arduino ibox项目实战12－通过内核滴溚实现LED闪烁实验

armeasy

硬件平台：PC机一台，ibox卡片电脑一只，arduino扩展板一个

软件平台：WIN7操作系统，android4.0或android4.4系统

打开arduino的IDE开发工具，依次点击文件->示例->01.Basics->BlinkWithoutDelay，BlinkWithoutDelay的示例程序将会被打开，其源码如下：

1. // constants won't change. Used here to set a pin number :
   
2. const int ledPin =  LED1;      // the number of the LED pin LED1 = 22.
   
3. 
   
4. // Variables will change :
   
5. int ledState = LOW;             // ledState used to set the LED
   
6. 
   
7. // Generally, you shuould use "unsigned long" for variables that hold time
   
8. // The value will quickly become too large for an int to store
   
9. unsigned long previousMillis = 0;        // will store last time LED was updated
   
10. 
    
11. // constants won't change :
    
12. const long interval = 1000;           // interval at which to blink (milliseconds)
    
13. 
    
14. void setup() {
    
15.   // set the digital pin as output:
    
16.   pinMode(ledPin, OUTPUT);
    
17. }
    
18. 
    
19. void loop()
    
20. {
    
21.   // here is where you'd put code that needs to be running all the time.
    
22. 
    
23.   // check to see if it's time to blink the LED; that is, if the
    
24.   // difference between the current time and last time you blinked
    
25.   // the LED is bigger than the interval at which you want to
    
26.   // blink the LED.
    
27.   unsigned long currentMillis = millis();
    
28. 
    
29.   if(currentMillis - previousMillis >= interval) {
    
30.     // save the last time you blinked the LED
    
31.     previousMillis = currentMillis;  
    
32. 
    
33.     // if the LED is off turn it on and vice-versa:
    
34.     if (ledState == LOW)
    
35.       ledState = HIGH;
    
36.     else
    
37.       ledState = LOW;
    
38. 
    
39.     // set the LED with the ledState of the variable:
    
40.     digitalWrite(ledPin, ledState);
    
41.   }
    
42. }

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       本实验和前面的LED灯闪烁实验效果相同，只不过实现的方法不同。前面使用了延时函数，而这里通过millis函数读取系统的当前滴溚，然后再用当前滴溚和前面保存的数据比较，如果相差1000，即1秒，则取反ledState，最终达到LED灯每隔一秒闪烁一次的效果。使用本方法将不占系统资源。