge whether there is a key trigger .

Why shake

​ The low level of the input pin of the key does not mean that the key must be pressed , Maybe it's a jamming signal , therefore , It needs to be processed by de dithering , Filter these interference signals , So as to obtain the real key trigger signal .

How to shake

​ After detecting the low level of the key input pin for the first time , A little delay , Read the pin again , If it is still low , It is confirmed as the key trigger signal ; otherwise , Judged as interference signal , Not to deal with .

GPIO Input level reading HAL Library function

GPIO_PinState  HAL_GPIO_ReadPin( GPIO_TypeDef* GPIOx,  uint16_t GPIO_Pin);

 Parameters 1：GPIOx, Port number , Such as ：GPIOB,GPIOF.
 Parameters 2：GPIO_Pin, Pin number , Such as ：GPIO_PIN_9,GPIO_PIN_12.
 Return value ：GPIO_PinState, The level state of the pin .
    
 Application, for example, ： Judge PC13 Input signal of pin , If high , Will PB9 Pin controlled LED The switch state of the lamp is switched .    
if(HAL_GPIO_ReadPin(GPIOC, GPIO_PIN_13) == GPIO_PIN_SET)  
{
                  
    HAL_GPIO_TogglePin(GPIOB, GPIO_PIN_9);      
}