對話是溝通的開始，你講你的英文我講我的拉丁文，牛頭不對馬嘴這樣是不行的。
除了你講的我能懂，我講的你也能懂之外，還要建立起彼此間說話的規則，否則你一句我也來一句，這樣有講等於沒講。
另外一點是，兩個人說話總有一方先起頭，另一方才隨後附和，所以就變成有主從關係。通常主方會持續發出「我想和你說話，你知道了嗎？如果知道了，那麼我可以開始說了嗎？」類似這樣的訊息，而從方則會持續發出「你是在跟我說話嗎？如果是的話那麼你可以開始說了。」類似這樣的訊息。
想要讓 Arduino 和 Processing 這兩個軟體彼此有良好的溝通，也必須透過上述所講的方式進行。
本文示範讓 Arduino 和 電腦端的 Processing 互傳多字節資料。一開始 Arduino 會先持續傳送一個 ASCII 碼 'A' 給 Processing，直到 Processing 有了回應，Arduino 才會繼續後續的動作。
你可以利用連接在 Arduino 上面的兩個電位器移動電腦上的小白點，也可以按下按鈕讓小白點消失或是出現。
原文 http://arduino.cc/en/Tutorial/SerialCallResponse
電路圖
Arduino Code
/*
Serial Call and Response
Language: Wiring/Arduino
This program sends an ASCII A (byte of value 65) on startup
and repeats that until it gets some data in.
Then it waits for a byte in the serial port, and
sends three sensor values whenever it gets a byte in.
Thanks to Greg Shakar and Scott Fitzgerald for the improvements
The circuit:
* potentiometers attached to analog inputs 0 and 1
* pushbutton attached to digital I/O 2
Created 26 Sept. 2005
by Tom Igoe
modified 24 April 2012
by Tom Igoe and Scott Fitzgerald
This example code is in the public domain.
http://www.arduino.cc/en/Tutorial/SerialCallResponse
*/
int firstSensor = 0; // first analog sensor
int secondSensor = 0; // second analog sensor
int thirdSensor = 0; // digital sensor
int inByte = 0; // incoming serial byte
void setup()
{
// start serial port at 9600 bps:
Serial.begin(9600);
while (!Serial) {
; // wait for serial port to connect. Needed for Leonardo only
}
pinMode(2, INPUT); // digital sensor is on digital pin 2
establishContact(); // send a byte to establish contact until receiver responds
}
void loop()
{
// if we get a valid byte, read analog ins:
if (Serial.available() > 0) {
// get incoming byte:
inByte = Serial.read();
// read first analog input, divide by 4 to make the range 0-255:
firstSensor = analogRead(A0)/4;
// delay 10ms to let the ADC recover:
delay(10);
// read second analog input, divide by 4 to make the range 0-255:
secondSensor = analogRead(1)/4;
// read switch, map it to 0 or 255L
thirdSensor = map(digitalRead(2), 0, 1, 0, 255);
// send sensor values:
Serial.write(firstSensor);
Serial.write(secondSensor);
Serial.write(thirdSensor);
}
}
void establishContact() {
while (Serial.available() <= 0) {
Serial.print('A'); // send a capital A
delay(300);
}
}
Processing Code
// This example code is in the public domain.
import processing.serial.*;
int bgcolor; // Background color
int fgcolor; // Fill color
Serial myPort; // The serial port
int[] serialInArray = new int[3]; // Where we'll put what we receive
int serialCount = 0; // A count of how many bytes we receive
int xpos, ypos; // Starting position of the ball
boolean firstContact = false; // Whether we've heard from the microcontroller
void setup() {
size(256, 256); // Stage size
noStroke(); // No border on the next thing drawn
// Set the starting position of the ball (middle of the stage)
xpos = width/2;
ypos = height/2;
// Print a list of the serial ports, for debugging purposes:
println(Serial.list());
// I know that the first port in the serial list on my mac
// is always my FTDI adaptor, so I open Serial.list()[0].
// On Windows machines, this generally opens COM1.
// Open whatever port is the one you're using.
String portName = Serial.list()[0];
myPort = new Serial(this, portName, 9600);
}
void draw() {
background(bgcolor);
fill(fgcolor);
// Draw the shape
ellipse(xpos, ypos, 20, 20);
}
void serialEvent(Serial myPort) {
// read a byte from the serial port:
int inByte = myPort.read();
// if this is the first byte received, and it's an A,
// clear the serial buffer and note that you've
// had first contact from the microcontroller.
// Otherwise, add the incoming byte to the array:
if (firstContact == false) {
if (inByte == 'A') {
myPort.clear(); // clear the serial port buffer
firstContact = true; // you've had first contact from the microcontroller
myPort.write('A'); // ask for more
}
}
else {
// Add the latest byte from the serial port to array:
serialInArray[serialCount] = inByte;
serialCount++;
// If we have 3 bytes:
if (serialCount > 2 ) {
xpos = serialInArray[0];
ypos = serialInArray[1];
fgcolor = serialInArray[2];
// print the values (for debugging purposes only):
println(xpos + "\t" + ypos + "\t" + fgcolor);
// Send a capital A to request new sensor readings:
myPort.write('A');
// Reset serialCount:
serialCount = 0;
}
}
}
