Tutorial.SerialCallResponse History

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Serial Call and Response (handshaking)

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Serial Call and Response (handshaking)

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An example of multi-byte communication from the Arduino board to the computer using a call-and-response (handshaking) method.

This program 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.

to:

This example demonstrates multi-byte communication from the Arduino 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.

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Analog inputs connected to analog input pin 0 and 1 with 10K ohm resistors used as voltage dividers. Switch/button connected to digital I/O pin 2 with a 10K ohm resistor as a reference to ground.

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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 10Kohm resistor as a reference to ground.

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/** 
 * Serial Call-Response 
 * by Tom Igoe. 
 * 
 * Sends a byte out the serial port, and reads 3 bytes in. 
 * Sets foregound color, xpos, and ypos of a circle onstage
 * using the values returned from the serial port. 
 * Thanks to Daniel Shiffman  and Greg Shakar for the improvements.
 * 
 * Note: This sketch assumes that the device on the other end of the serial
 * port is going to send a single byte of value 65 (ASCII A) on startup.
 * The sketch waits for that byte, then sends an ASCII A whenever
 * it wants more data. 
*
*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;
    }
  }
}

Output

As you change the value of the analog sensor, you'll get a ball moving onscreen something like this. When you turn the switch off, the ball will disappear:

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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. When you turn the switch off, the ball will disappear:

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The max patch looks like this. The text of the patch is linked behind the image.

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The max patch looks like this. Copy the text from the code sample above.

September 16, 2010, at 10:14 PM by Tom Igoe -
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August 27, 2010, at 08:52 AM by Christian Cerrito -
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  • Virtual Color Mixer - send multiple variables from an Arduino to the computer and read them in Processing.
August 27, 2010, at 08:46 AM by Christian Cerrito -
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Hardware Required'

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Hardware Required

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See Also:

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Hardware Required'

  • Arduino Board
  • (2) analog sensors (potentiometer, photocell, FSR, etc.)
  • (1) momentary switch/button
  • (3) 10K ohm resistors
  • breadboard
  • hook-up wire

Software Required

  • Processing or
  • Max/MSP version 5
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Analog inputs connected to analog input pin 0 and 1. Switch connected to digital I/O 2.

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Analog inputs connected to analog input pin 0 and 1 with 10K ohm resistors used as voltage dividers. Switch/button connected to digital I/O pin 2 with a 10K ohm resistor as a reference to ground.

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February 23, 2010, at 11:36 PM by Tom Igoe -
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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
  
  
  http://www.arduino.cc/en/Tutorial/SerialCallResponse
to:
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  Created 26 Sept. 2005
  by Tom Igoe
  Modified 14 April 2009
  by Tom Igoe and Scott Fitzgerald
  */

 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);
   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(0)/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.print(firstSensor, BYTE);
     Serial.print(secondSensor, BYTE);
     Serial.print(thirdSensor, BYTE);               
   }
 }

 void establishContact() {
   while (Serial.available() <= 0) {
     Serial.print('A', BYTE);   // send a capital A
     delay(300);
   }
 }
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  • This example code is in the public domain
August 27, 2009, at 08:56 PM by Tom Igoe -
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image developed using Fritzing. For more circuit examples, see the Fritzing project page

July 05, 2009, at 07:38 PM by Tom Igoe -
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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);
  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(0)/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.print(firstSensor, BYTE);
    Serial.print(secondSensor, BYTE);
    Serial.print(thirdSensor, BYTE);               
  }

}

void establishContact() {

  while (Serial.available() <= 0) {
    Serial.print('A', BYTE);   // send a capital A
    delay(300);
  }

}

@]

Processing Code

[@

June 25, 2009, at 10:51 PM by Tom Igoe -
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Schematic

click the image to enlarge

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click on the image to enlarge

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As you change the value of the analog sensor, you'll get a graph something like this:

to:

As you change the value of the analog sensor, you'll get a ball moving onscreen something like this. When you turn the switch off, the ball will disappear:

April 16, 2009, at 12:42 AM by Tom Igoe -
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 This program 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.
to:

This program 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.

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Examples > Communication

Serial Call and Response (handshaking)

An example of multi-byte communication from the Arduino board to the computer using a call-and-response (handshaking) method.

 This program 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 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.

Circuit

Analog inputs connected to analog input pin 0 and 1. Switch connected to digital I/O 2.

Code


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);
  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(0)/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.print(firstSensor, BYTE);
    Serial.print(secondSensor, BYTE);
    Serial.print(thirdSensor, BYTE);               
  }
}

void establishContact() {
  while (Serial.available() <= 0) {
    Serial.print('A', BYTE);   // send a capital A
    delay(300);
  }
}

Processing Code

/** 
 * Serial Call-Response 
 * by Tom Igoe. 
 * 
 * Sends a byte out the serial port, and reads 3 bytes in. 
 * Sets foregound color, xpos, and ypos of a circle onstage
 * using the values returned from the serial port. 
 * Thanks to Daniel Shiffman  and Greg Shakar for the improvements.
 * 
 * Note: This sketch assumes that the device on the other end of the serial
 * port is going to send a single byte of value 65 (ASCII A) on startup.
 * The sketch waits for that byte, then sends an ASCII A whenever
 * it wants more data. 
 */


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;
    }
  }
}


Output

As you change the value of the analog sensor, you'll get a graph something like this:

Max Code

The max patch looks like this. The text of the patch is linked behind the image.

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