Tutorial.SerialCallResponseASCII History

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May 02, 2012, at 04:09 PM by Scott Fitzgerald -
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November 16, 2011, at 04:15 AM by Scott Fitzgerald -
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September 23, 2010, at 10:26 PM by Christian Cerrito -
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Serial Call and Response (handshaking) with ASCII-encoded output

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Serial Call and Response (handshaking) with ASCII-encoded output

September 23, 2010, at 10:25 PM by Christian Cerrito -
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September 17, 2010, at 09:23 PM by Tom Igoe -
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An example of string-based communication from the Arduino board to the computer using a call-and-response (handshaking) method.

This program sends an ASCII string on startup and repeats that until it gets a serial response from the computer. Then it sends three sensor values as ASCII-encoded numbers, separated by commas and terminated by a linefeed and carriage return, and waits for another response from the computer.

to:

This example demonstrates string-based communication from the Arduino board to the computer using a call-and-response (handshaking) method.

The sketch sends an ASCII string on startup and repeats that until it gets a serial response from the computer. Then it sends three sensor values as ASCII-encoded numbers, separated by commas and terminated by a linefeed and carriage return, and waits for another response from the computer.

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Compare this to the Serial call and response example. They are similar, in that both use a handshaking method, but this one encodes the sensor readings as strings, while the other sends them as binary values. While sending as ASCII-encoded strings takes more bytes, it means you can easily send values larger than 255 for each sensor reading.

to:

Compare this to the Serial call and response example. They are similar, in that both use a handshaking method, but this one encodes the sensor readings as strings, while the other sends them as binary values. While sending as ASCII-encoded strings takes more bytes, it means you can easily send values larger than 255 for each sensor reading. It's also easier to read in a serial terminal program.

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Analog sensors 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 10Kohm resistors used as voltage dividers. Connect a pushbutton or switch connected to digital I/O pin 2 with a 10Kohm resistor as a reference to ground.

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Schematic

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Schematic

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/*  
 Serial Call and Response in ASCII 
 Language: Processing

 Reads in a string of characters from a serial port until 
 it gets a linefeed (ASCII 10).  Then splits the string into 
 sections separated by commas. Then converts the sections to ints, 
 and prints them out.

 created 2 Jun 2005
 modified 14 Apr 2009
 by Tom Igoe

This example code is in the public domain.
 */

import processing.serial.*;     // import the Processing serial library
Serial myPort;                  // The serial port

float bgcolor;			// Background color
float fgcolor;			// Fill color
float xpos, ypos;	        // Starting position of the ball

void setup() {
  size(640,480);

  // List all the available serial ports
  println(Serial.list());

  // I know that the first port in the serial list on my mac
  // is always my  Arduino module, so I open Serial.list()[0].
  // Change the 0 to the appropriate number of the serial port
  // that your microcontroller is attached to.
  myPort = new Serial(this, Serial.list()[0], 9600);

  // read bytes into a buffer until you get a linefeed (ASCII 10):
  myPort.bufferUntil('\n');

  // draw with smooth edges:
  smooth();
}

void draw() {
  background(bgcolor);
  fill(fgcolor);
  // Draw the shape
  ellipse(xpos, ypos, 20, 20);
}

// serialEvent  method is run automatically by the Processing applet
// whenever the buffer reaches the  byte value set in the bufferUntil() 
// method in the setup():

void serialEvent(Serial myPort) { 
  // read the serial buffer:
  String myString = myPort.readStringUntil('\n');
  // if you got any bytes other than the linefeed:
    myString = trim(myString);

    // split the string at the commas
    // and convert the sections into integers:
    int sensors[] = int(split(myString, ','));

    // print out the values you got:
    for (int sensorNum = 0; sensorNum < sensors.length; sensorNum++) {
      print("Sensor " + sensorNum + ": " + sensors[sensorNum] + "\t"); 
    }
    // add a linefeed after all the sensor values are printed:
    println();
    if (sensors.length > 1) {
      xpos = map(sensors[0], 0,1023,0,width);
      ypos = map(sensors[1], 0,1023,0,height);
      fgcolor = sensors[2];
    }
    // send a byte to ask for more data:
    myPort.write("A");
  }

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 and paste it into a new Max window

September 16, 2010, at 10:14 PM by Tom Igoe -
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August 27, 2010, at 09:03 AM by Christian Cerrito -
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August 27, 2010, at 09:03 AM by Christian Cerrito -
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  • Serial Call and Response ASCII - send multiple vairables using a call-and-response (handshaking) method, and ASCII-encoding the values before sending.
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August 27, 2010, at 08:57 AM by Christian Cerrito -
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  • Analog inputs connected to analog input pin 0 and 1.
  • Switch connected to digital I/O 2.
to:

Analog sensors 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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See Also:

August 27, 2010, at 08:55 AM by Christian Cerrito -
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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
February 23, 2010, at 11:39 PM by Tom Igoe -
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 /*
   Serial Call and Response in ASCII
  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 ASCII-encoded, comma-separated sensor values, 
  truncated by a linefeed and carriage return, 
  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/SerialCallResponseASCII
  
  Created 26 Sept. 2005
  by Tom Igoe
  Modified 14 April 2009
  by Tom Igoe and Scott Fitzgerald
  */
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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
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 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 
 }
to:
 Reads in a string of characters from a serial port until 
 it gets a linefeed (ASCII 10).  Then splits the string into 
 sections separated by commas. Then converts the sections to ints, 
 and prints them out.
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This example code is in the public domain.

August 27, 2009, at 08:57 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 07:43 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, DEC);
    Serial.print(",");
    Serial.print(secondSensor, DEC);
    Serial.print(",");
    Serial.println(thirdSensor, DEC);               
  }

}

void establishContact() {

  while (Serial.available() <= 0) {
    Serial.println("0,0,0");   // send an initial string
    delay(300);
  }

} @]

Processing Code

[@

June 25, 2009, at 10:50 PM by Tom Igoe -
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[-click the image to enlarge-]

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click the image to enlarge

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Schematic

click the image to enlarge

April 16, 2009, at 07:58 PM by Tom Igoe -
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Analog inputs connected to analog input pin 0 and 1. Switch connected to digital I/O 2.

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

[-click the image to enlarge-]

April 16, 2009, at 12:53 AM by Tom Igoe -
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to:
April 16, 2009, at 12:52 AM by Tom Igoe -
Added lines 1-157:

Examples > Communication

Serial Call and Response (handshaking) with ASCII-encoded output

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

This program sends an ASCII string on startup and repeats that until it gets a serial response from the computer. Then it sends three sensor values as ASCII-encoded numbers, separated by commas and terminated by a linefeed and carriage return, 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. The examples below split the incoming string on the commas and convert the string into numbers again.

Compare this to the Serial call and response example. They are similar, in that both use a handshaking method, but this one encodes the sensor readings as strings, while the other sends them as binary values. While sending as ASCII-encoded strings takes more bytes, it means you can easily send values larger than 255 for each sensor reading.

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, DEC);
    Serial.print(",");
    Serial.print(secondSensor, DEC);
    Serial.print(",");
    Serial.println(thirdSensor, DEC);               
  }
}

void establishContact() {
  while (Serial.available() <= 0) {
    Serial.println("0,0,0");   // send an initial string
    delay(300);
  }
}

Processing Code

/*  
 Serial Call and Response in ASCII 
 Language: Processing

 Reads in a string of characters from a serial port until 
 it gets a linefeed (ASCII 10).  Then splits the string into 
 sections separated by commas. Then converts the sections to ints, 
 and prints them out.

 created 2 Jun 2005
 modified 14 Apr 2009
 by Tom Igoe
 */

import processing.serial.*;     // import the Processing serial library
Serial myPort;                  // The serial port

float bgcolor;			// Background color
float fgcolor;			// Fill color
float xpos, ypos;	        // Starting position of the ball

void setup() {
  size(640,480);

  // List all the available serial ports
  println(Serial.list());

  // I know that the first port in the serial list on my mac
  // is always my  Arduino module, so I open Serial.list()[0].
  // Change the 0 to the appropriate number of the serial port
  // that your microcontroller is attached to.
  myPort = new Serial(this, Serial.list()[0], 9600);

  // read bytes into a buffer until you get a linefeed (ASCII 10):
  myPort.bufferUntil('\n');

  // draw with smooth edges:
  smooth();
}

void draw() {
  background(bgcolor);
  fill(fgcolor);
  // Draw the shape
  ellipse(xpos, ypos, 20, 20);
}

// serialEvent  method is run automatically by the Processing applet
// whenever the buffer reaches the  byte value set in the bufferUntil() 
// method in the setup():

void serialEvent(Serial myPort) { 
  // read the serial buffer:
  String myString = myPort.readStringUntil('\n');
  // if you got any bytes other than the linefeed:
    myString = trim(myString);

    // split the string at the commas
    // and convert the sections into integers:
    int sensors[] = int(split(myString, ','));

    // print out the values you got:
    for (int sensorNum = 0; sensorNum < sensors.length; sensorNum++) {
      print("Sensor " + sensorNum + ": " + sensors[sensorNum] + "\t"); 
    }
    // add a linefeed after all the sensor values are printed:
    println();
    if (sensors.length > 1) {
      xpos = map(sensors[0], 0,1023,0,width);
      ypos = map(sensors[1], 0,1023,0,height);
      fgcolor = sensors[2];
    }
    // send a byte to ask for more data:
    myPort.write("A");
  }

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:

Max Code

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

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