serial-port - Arduino map() 方法 - 为什么？

Question

我只是在看一些示例代码并遇到了一行，我不完全理解为什么需要这样做。我了解您正在接受模拟值。这个值显然在 0 到 1024 之间？为什么是这样？为什么输出需要映射在 0 到 255 之间？是什么决定了这里使用的参数？有问题的行:

   // map it to the range of the analog out:
      outputValue = map(sensorValue, 0, 1024, 0, 255); 

在代码中突出显示:

created 29 Dec. 2008
 Modified 4 Sep 2010
 by Tom Igoe

 This example code is in the public domain.

 */

// These constants won't change.  They're used to give names
// to the pins used:
const int analogInPin = A0;  // Analog input pin that the potentiometer is attached to
const int analogOutPin = 9; // Analog output pin that the LED is attached to

int sensorValue = 0;        // value read from the pot
int outputValue = 0;        // value output to the PWM (analog out)

void setup() {
  // initialize serial communications at 9600 bps:
  Serial.begin(9600); 
}

void loop() {
  // read the analog in value:
  sensorValue = analogRead(analogInPin);            
  **// map it to the range of the analog out:
  outputValue = map(sensorValue, 0, 1024, 0, 255);**  
  // change the analog out value:
  analogWrite(analogOutPin, outputValue);           

  // print the results to the serial monitor:
  Serial.print("sensor = " );                       
  Serial.print(sensorValue);      
  Serial.print("\t output = ");      
  Serial.println(outputValue);   

  // wait 10 milliseconds before the next loop
  // for the analog-to-digital converter to settle
  // after the last reading:
  delay(10);                     
}

非常感谢您的回复。

Answer 1

模拟输出只有一个介于 0 和 255 之间的可接受范围。

因此，该值必须映射在可接受的范围内。

map 方法的文档在这里:http://arduino.cc/en/Reference/map

Because the Arduino has an analogRead resolution of 0-1023, and an analogWrite resolution of only 0-255, this raw data from the potentiometer needs to be scaled before using it...

此解释来自 Arduino 传感器教程(在“代码”标题下):http://arduino.cc/en/Tutorial/AnalogInOutSerial