arduino ibox项目实战23－Calibration实验

armeasy

硬件平台：PC机一台，ibox卡片电脑一只，arduino扩展板一个，电位器一个，LED灯一个

软件平台：WIN7操作系统，android4.0或android4.4系统

实验目标：通过ADC从电位器读取ADC的值，然后通过得到的值控制LED灯的亮度。

打开arduino的IDE开发工具，依次点击文件->示例-> 03.Analog->AnalogWriteMega，AnalogWriteMega的示例程序将会被打开，其源码如下：

1. const int sensorPin = A0;    // pin that the sensor is attached to
   
2. const int ledPin = PWM0;        // pin that the LED is attached to
   
3. 
   
4. // variables:
   
5. int sensorValue = 0;         // the sensor value
   
6. int sensorMin = 1023;        // minimum sensor value
   
7. int sensorMax = 0;           // maximum sensor value
   
8. 
   
9. 
   
10. void setup() {
    
11.   // turn on LED to signal the start of the calibration period:
    
12.   pinMode(LED1, OUTPUT);
    
13.   digitalWrite(LED1, HIGH);
    
14. 
    
15.   // calibrate during the first five seconds
    
16.   while (millis() < 5000) {
    
17.     sensorValue = analogRead(sensorPin);
    
18. 
    
19.     // record the maximum sensor value
    
20.     if (sensorValue > sensorMax) {
    
21.       sensorMax = sensorValue;
    
22.     }
    
23. 
    
24.     // record the minimum sensor value
    
25.     if (sensorValue < sensorMin) {
    
26.       sensorMin = sensorValue;
    
27.     }
    
28.   }
    
29. 
    
30.   // signal the end of the calibration period
    
31.   digitalWrite(LED1, LOW);
    
32. }
    
33. 
    
34. void loop() {
    
35.   // read the sensor:
    
36.   sensorValue = analogRead(sensorPin);
    
37. 
    
38.   // apply the calibration to the sensor reading
    
39.   sensorValue = map(sensorValue, sensorMin, sensorMax, 0, 255);
    
40. 
    
41.   // in case the sensor value is outside the range seen during calibration
    
42.   sensorValue = constrain(sensorValue, 0, 255);
    
43. 
    
44.   // fade the LED using the calibrated value:
    
45.   analogWrite(ledPin, sensorValue);
    
46. }

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       将电位器的两端接GND和5V，中间的脚接A0，PWM0接LED，运行程序，通过反复修改程序中的参数，观察LED灯的亮暗程度。