Lesson 3--Microduino "Button Controlled LED"

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Objective

The first two lessons showed you how to use software to control the LED directly. If we add a button to control the LED light, then we can combine the use of both hardware and software. Previously, we used Microduino I/O port as the output to control the LED. So if we want to use a button, how would we monitor when it is pressed? In this lesson, we will use a button as an example to show how to use Microduino as an input.

Equipment

  • Microduino-Core
  • Microduino-FT232R
  • Other hardware equipment
    • 1x Box of breadboard jumper wires
    • 1x Breadboard
    • 1x LED (Light-Emitting Diode)
    • 1x 220ohm resistor
    • 1x Button
    • 1x USB Data cable

Button

  • Button principle
Button.jpg
  • Button connection
Button connection.jpg

Experiment Schematic

Button schematic.jpg

Using the external pulldown method, when the button is unpressed, the input to D2 is "LOW". When pressed, it is "HIGH".

Program

  • LED is on while button is pressed down
const int buttonPin = 2;     // Define button input pin
const int ledPin =  11;     //Define LED pin
int buttonState = 0;        //Initialize the button value
void setup() {
  pinMode(ledPin, OUTPUT);    //Set the LED pin as output    
  pinMode(buttonPin, INPUT);  //Set button pin as input    
}
void loop(){
  buttonState = digitalRead(buttonPin);//Read the value from the buttonPin
  if (buttonState == HIGH) {     
    digitalWrite(ledPin, HIGH); //If the button input signal is high, the LED will light up
  } 
  else {
    digitalWrite(ledPin, LOW); //LED goes out
  }
}
  • LED voltage flip
const int buttonPin = 2;     // Define button input pin
const int ledPin =  11;     

int buttonState = 0; 
boolean led;         //Define LED as boolean(true or false)
void setup() {
  pinMode(ledPin, OUTPUT);      
  // pinMode(buttonPin, INPUT); //Set the button pin as input     
  pinMode(buttonPin, INPUT);//Set button pin as input    
}
void loop(){
  buttonState = digitalRead(buttonPin);
  if (buttonState ==HIGH)
  {  
    delay(200);                   //Short time delay for stabilization
    // delay(1000);               //Long time press
    // if (buttonState == LOW)    //Check still is low
    led=!led;                     //LED state flip
  } 
  digitalWrite(ledPin, led);  
}

digitalRead() usage

Read a pin's value and return HIGH or LOW.

Result

  • Program 1: LED is on while button is pressed down.
  • Program 2: Each time you press the button, the LED will turn on/off.

Video