Project Description: Sending Hex values to an Arduino UNO
This simple tutorial will show you how to send Hexadecimal values from a computer to an Arduino Uno. The "Processing" programming language will be used to send the HEX values from the computer when a mouse button is pressed. The Arduino will use these values to adjust the brightness of an LED.
Learning Objectives
To Send Hexadecimal (Hex) values from a computer to the Arduino
Trigger an action based on the press of a mouse button
Learn to create a simple Computer to Arduino interface
Use Arduino's PWM capabilities to adjust brightness of an LED
/* ================================================================================================================================================== Project: 5 min tutorial: Send Hex from computer to Arduino Author: Scott C Created: 21th June 2015 Arduino IDE: 1.6.4 Website: http://arduinobasics.blogspot.com/p/arduino-basics-projects-page.html Description: Arduino Sketch used to adjust the brightness of an LED based on the values received on the serial port. The LED needs to be connected to a PWM pin. In this sketch Pin 10 is used, however you could use Pin 3, 5, 6, 9, or 11 - if you are using an Arduino Uno. ===================================================================================================================================================== */
byte byteRead; //Variable used to store the byte received on the Serial Port int ledPin = 10; //LED is connected to Arduino Pin 10. This pin must be PWM capable.
voidsetup() { Serial.begin(9600); //Initialise Serial communication with the computer pinMode(ledPin, OUTPUT); //Set Pin 10 as an Output pin byteRead = 0; //Initialise the byteRead variable to zero. }
voidloop() { if(Serial.available()) { byteRead = Serial.read(); //Update the byteRead variable with the Hex value received on the Serial COM port. }
analogWrite(ledPin, byteRead); //Use PWM to adjust the brightness of the LED. Brightness is determined by the "byteRead" variable. }
Processing Sketch
The latest version of the Processing IDE can be downloaded here.
/* ================================================================================================================================================== Project: 5 min tutorial: Send Hex from computer to Arduino Author: Scott C Created: 21th June 2015 Processing IDE: 2.2.1 Website: http://arduinobasics.blogspot.com/p/arduino-basics-projects-page.html Description: Processing Sketch used to send HEX values from computer to Arduino when the mouse is pressed. The alternating values 0xFF and 0x00 are sent to the Arduino Uno to turn an LED on and off. You can send any HEX value from 0x00 to 0xFF. This sketch also shows how to convert Hex strings to Hex numbers. ===================================================================================================================================================== */
import processing.serial.*; //This import statement is required for Serial communication
Serial comPort; //comPort is used to write Hex values to the Arduino boolean toggle = false; //toggle variable is used to control which hex variable to send String zeroHex = "00"; //This "00" string will be converted to 0x00 and sent to Arduino to turn LED off. String FFHex = "FF"; //This "FF" string will be converted to 0xFF and sent to Arduino to turn LED on.
voidsetup(){ comPort = new Serial(this, Serial.list()[0], 9600); //initialise the COM port for serial communication at a baud rate of 9600. delay(2000); //this delay allows the com port to initialise properly before initiating any communication. background(0); //Start with a black background.
}
voiddraw(){ //the draw() function is necessary for the sketch to compile //do nothing here //even though it does nothing. }
voidmousePressed(){ //This function is called when the mouse is pressed within the Processing window. toggle = ! toggle; //The toggle variable will change back and forth between "true" and "false" if(toggle){ //If the toggle variable is TRUE, then send 0xFF to the Arduino comPort.write(unhex(FFHex)); //The unhex() function converts the "FF" string to 0xFF background(0,0,255); //Change the background colour to blue as a visual indication of a button press. } else { comPort.write(unhex(zeroHex)); //If the toggle variable is FALSE, then send 0x00 to the Arduino background(0); //Change the background colour to black as a visual indication of a button press. } }
The Video
The tutorial above is a quick demonstration of how to convert Hex strings on your computer and send them to an Arduino. The Arduino can use the values to change the brightness of an LED as shown in this tutorial, however you could use it to modify the speed of a motor, or to pass on commands to another module. Hopefully this short tutorial will help you with your project. Please let me know how it helped you in the comments below.
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Building on the last project, I am now using a Red and a Yellow LED as a Sensor to detect light coming from an RGB LED.
Putting different coloured Mega Bloks over the LEDs has different effects on the Sensors as the RGB LED gets brighter and brighter.
I used the Processing Language to control the brightness of the RGB LED through a Serial command, and then use the resulting Sensor readings from the Yellow and the Red LEDs to create a chart or plot.
Here are the results of my experiment.
Red Mega Blok
Yellow Mega Blok
Green Mega Blok
When the displayed bars are RED, it indicates that the Red LED is absorbing MORE light than the Yellow LED (and vice versa). Hence this is a "Difference Chart". The Green Mega Blok absorbs more Red Light than the other blocks, therefore producing a big difference between Red LED sensor readings and Yellow Sensor readings.
Here is the list of components required to perform this experiment
//Define the pins for the Red LED Sensor #define Red_LED_Sensor_POS 4 #define Red_LED_Sensor_NEG 5
//Define the pins for the Yellow LED Sensor #define Yellow_LED_Sensor_POS 7 #define Yellow_LED_Sensor_NEG 8
//Define the pin for the RGB LED torch #define RGB_LED_RedPin 9 #define RGB_LED_GreenPin 10 #define RGB_LED_BluePin 11 int intensity=0;
//Define the maximum cycles/time allowed for each LED to capture light long max_darkness=80000;
voidsetup(){ //Setup the RED LED Sensor pinMode(Red_LED_Sensor_POS,OUTPUT); digitalWrite(Red_LED_Sensor_POS,LOW);
//Setup the YELLOW LED Sensor pinMode(Yellow_LED_Sensor_POS,OUTPUT); digitalWrite(Yellow_LED_Sensor_POS,LOW);
//No need to setup the RGB LED Pins
//Turn on Serial Protocol Serial.begin(9600); }
voidloop() {
byte byteRead; // check if data has been sent from the computer: if (Serial.available()) { // read the most recent byte (which will be from 0 to 255): byteRead = Serial.read(); // set the brightness of the LED: analogWrite(RGB_LED_RedPin, byteRead); analogWrite(RGB_LED_GreenPin, byteRead); analogWrite(RGB_LED_BluePin, byteRead);
//Read the amount of Yellow light read_LED('Y', Yellow_LED_Sensor_NEG);
//Read the amount of Red light read_LED('R', Red_LED_Sensor_NEG); } }
void read_LED(char LED_Colour, int LED_Pin){
// Charge the LED by applying voltage in the opposite direction pinMode(LED_Pin,OUTPUT); digitalWrite(LED_Pin,HIGH);
//Read the amount of Light coming into the LED sensor long darkness=0; int lightLevel=0; pinMode(LED_Pin,INPUT); digitalWrite(LED_Pin,LOW);
//This sketch was written by ScottC, but was adapted from a sketch //written by Tom Igoe in 2005
// This example code is in the public domain.
import processing.serial.*;
Serial myPort; // The serial port int xPos = 1; // horizontal position of the graph float YellowVal=0; // The variable to hold the Yellow Sensor Reading float RedVal=0; // The variable to hold the Red Sensor Reading float Diff=0; // The variable to hold the difference between the readings int Switcher=0; // Used to control the flow of the program
voidsetup () { // set the window size: size(1020, 750);
// List all the available serial ports println(Serial.list()); // I use COM13 for my Serial Port - you will need to change this to suit your system myPort = new Serial(this, "COM13", 9600); // don't generate a serialEvent() unless you get a newline character: myPort.bufferUntil('\\n'); // set inital background: background(0); //Send a value to the Arduino to start the feedback mechanism myPort.write(0); } voiddraw () { // everything happens in the serialEvent() }
void serialEvent (Serial myPort) { // get the ASCII string: String inString = myPort.readStringUntil('\\n');
if (inString != null) { // trim off any whitespace: inString = trim(inString);
//The arduino sends 2 sensor readings. The following code //helps to identify which reading is which. if(inString.equals("Y")){ Switcher=0; } elseif (inString.equals("R")){ Switcher=1; } else {
//Convert the String to a float float inByte = float(inString); //Map the reading, so that the chart fits within the window. inByte = map(inByte, 0, 1000, 0, height);
if(Switcher==0){ //Save the reading from the yellow sensor to YellowVal YellowVal=inByte; } else { //Save the reading from the red sensor to RedVal RedVal=inByte; //Calculate the difference between the readings Diff=RedVal-YellowVal;
//If the yellow sensor is greater, plot with a yellow line //If the red sensor reading is greater, plot a red line. if(Diff<=0){ stroke(255,255,0); Diff=abs(Diff); } else { stroke(255,0,0); } // draw the line: line(xPos, height, xPos, height - Diff);
// at the edge of the screen, go back to the beginning: if (xPos > width) { xPos = 0; background(0); //Send a value to the Arduino to change the intensity //of the RGB LED and take another reading myPort.write(xPos); } else { // increment the horizontal position: Increment by more // to get less readings and to make it quicker xPos+=4; if (xPos>0){ //Send a value to the Arduino to change the intensity //of the RGB LED and take another reading myPort.write(xPos/4); } else { myPort.write(xPos); } } } } } }
