ESP32-Arduino（三）GPIO输入操作，去抖，ADC多按键

GPIO除了输入输出，一般还有很丰富的复用功能，以ESP32为例：

我们在上次开关量输出（HIGH/LOW）先来看输入信号一般的用法：

1. 读取外部接口状态--开关信号量，比如按键

2. 模拟输入， 读取外部信号的电压值

3. 用作中断触发，当状态改变时触发中断，进入预设的处理程序

GPIO其他的输出功能：

1. DAC/PWM

然后就是组合的高速串口接口了，SPI/I2C最为典型，和通用串口的差异就在于支持高速的数据传输，而且主要以同步传输为主（带时钟信号）。

我们这一节主要来看输入的应用，主要三个案例：

1. 读取状态；

2. 增加去抖动处理，提高可靠性

3. 通过模拟输入实现一个IO处理多个按键

4.*触发外部中断

案例1，读取光电开关状态，并控制LED

初级，直接控制状态

/*
  GPIO digital input. 
  P12 connected to an optical switch.
  
*/
#define LED_ON LOW
#define LED_OFF HIGH

#define SWITCH_ON HIGH
#define SWITCH_OFF LOW

// These constants won't change. They're used to give names to the pins used:
const int switchInput=12;
const int led=22;


int switchState ;        // value read from the pot



void setup() {
  // initialize serial communications at 9600 bps:
 
  pinMode(switchInput,INPUT);
  pinMode(led,OUTPUT);
}

void loop() {
  // read the analog in value:
  switchState=digitalRead(switchInput);
  if(switchState==SWITCH_ON) digitalWrite(led,LED_ON);
  
  else digitalWrite(led,LED_OFF);
    

  delay(2);
}

案例2  .升级，加入去抖

/*
  GPIO digital input. 
  P12 connected to an optical switch.
  
*/
#define LED_ON LOW
#define LED_OFF HIGH


#define SWITCH_ON HIGH
#define SWITCH_OFF LOW

// These constants won't change. They're used to give names to the pins used:
const int switchInput=12;
const int led=22;


int switchState = SWITCH_OFF;        // value read from the pot

int lastState=SWITCH_OFF;
int ledState=LED_OFF;

unsigned long lastDebounceTime = 0;  // the last time the output pin was toggled
unsigned long debounceDelay = 50;    // the debounce time; increase if the output flickers


void setup() {
  // initialize serial communications at 9600 bps:
  Serial.begin(9600);
  pinMode(switchInput,INPUT);
  pinMode(led,OUTPUT);
  digitalWrite(led,ledState);
}

void loop() {
  // read the analog in value:
  int readValue=digitalRead(switchInput);
  if(readValue!=lastState){
    // reset the debounce timer
    lastDebounceTime=millis();
    }
   if((millis()-lastDebounceTime)>debounceDelay){
    // longer than limit,set the actual state
    if(readValue!=switchState){
      
      switchState=readValue;
    
      if(switchState==SWITCH_ON){
        ledState=!ledState;
        Serial.println("led stat changed.");
      }
    }
  }
  digitalWrite(led,ledState);
  // save the read value.
   lastState=readValue;
}

关键Arduino库函数： millis(), digitalRead()

millis() - Arduino Reference

digitalRead() - Arduino Reference

案例3， 一个GPIO通过读取模拟信号量来获取多个控制按键

电路连接的原理

代码

// These constants won't change. They're used to give names to the pins used:
const int analogInPin = 12;  // Analog input pin that the potentiometer is attached to
const int led = 22; // Analog output pin that the LED is attached to

int sensorValue = 0;        // value read from the pot


void setup() {
  // initialize serial communications at 9600 bps:
  Serial.begin(9600);
}

void loop() {
  // read the analog in value:
  sensorValue = analogRead(analogInPin);

  // print the results to the Serial Monitor:
  Serial.print("sensor = ");
  Serial.print(sensorValue);
  Serial.print("\n ");
 

  // wait 2 milliseconds before the next loop for the analog-to-digital
  // converter to settle after the last reading:
  delay(2);
}

时间关系， 留给大家思考的题目： 

1. 怎么分辨多按键？ 

2. 怎么进行滤波处理？ 

3. 能否处理组合键？ 

4. 如何处理按下和释放？ 

Micropython的示例代码：

import machine
from machine import ADC,Pin
import time

led=machine.Pin(22,machine.Pin.OUT)

adc=ADC(Pin(33))

while True:
    
    adcValue=adc.read()
    
    print("voltage: %d mv \r\n"%(adcValue))
    time.sleep(0.1)