This example demonstrates multi-byte communication from the Arduino or Genuino board to the computer using a call-and-response (handshaking) method.
This sketch sends an ASCII A (byte of value 65) on startup and repeats that until it gets a serial response from the computer. Then it sends three sensor values as single bytes, and waits for another response from the computer.
You can use the Arduino Software (IDE) serial monitor to view the sent data, or it can be read by Processing (see code below), Flash, PD, Max/MSP (see example below), etc.
Arduino or Genuino Board 2 analog sensors (potentiometer, photocell, FSR, etc.) pushbutton 3 10K ohm resistors hook-up wires breadboard Software Required
Processing or Max/MSP version 5 Circuit
Connect analog sensors to analog input pin 0 and 1 with 10K ohm resistors used as voltage dividers. Connect a pushbutton or switch to digital I/O pin 2 with a 10K ohm resistor as a reference to ground.
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image developed using Fritzing. For more circuit examples, see the Fritzing project page
Schematic
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/* 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 sketch to run with this example:
// 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 // if using Processing 2.1 or later, use Serial.printArray() 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; } } }
Processing Code
Copy the Processing sketch from the code sample above. As you change the value of the analog sensor, you'll get a ball moving onscreen something like this. The ball will appear only when you push the button: