Arduino008_Serial Output

Serial communication is the process of sending data one bit at one time, sequentially, over a communication channel or computer bus.

The data rate is 9600 bits per second (sometimes called 9600 baud), the receiver will continually read the voltage that the sender is putting out, and every 1/9600th of a second, it will interpret that voltage as a new bit of data. If the voltage is high (+5V in the case of Wiring/Arduino, the PIC, and BX-24), it will interpret that bit of data as a 1. If it is low (0V in the case of Wiring/Arduino, the PIC, and BX-24), it will interpret that bit of data as a 0.

Byte is a code. The BYTE modifier doesn’t format the bytes. It sends out the raw binary value of the byte. The Serial Monitor receives that binary value and assumes it should show you the ASCII (http://www.asciitable.com/) character corresponding to that value. The garbage characters are characters corresponding to the ASCII values the Monitor is receiving.

Also can use Tom Gerhardt’s serial application, Cornflake (http://tomgerhardt.com/Cornflake/).

1 byte = 8 bits

println 255 = begin 2 5 5 end =  5 byte

Material Parts – I use potentiometer as output sensor.

Step 1 – import the processing serial library

Download

Processing Library: processing-arduino-0017.zip (Updated 22 Sept. 2009)

Instructions

1. Unzip the library and copy the “arduino” folder into the “libraries” sub-folder of your Processing Sketchbook. (You can find the location of your    Sketchbook by opening the Processing Preferences. If you haven’t made a “libraries” sub-folder, create one.)
2. Run Arduino, open the Examples > Firmata > StandardFirmata sketch, and upload it to the Arduino board.
3. Configure Processing for serial: http://processing.org/reference/libraries/serial/
4. In Processing, open one of the examples that comes with with the Arduino library.
5. Edit the example code to select the correct serial port.
6. Run the example.

Step 2 – Graph the sensor’s values

By communicating with Processing, always need to read value in BYTE instead of DEC. Otherwise, the graph will go wrong like the graphing image below:

Failed exercise by reading the value in DEC.

Correct exercise by reading the value in BYTE

Code in Arduino:

int analogPin = 0;

int analogValue = 0;

void setup() {

Serial.begin(9600);

}

void loop() {

analogValue = analogRead(analogPin);

analogValue = analogValue/4;

Serial.println(analogValue, BYTE);

delay (10);

}

Code in Processing:

import processing.serial.*;

Serial myPort;  //the serial port

int graphXPos = 0;  //the horizontal position of the graph

void setup() {

size (400,300);  //window size

println(Serial.list());

myPort = new Serial(this, Serial.list()[0], 9600);    //to open the port number[0]

background (198,232,239);    //background color

}

void draw() {     //nothing happen in draw becuase it happens in SerialEvent()

}

void serialEvent (Serial myPort) {     //every time a new byte arrives int he serial port, serialEvent() called

int inByte = myPort.read();     //get the byte // myPort.read() tells the program to read a byte from the serial port myPort.

println(inByte);     //print it

//to draw a graph with byte that reads

stroke(249,111,8);     //line color

line(graphXPos, height, graphXPos, height – inByte);     // draw the line

//at the edge of the screen, go back to the beginning

if (graphXPos >= width) {

graphXPos = 0;

background(198,232,239);     // clear the screen

}

else {

graphXPos++; // increment the horizontal position for the next reading

}

}