Learning Processing: Chapter 19: Example 19-8: Reading from Serial Port

Example

// Learning Processing
// Daniel Shiffman
// http://www.learningprocessing.com

// Example 19-8: Reading from serial port

import processing.serial.*;

int val = 0; // To store data from serial port, used to color background
Serial port; // The serial port object

void setup() {
  size(200,200);
  
  // In case you want to see the list of available ports
  // println(Serial.list());
  
  // Using the first available port (might be different on your computer)
  port = new Serial(this, Serial.list()[0], 9600); 
}

void draw() {
  // The serial data is used to color the background.   
 background(val); 
}

// Called whenever there is something available to read
void serialEvent(Serial port) {
  // Data from the Serial port is read in serialEvent() using the read() function and assigned to the global variable: val
  val = port.read();
  // For debugging
  // println( "Raw Input:" + val);
}

Comments (7)

Jessica

I tried to get two computers to talk to each other through the serial port using Processing. However, It hasn’t worked. I tried this book and you had this example. I couldn’t find where the +input was coming from for the debugging statement inside the serialEvent(). I don’t think that the serialEvent() function is getting called. If you have any tips on this, that would be great.
http://www.learningprocessing.com Daniel Shiffman

You may want to consider looking at the networking client/server examples for communication between machines as well. Otherwise, it’s hard to know why it isn’t working, perhaps use a console / terminal to make sure your serial ports and working and data is flowing before wondering if it’s an issue with your Processing code.
Logictom

I believe
// println( “Raw Input:” + input);
in serialEvent should be:
// println( “Raw Input:” + val);
Unless input is some Prcoessing defined variable? (Only been using Processing < 1hr )
http://www.learningprocessing.com Daniel Shiffman

Whoops, that’s right! Going to correct it now, thank you!
Talib

hello
i hope u can help me how to read and save from serial port from the first step.
ersinful

Hi,
how can i send two variables from arduino to processing ?
timshi thakkar

#include

#define MEM_SIZE 512

int trigger_value; // pressure reading threshold for identifying a bike is pressing.

int threshold = 200; //change this amount if necessary. tunes sensitivity.

int the_tally; //total amount of sensings.

int incomingByte = 0; // for incoming serial data

int the_time_offset; // in case of power out, it starts counting time from when the power went out.

int latest_minute;

int the_wheel_delay = 50; //number of milliseconds to create accurate readings for cars. prevents bounce.

int car_timeout = 3000;

long the_wheel_timer; //for considering that double wheel-base of cars, not to count them twice.

int the_max = 0;

int is_measuring = 0;

int count_this = 0;

int strike_number = 0;

float wheel_spacing = 2.7500; //average spacing between wheels of car (METERS)

float first_wheel = 0.0000000;

float second_wheel= 0.0000000;

float wheel_time = 0.0000000;

float the_speed = 0.0000000;

int time_slot;

int speed_slot;

int all_speed;

void setup() {

pinMode(A3, INPUT);

pinMode(13, OUTPUT);

pinMode(A2,OUTPUT);

pinMode(A4,OUTPUT);

digitalWrite(A4,LOW);

digitalWrite(A2,HIGH);

Serial.begin(9600);

//EEPROM.read(0, the_tally); //the tally is stored in position 0. assigns the read value to ‘the_tally’.

//EEPROM.read((the_tally*2)+1, the_time_offset); //read the last time entry

if(the_tally trigger_value) {

if (strike_number == 0 && is_measuring == 0) { // FIRST HIT

Serial.println(“”);

Serial.println(“Car HERE. “);

first_wheel = millis();

is_measuring = 1;

}

if (strike_number == 1 && is_measuring == 1) { // SECOND HIT

Serial.println(“Car GONE.”);

second_wheel = millis();

is_measuring = 0;

}

}

//2 – TUBE IS STILL PRESSURIZED

while(analogRead(A3) > the_max && is_measuring == 1) { //is being pressed, in all cases. to measure the max pressure.

the_max = analogRead(A2);

}

//3 – TUBE IS RELEASED

if (analogRead(A3) the_wheel_delay)) {

strike_number = 1;

}

if (strike_number == 1 && is_measuring == 0 && (millis() – second_wheel > the_wheel_delay) ){

count_this = 1;

}

}

//4 – PRESSURE READING IS ACCEPTED AND RECORDED

if ((analogRead(A3) car_timeout) && is_measuring == 1))

{ //has been released for enough time.

the_tally++;

EEPROM.write(0, the_tally); //puts the value of x at the 0 address.

digitalWrite(13,HIGH);

time_slot = the_tally*2;

speed_slot = (the_tally*2)+1;

Serial.print(“Pressure Reached = “);

Serial.println(the_max);

Serial.print(“Current Count = “);

Serial.println(the_tally);

Serial.print(“time between wheels = “);

wheel_time = ((second_wheel – first_wheel)/3600000);

Serial.println(wheel_time);

int time = ((millis()/1000)/60) + the_time_offset + 1; // the number of seconds since first record.

Serial.println(“time passed =”);

Serial.println(time);

Serial.println(millis()/1000);

EEPROM.write(time_slot, time); //puts the value of y at address ‘the_tally’.

the_speed = (wheel_spacing/1000)/wheel_time;

if (the_speed > 0 ) {

Serial.print(“Estimated Speed (km/h) = “);

Serial.println(the_speed);

EEPROM.write(speed_slot, int(the_speed)); //puts the value of y at address ‘the_tally’.

}

else {

Serial.println(“Speed not measureable”);

EEPROM.write(speed_slot, 0); //puts the value of y at address ‘the_tally’.

}

//RESET ALL VALUES

the_max = 0;

strike_number = 0;

count_this = 0;

is_measuring = 0;

digitalWrite(13,LOW);

} //4 ends

if (Serial.available() > 0) {

// read the incoming byte:

incomingByte = Serial.read();

if (incomingByte == ’1′) {

print_memory();

}

if (incomingByte == ’2′) {

Serial.println(“”);

Serial.println(“ARE YOU SURE YOU WANT TO ERASE THE MEMORY? Enter Y/N”);

}

if (incomingByte == ‘N’ || incomingByte == ‘n’) {

Serial.println(“MEMORY ERASE CANCELLED”);

Serial.println(“___________________________________________________”);

}

if (incomingByte == ‘Y’ || incomingByte == ‘y’) {

erase_memory();

print_memory();

}

if (incomingByte == ’3′) {

process();

}

//if ends

} //serial available ends

} //loop ends

void print_memory() {

if (the_tally > 0) {

Serial.println(“”);

Serial.println(“Count , Time (Minutes) , Speed (km/h)”);

for (int i=1; i<= the_tally; i++){

Serial.print(i);

Serial.print(" , ");

long y = EEPROM.read(2*i);

Serial.print(y);

Serial.print(" , ");

long z = EEPROM.read((2*i)+1);

Serial.println(z);

all_speed = (all_speed+z); //add all the speeds together to find average.

latest_minute = y;

} //for ends

}//if ends

Serial.println("");

Serial.print("Total Cars, ");

Serial.println(the_tally);//read memory

Serial.print("Total Minutes Measured, ");

Serial.println(latest_minute);

Serial.print("Traffic Rate (cars per min), ");

if ((the_tally/latest_minute) <= 0) {

Serial.println("0");

}

else {

Serial.println(the_tally/latest_minute);

}

Serial.print("Average Car Speed (km per hour), ");

if ((all_speed/the_tally) <= 0) {

Serial.println("0");

}

else {

Serial.println(all_speed/the_tally);

}

Serial.println("___________________________________________________");

} //print memory ends

void erase_memory() {

//erase current tally

Serial.println("");

Serial.println("ERASING MEMORY …");

for (int i = 0; i <= MEM_SIZE; i++){

EEPROM.write(i, 0);

}

the_tally = 0;

the_time_offset = 0;

latest_minute = 0;

}

void process()

{

//Serial.println("Count , Time (Minutes)");

for (int i=1; i<= the_tally; i++){

Serial.println(i);

long y = EEPROM.read(2*i);

Serial.println(y);}

}

this is my program for cars counting …

import processing.serial.*;

Serial myPort; // The serial port

int xPos = 1;

int the_tally; //data received from serial port

void setup () {

// set the window size:

size(400, 300);

myPort = new Serial(this, "COM3", 9600);

// don't generate a serialEvent() unless you get a newline character:

myPort.bufferUntil('n');

// set inital background:

background(0);

}

void draw () {

// everything happens in the serialEvent()

}

void serialEvent (Serial myPort) {

for(int i=1;i= width) {

xPos = 0;

background(0);

}

else {

// increment the horizontal position:

xPos++;

}

}

}

this is my processing code… but its noit displaying anything on the window can you help me out? i want to display no.of cars vs time….