Lesson 4--Microduino "LED Brightness and PWM"

Objective LED has only two states on and off in other three experiment, now through button realize LED brightness light gradually and gradually out That is PWM pulse width modulation. Adjusting digital signal (" 0 ", "1") within a period of time that is the time of the duty ratio, high level "1", the longer and more bright. Detailed information for PWM, please refer to： http://www.geek-workshop.com/thread-125-1-1.html Equipment Microduino-Core Microduino-FT232R Other hardware equipment Breadboard Jumper one box Breadboard one piece LED Light-emitting diodes one 220ohm resistor one Button one USB Data cable one Experimental schematic File:第四课-pwm原理图.jpg 600px Buttons are used with internal pull-up and external pull-down, then connect to the digital I/O port D0-D13. PWM must use I/O port D3,D5,56,D9,D10 and D11. Program int n=0; void setup () { pinMode(2,INPUT); pinMode(7,INPUT_PULLUP);//Set to internal pull-up pinMode(11,OUTPUT);//The PWM only can use I/O port 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：Write the simulation value to the specified pin grammar：analogWrite(pin, val)，pin：Microduino I/O port number；val：values from 0 to 255 Result Left button to make LED brightness progressively decreasing, and the right button to make LED brightness incremental. Video