Lesson 4--Microduino "LED Brightness and PWM"

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Objective In the previous three lessons, the LED was either on or off. In this lesson, you will learn how to control an LED's brightness using a button and PWM. PWM stands for pulse width modulation. The circuit adjusts the ratio of digital signals ("0", "1") to create a certain brightness. For example, if there are more 1's (HIGH), then the LED seems brighter. Equipment Microduino-Core Microduino-FT232R Other hardware equipment 1x Box of breadboard jumper wires 1x Breadboard 1x LED 1x 220ohm resistor 1x Button 1x USB Data cable Experiment Schematic One button is connected using internal pull-up and the other using external pull-down. They are then connected to I/O ports D0~D13. For the Microduino-Core, only D3, D5, D6, D9, D10, and D11 support PWM, so the user must connect the LED to one of those ports. Program int n=0; void setup () { pinMode(2,INPUT); pinMode(7,INPUT_PULLUP);//Set to internal pull-up pinMode(11,OUTPUT);//PWM must use I/O ports 3、5、11、9、10、11 } void loop() { int up =digitalRead(2); //Read port 2's state int down = digitalRead(7); //Read port 7's state if (up==HIGH) { n=n+5; if (n>=255) { n=255; } //The max limitation is 255 analogWrite(11,n); //Using PWM control the output of port 11, the range of the variable n is 0-255 delay (300); } if (down==LOW) { n=n-5; if (n<=0) { n=0; } analogWrite(11,n); //Using PWM control the output of port 11, the range of the variable n is 0-255 delay (300); } } AnalogWrite() Usage Usage: Writes the simulation value to the specified pin Parameters: analogWrite(pin, val) pin: Microduino I/O port number val: values from 0 to 255 Result Left button increases LED brightness and right button decreases LED brightness. Video