arduino

开关，下拉电阻，板载小灯，按开关灯亮

const int ledPin=13;
const int inputPin=2;
void setup() {
  // put your setup code here, to run once:
  pinMode(ledPin, OUTPUT);
  pinMode(inputPin, INPUT);
  //digitalWrite(inputPin, HIGH);
  Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
  int val=digitalRead(inputPin);
  Serial.println(val);
  if(val==HIGH){
    digitalWrite(ledPin, HIGH);
  }else{
    digitalWrite(ledPin, LOW);
  }

}

 下拉电阻作用，开关不按时，引脚2读的是接地

开关按下，电流从5v，走过开关，走到电阻，走到接地

 

 

开关，上拉电阻，板载小灯，按开关灯亮,这里inputPin读出来的2号引脚一直是high，所以把led关闭。当按下按钮，val读出来变为0，那么把led打开设成1.

const int ledPin=13;
const int inputPin=2;
void setup() {
  // put your setup code here, to run once:
  pinMode(ledPin, OUTPUT);
  pinMode(inputPin, INPUT);
  //digitalWrite(inputPin, HIGH);
  Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
  int val=digitalRead(inputPin);
  Serial.println(val);
  if(val==HIGH){
    digitalWrite(ledPin, LOW);
  }else{
    digitalWrite(ledPin, HIGH);
  }

}

 

 

不用外部上拉电阻，用引脚内置的上拉电阻简化布线配置，按下按钮才会关闭led灯：

关键在一个被设置成输入模式的引脚上，写入high值，自动激活该引脚的电阻，达到2w欧

const int ledPin=13;
const int inputPin=2;

void setup() {
  // put your setup code here, to run once:
  pinMode(ledPin, OUTPUT);
  pinMode(inputPin, INPUT);
  digitalWrite(inputPin, HIGH); //这句，在input上打开内置电阻
  Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
  int val=digitalRead(inputPin);   //按下变为0，不按为1
  Serial.println(val);
  if(val==HIGH){
    digitalWrite(ledPin, HIGH);
  }else{
    digitalWrite(ledPin, LOW);
  }

}

 

 

开关去抖：

const int BUTTON = 2; // the input pin where the
 // pushbutton is connected
int val = 0; // val will be used to store the state
 // of the input pin
int old_val = 0; // this variable stores the previous
 // value of "val"
int state = 0; // 0 = LED off and 1 = LED on
void setup() {
 pinMode(LED, OUTPUT); // tell Arduino LED is an output
 pinMode(BUTTON, INPUT); // and BUTTON is an input
}
void loop(){
  val = digitalRead(BUTTON); // read input value and store it
  // yum, fresh
  // check if there was a transition
  if ((val == HIGH) && (old_val == LOW)){
    state = 1 - state;
    delay(10);
  }
  old_val = val; // val is now old, let's store it
  if (state == 1) {
    digitalWrite(LED, HIGH); // turn LED ON
  } else {
    digitalWrite(LED, LOW);
  }
}