Arduino tutorial 15a – RFID with Innovations ID-20

Learn how to use RFID readers with your Arduino. In this instalment we use the Innovations ID-20 RFID reader. The ID-12 and ID-2 are also compatible. If you have the RDM630 or RDM6300 RFID reader, we have a different tutorial.

This is part of a series originally titled “Getting Started with Arduino!” by John Boxall – A tutorial on the Arduino universe. The first chapter is here, the complete series is detailed here.

Updated 26/02/2013

RFID – radio frequency identification. Some of us have already used these things, and they have become part of everyday life. For example, with electronic vehicle tolling, door access control, public transport fare systems and so on. It sounds complex – but isn’t. In this tutorial we’ll run through the basics of using the ID-20 module then demonstrate a project you can build and expand upon yourself.

Introduction

To explain RFID for the layperson, we can use a key and lock analogy. Instead of the key having a unique pattern, RFID keys hold a series of unique numbers which are read by the lock. It is up to our software (sketch) to determine what happens when the number is read by the lock.  The key is the tag, card or other small device we carry around or have in our vehicles. We will be using a passive key, which is an integrated circuit and a small aerial. This uses power from a magnetic field associated with the lock. Here are some key or tag examples:

In this tutorial we’ll be using 125 kHz tags – for example. To continue with the analogy our lock is a small circuit board and a loop aerial. This has the capability to read the data on the IC of our key, and some locks can even write data to keys. And out reader is the Innovations ID-20 RFID reader:

Unlike the RDM630 reader in the other RFID tutorial – the ID-20 is a complete unit with an internal aerial and has much larger reader range of around 160 mm. It’s a 5V device and draws around 65 mA of current. If you have an ID-12 it’s the same except the reader range is around 120mm; and the ID-2 doesn’t have an internal aerial. Connecting your ID-20 reader to the Arduino board may present a small challenge and require a bit of forward planning. The pins on the back of the reader are spaced closer together than expected:

… so a breakout board makes life easier:

… and for demonstration and prototyping purposes, we’ve soldered on the breakout board with some header pins:

 The first thing we’ll do is connect the ID-20 and demonstrate reading RFID tags. First, wire up the hardware as shown below:

If you’re using the breakout board shown earlier, pin 7 matches “+/-” in the diagram above. Next, enter and upload the following sketch (download):

// Example 15a.1

#include <SoftwareSerial.h>
SoftwareSerial id20(3,2); // virtual serial port
char i;
void setup() 
{
 Serial.begin(9600);
 id20.begin(9600);
}

void loop () 
{
 if(id20.available()) {
 i = id20.read(); // receive character from ID20
 Serial.print(i); // send character to serial monitor
 Serial.print(" ");
 }
}

Note that we’re using a software serial port for our examples. In doing so it leaves the Arduino’s serial lines for uploading sketches and the serial monitor. Now open the serial monitor window, check the speed is set to 9600 bps and wave some tags over the reader – the output will be displayed as below (but with different tag numbers!):

Each tag’s number starts with a byte we don’t need, then twelve that we do, then three we don’t. The last three aren’t printable in the serial monitor. However you do want the twelve characters that appear in the serial monitor.  While running this sketch, experiment with the tags and the reader… get an idea for how far away you can read the tags. Did you notice the tag is only read once – even if you leave it near the reader? The ID-20 has more “intelligence” than the RDM630 we used previously. Furthermore when a tag is read, the ID-20 sends a short PWM signal from pin 10 which is  just under 5V and lasts for around 230 ms, for example (click image to enlarge):

 This signal can drive a piezo buzzer or an LED (with suitable resistor). Adding a buzzer or LED would give a good notification to the user that a card has been read. While you’re reading tags for fun, make a note of the tag numbers for your tags – you’ll need them for the next examples.

RFID Access System

Now that we can read the cards, let’s create a simple control system. It will read a tag, and if it’s in the list of allowed tags the system will do something (light a green LED for a moment). Plus we have another LED which stays on unless an allowed tag is read.  Wire up the hardware as shown below (LED1 is red, LED2 is green – click image to enlarge):

Now enter and upload the following sketch (download):

// Example 15a.2

#include 
SoftwareSerial id20(3,2); // virtual serial port

// add your tags here. Don't forget to add to decision tree in readTag();
String Sinclair = "4F0023E2129C";
String Smythe = "4F0023CC9737";
String Stephen = "010044523C2B";

String testcard; 
char testtag[12]; 
int indexnumber = 0; 
char tagChar;

void setup() 
{
 Serial.begin(9600);
 pinMode(7, OUTPUT); // this if for "rejected" red LED
 pinMode(9, OUTPUT); // this will be set high when correct tag is read. Use to switch something on, for now - a green LED. 
 id20.begin(9600); 
 digitalWrite(7, LOW);
 digitalWrite(9, LOW);
}

void approved()
// when an approved card is read
{
 digitalWrite(9, HIGH);
 Serial.println("yes"); 
 delay(1000);
 digitalWrite(9, LOW);
}

void notApproved()
// when an unlisted card is read
{
 digitalWrite(7, HIGH);
 Serial.println("no");
 delay(100);
 digitalWrite(7, LOW);
}

void readTag()
{
 tagChar = id20.read();
 if (indexnumber != 0) // never a zero in tag number
 {
 testtag[indexnumber - 1] = tagChar;
 }
 indexnumber++;
 if (indexnumber == 13 ) // end of tag number
 {
 indexnumber = 0;
 testcard = String(testtag);
 if (testcard.equals(Sinclair)) { 
 approved(); 
 } 
 else if (testcard.equals(Smythe)) { 
 approved(); 
 }
 else if (testcard.equals(Stephen)) { 
 approved(); 
 }
 else { 
 notApproved(); 
 }
 }
}

void loop()
{
 readTag();
}

In the function readCard() the sketch reads the tag data from the ID-20, and stores it in an array testtag[]. The index is -1 so the first unwanted tag number isn’t stored in the array. Once thirteen numbers have come through (the one we don’t want plus the twelve we do want) the numbers are smooshed together into a string variable testcard with the function String. Now the testcard string (the tag just read) can be compared against the three pre-stored tags (Sinclair, Smythe and Stephen).

Then it’s simple if… then… else to to see if we have a match, and if so – call the function approved() or disApproved as the case may be. In those two functions you store the actions you want to occur when the correct card is read (for example, control a door strike or let a cookie jar open) or when the system is waiting for another card/a match can’t be found. If you’re curious to see it work, check the following video where we take it for a test run and also show the distances that you have to work with:

Hopefully this short tutorial was of interest. We haven’t explored every minute detail of the reader – but you now have the framework to move forward with your own projects.

Have fun and keep checking into tronixstuff.com. Why not follow things on twitter, Google+, subscribe  for email updates or RSS using the links on the right-hand column, or join our Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

Tutorial: Arduino and Infra-red control

Learn how to use Arduino and infra-red remote controls in chapter thirty-two of a series originally titled “Getting Started/Moving Forward with Arduino!” by John Boxall – A tutorial on the Arduino universe. The first chapter is here, the complete series is detailed here.

Updated 05/02/2013

In this article we will look at something different to the usual, and hopefully very interesting and useful – interfacing our Arduino systems with infra-red receivers. Why would we want to do this? To have another method to control our Ardiuno-based systems, using simple infra-red remote controls.

A goal of this article is to make things as easy as possible, so we will not look into the base detail of how things work - instead we will examine how to get things done. If you would like a full explanation of infra-red, perhaps see the page on Wikipedia. The remote controls you use for televisions and so on transmit infra-red beam which is turned on and off at a very high speed – usually 38 kHz, to create bits of serial data which are then interpreted by the receiving unit. As the wavelength of infra-red light is too high for human eyes, we cannot see it. However using a digital camera – we can. Here is a demonstration video of IR codes being sent via a particularly fun kit – the adafruit TV-B-Gone:

Now to get started. You will need a remote control, and a matching IR receiver device. The hardware and library used in this tutorial only  supports NEC, Sony SIRC, Philips RC5, Philips RC6, and raw IR protocols. Or you can purchase a matching set for a good price, such as this example:

Or you may already have a spare remote laying around somewhere. I kept this example from my old Sony Trinitron CRT TV after it passed away:

It will more than suffice for a test remote. Now for a receiver – if you have purchased the remote/receiver set, you have a nice unit that is ready to be wired into your Arduino, and also a great remote that is compact and easy to carry about. To connect your receiver module – as per the PCB labels, connect Vcc to Arduino 5V, GND to Arduino GND, and D (the data line) to Arduino digital pin 11.

Our examples use pin 11, however you can alter that later on. If you are using your own remote control, you will just need a receiver module. These are very cheap, and an ideal unit is the Vishay TSOP4138 (data sheet .pdf). These are available from element-14 and the other usual retail suspects. They are also dead-simple to use. Looking at the following example:

From left to right the pins are data, GND and Vcc (to Arduino +5V). So it can be easily wired into a small breadboard for testing purposes. Once you have your remote and receiver module connected, you need to take care of the software side of things. There is a new library to download and install, download it from here. Extract the IRremote folder and place into the ..\arduino-002x\libraries folder. Then restart your Arduino IDE if it was already open.

Using Arduino v1.0? Open the file “IRRemoteInt.h” in the library folder, and change the line

#include <WProgram.h>

to

#include <Arduino.h>

Then save and close the file, restart the Arduino IDE and you’re set.

Example 32.1

With our first example, we will receive the commands from our remote control and display them on the serial monitor. Download and run the following sketch:

// example 32.1 - IR receiver code repeater

// http://tronixstuff.com/tutorials > chapter 32

// based on code by Ken Shirriff - http://arcfn.com

#include <IRremote.h> // use the library

int receiver = 11; // pin 1 of IR receiver to Arduino digital pin 11

IRrecv irrecv(receiver); // create instance of 'irrecv'

decode_results results;

void setup()

{

  Serial.begin(9600); // for serial monitor output

  irrecv.enableIRIn(); // Start the receiver

}

void loop()

{

  if (irrecv.decode(&results)) // have we received an IR signal?

  {

    Serial.println(results.value, HEX); // display it on serial monitor in hexadecimal

    irrecv.resume(); // receive the next value

  }  // Your loop can do other things while waiting for an IR command

}

Open the serial monitor box, point your remote control to the receiver and start pressing away. You should see something like this:

What have we here? Lots of hexadecimal numbers. Did you notice that each button on your remote control resulted in an individual hexadecimal number? I hope so. The number FFFFFFFF means that the button was held down. The remote used was from a yum-cha discount TV. Now I will try again with the Sony remote:

This time, each button press resulted in the same code three times. This is peculiar to Sony IR systems. However nothing to worry about. Looking back at the sketch for example 32.1, the

if (irrecv.decode(&results))

section is critical – if a code has been received, the code within the if statement is executed. The hexadecimal code is stored in the variable

results.value

with which we can treat as any normal hexadecimal number. At this point, press a few buttons on your remote control, and take a note of the matching hexadecimal codes that relate to each button. We will need these codes for the next example…

Example 32.2

Now we know how to convert the infra-red magic into numbers, we can create sketches to have our Arduino act on particular commands. As the IR library returns hexadecimal numbers, we can use simple decision functions to take action. In the following example, we use switch…case to examine each inbound code, then execute a function. In this case we have an LCD module connected via I2C, and the sketch is programmed to understand fifteen Sony IR codes. If you don’t have an LCD you could always send the output to the serial monitor. If you are using the DFRobot I2C LCD display, you need to use Arduino v23.

Furthermore you can substitute your own values if not using Sony remote controls. Finally, this sketch has a short loop after the translateIR(); function call which ignores the following two codes – we do this as Sony remotes send the same code three times. Again. you can remove this if necessary. Note that when using hexadecimal numbers in our sketch we preced them with 0x.

Download the sketch below from here:

// example 32.2 - IR receiver code translator

// for Sony IR codes (ignores 2nd and 3rd signal repeat)

// http://tronixstuff.com/tutorials > chapter 32

// based on code by Ken Shirriff - http://arcfn.com

#include "Wire.h" // for I2C bus

#include "LiquidCrystal_I2C.h" // for I2C bus LCD module http://bit.ly/eNf7jM

LiquidCrystal_I2C lcd(0x27,16,2);  // set the LCD address to 0x27 for a 16 chars and 2 line display

#include <IRremote.h> // use the library for IR

int receiver = 11; // pin 1 of IR receiver to Arduino digital pin 11

IRrecv irrecv(receiver); // create instance of 'irrecv'

decode_results results;

void setup()

{

  lcd.init();          // initialize the lcd

  lcd.backlight(); // turn on LCD backlight

  irrecv.enableIRIn(); // Start the receiver

}

void translateIR() // takes action based on IR code received

// describing Sony IR codes on LCD module

{

  switch(results.value)

  {

    case 0x37EE: lcd.println(" Favourite      "); break;

    case 0xA90: lcd.println(" Power button   "); break;

    case 0x290: lcd.println(" mute           "); break;

    case 0x10:  lcd.println(" one            "); break;

    case 0x810:  lcd.println("  two           "); break;

    case 0x410:  lcd.println(" three          "); break;

    case 0xC10:  lcd.println(" four           "); break;

    case 0x210:  lcd.println(" five           "); break;

    case 0xA10:  lcd.println(" six            "); break;

    case 0x610:  lcd.println(" seven          "); break;

    case 0xE10:  lcd.println(" eight          "); break;

    case 0x110:  lcd.println(" nine           "); break;

    case 0x910:  lcd.println(" zero           "); break;

    case 0x490:  lcd.println(" volume up      "); break;

    case 0xC90:  lcd.println(" volume down    "); break;

    case 0x90:   lcd.println(" channel up     "); break;

    case 0x890:  lcd.println(" channel down   "); break;

    default: lcd.println(" other button   ");

  }

  delay(500);

  lcd.clear();

}

void loop()

{

  if (irrecv.decode(&results)) // have we received an IR signal?

  {

    translateIR();

    for (int z=0; z<2; z++) // ignore 2nd and 3rd signal repeat

    {

      irrecv.resume(); // receive the next value

    }

  }

}

And here it is in action:

You might be thinking “why would I want to make things appear on the LCD like that?”. The purpose of the example is to show how to react to various IR commands. You can replace the LCD display functions with other functions of your choosing.

At the start working with infra-red may have seemed to be complex, but with the previous two examples it should be quite simple by now. So there you have it, another useful way to control our Arduino systems. Hopefully you have some ideas on how to make use of this technology. In future articles we will examine creating and sending IR codes from our Arduino. So stay tuned for upcoming Arduino tutorials by subscribing to the blog, RSS feed (top-right), twitter or joining our Google Group. Furthermore, a big thanks to Ken Shirriff for his Arduino library.

Have fun and keep checking into tronixstuff.com. Why not follow things on twitter, Google+, subscribe  for email updates or RSS using the links on the right-hand column, or join our Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

The DFRobot LCD4884 LCD Shield

Learn how to use the DFRobot LCD4884 Arduino LCD shield.

Updated 19/03/2013

This needs to be updated for use with Arduino IDE v1.0.1 and greater… however I can’t locate my shield to test it. Stay tuned via twitter to find out when this is updated.

This article is my response to a request on how to use the LCD4884 LCD shield from DFRobot in China. It is a simple way of displaying text and the odd graphic, as well as another way to accept user input. Here is the shield in question:

From a hardware perspective the LCD has a resolution of 84 by 48 pixels, with a blue back light. It can easily display six rows of fourteen alphanumeric characters, or two rows of six very large characters. Furthermore, it can display bitmap images that are appropriately sized. At the top-left of the shield digital pins eight to thirteen have been expanded with matching Vcc and GND pins, and at the bottom right the same has been done with analogue pins one through to five. Therefore if using this shield, you will lose digital pins two through to seven and analogue zero.

Along the bottom-left of the shield are solder pads for some other I/O options, however I couldn’t find any documentation on how these are used. Below the LCD is a small four-way joystick that also has an integral button. This is connected to analog pin zero via a resistor network. This joystick can be used for user input and also to create some nifty menu systems. To the right is a power-on LED which is really too bright, I would recommend sanding it a little to reduce the intensity, or just melting it off with a soldering iron.

The shield requires an Arduino library which can be downloaded from the shield’s wiki page. There is also a good demonstration sketch on the wiki, however some of our readers may find this to be somewhat complex. Therefore where possible I will break down and explain the functions in order to simplify use of the shield, then use them in a demonstration sketch.

Controlling the backlight is very easy, just use digitalWrite(7, HIGH/LOW) to turn it on and off. Don’t forget to put pinMode(7, OUTPUT) in void setup();.

Reading the joystick position is accomplished via analogRead(0);. It returns the following values as such:

• Up – 505
• Down – 0
• Left – 740
• Right – 330
• pressed in – 144
• Idle (no action) – 1023

By using analogRead(0) and if… statements you can read the joystick in a simple way. Don’t forget to allow for some tolerance in the readings. Attempts to press the button while forcing a direction did not return any different values. In the example sketch later on, you can see how this is implemented. Always remember to insert:

lcd.LCD_init();

in void setup() to create an instance of the LCD, and

#include <LCD4884.h>

at the start of your sketch to enable the library.

Now to display text on the LCD. Here is an example of the standard font text:

Using the standard font, we can position text using the following function:

lcd.LCD_write_string(x,y,"insert text here", MENU_NORMAL); // ignore MENU_NORMAL for now

The parameter x is for the x-coordinate of the first character – measured in pixels, not characters. However y is the coordinate in character lines (!). The screen can display six lines of fourteen characters. To display the larger font, for example:

use the following:

lcd.LCD_write_string_big(x,y, "012345", MENU_NORMAL);

Unfortunately the library only supports the digits 0~9, +, – and decimal point. You can modify the file font_big.h in the library folder and create your own characters. Once again the x parameter is the number of pixels across to place the first character, and y is 0 for the top line and 3 for the bottom line. Notice that the characters in this font are proportional, however the maximum number of digits to plan for in one line would be six.

To clear the display, use:

lcd.LCD_clear();

By now you will be able to display text, control the backlight and read the joystick. The following demonstration sketch (download) puts it all together so far:

#include <LCD4884.h>

int z=0;

int dd=200;

void setup()

{

lcd.LCD_init(); // creates instance of LCD

lcd.LCD_clear(); // blanks the display

pinMode(7, OUTPUT);

}

void loop()

{  // first some text display

for (int a=0; a<5; a++)

{

digitalWrite(7, LOW);

delay(300);

digitalWrite(7, HIGH);

delay(300);

}

for (int a=0; a<6; a++)

{

lcd.LCD_write_string(0,a,"01234567980123", MENU_NORMAL); // ignore MENU_NORMAL for now

delay(dd);

}

delay(dd);

lcd.LCD_clear();   // blanks the display

delay(500);

lcd.LCD_write_string_big(0, 0, "012345", MENU_NORMAL);

lcd.LCD_write_string_big(0, 3, "-+-+-+", MENU_NORMAL);

delay(1000);

lcd.LCD_clear();  // now to read the joystick using analogRead(0). Press RESET whien finished

do

{

z=analogRead(0);

if (z==0)

{

lcd.LCD_write_string(2,2,"Down", MENU_NORMAL);

}     else

if (z>0 && z<150)

{

lcd.LCD_write_string(2,2,"OK   ", MENU_NORMAL);

delay(dd);

}       else

if (z>150 && z<350)

{

lcd.LCD_write_string(2,2,"Right", MENU_NORMAL);

delay(dd);

}         else

if (z>350 && z<510)

{

lcd.LCD_write_string(2,2,"Up   ", MENU_NORMAL);

delay(dd);

}         else

if (z>510 && z<750)

{

lcd.LCD_write_string(2,2,"Left ", MENU_NORMAL);

delay(dd);

}           else

if (z>750)

{

lcd.LCD_write_string(2,2,"nil  ", MENU_NORMAL);

delay(dd);

}

}  while (1>0);

}

Next is to create and display bitmap images. Images can be up to 84 x 48 pixels in size. There are no shades of grey in the images, just pixels on or off. To display a bitmap is a convoluted process but can be mastered. We need to convert a bitmap image into hexadecimal numbers which are then stored in a text file for inclusion into the sketch. To do so, follow these steps:

Create your monochrome image using an editor such as Gimp. Make sure your file name ends with .bmp. Such as:

Next, download the BMP2ASM program from this website. [Sorry, could only find a Windows version]. Open your .bmp file as created above, and you will see a whole bunch of hexadecimal numbers at the bottom of the window:

Turn on the check boxes labelled “Stretch”, “Use Prefix” and “Use suffix”. Then click “Convert”. Have a look in your folder and you will find a text file with an extension .asm. Open this file in a text editor such as Notepad. Remove all the instances of “dt”, as well as the top line with the file path and name. Finally, put commas at the end of each line.

You should now be left with a file of hexadecimal numbers. Encase these numbers in the form of an array as such:

What we have done is places the hexadecimal numbers inside the

unsigned char hellobmp[]= {}

declaration. To make life simpler, ensure the filename (ending with .h) is the same as the variable name, as in this example it is called hellobmp(.h). And make sure you have saved this file in the same folder as the sketch that will use it.

Finally, we include the hellobmp.h file in our example sketch to display the image:

#include "LCD4884.h"

#include "hellobmp.h" // this file needs to be in the same folder as your sketch

void setup()

{

  lcd.LCD_init(); // creates instance of LCD

  lcd.LCD_clear(); // blanks the display

}

void loop()

{

   lcd.LCD_draw_bmp_pixel(0,0, hellobmp, 84,48);

   do { } while (1>0); // do nothing

}

Notice in the function lcd.LCD_draw_bmp_pixel the filename hellobmp is the same as in the #include declaration is the same as the hellobmp.h file we created. They all need to match. Furthermore, the four numerical parameters are the bitmap’s top-left x-y and bottom-right x-y coordinates on the LCD. So after all that, here is the result:

So there you have it. If you have any questions about this LCD shield contact DF Studio, or ask a question in our Google Group.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitter, Google+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

Project – Simple RFID access system

In this tutorial you can make an RFID access system. It’s very simple and can be used with a wide variety of end-uses.

Updated 18/03/2013

The purpose of this project is to prototype a basic RFID access system. Although it is not that complicated, this article is my response to a kit reviewed in the Australian “Silicon Chip” (November 2010) electronics magazine. Their article describes the kit in detail – operation, schematic, use and installation. However the code for the microcontroller (PIC16F628A)  is not published due to the kit manufacturer holding copyright over the design. This is a shame, as many organisations have been quite successful selling open-source kits. So instead of moaning about it, I have created my own design that matches the operation of the original, instead using the ATmega328 MCU with Arduino bootloader. Consider this a basic framework that you can modify for your own access system, or the start of something more involved.

original article

There are pros and cons with the original vs. my version. The biggest pro is that you can buy the whole kit for around Au$40 including a nice PCB, solder it together, and it works. However if you want to do it yourself, you can modify it to no end, and have some fun learning and experimenting along the way. So let’s go!

The feature requirements are few. The system must be able to learn and remember up to eight RFID access tags/cards, etc – which must be able to be altered by a non-technical user. Upon reading a card, the system will activate a relay for a period of time (say 1 second) to allow operation of a door strike or electric lock. Finally, the RFID tag serial numbers are to be stored in an EEPROM in case of a power outage. When a tag is read, a matching LED (1~8) will show which tag was read. There are also two LEDs, called “Go” and “Stop” which show the activation status. The original kit has some more LEDs, which I have made superfluous by blinking existing LEDs.

This is a simple thing to make, and the transition from a solderless breadboard to strip board will be easy for those who decide to make a permanent example. But for now, you can follow with the prototype. First is the parts list:

• Atmel ATmega328 with Arduino bootloader;
• 16 MHz resonator (X1 in schematic);
• ten LEDs of your choice;
• two normally-open push buttons;
• two 560 ohm resistors (all resistors 1/4 watt);
• one 1k ohm resistor;
• three 10k ohm resistors;
• one BC548 transistor;
• three 0.01 uF monolithic capacitors;
• one 100 uF electrolytic capacitor;
• one 1N4004 diode;
• Microchip 24LC256 EEPROM;
• 125 kHZ RFID module;
• 125 kHz RFID tags/cards;
• connecting wire;
• large solderless breadboard;
• LM7805 power regulator;
• relay of your choice with 5V coil (example).

When selecting a relay, make sure it can handle the required load current and voltage – and that the coil current is less than 100mA.

If attempting to switch mains voltage/current – contact a licensed electrician. Your life is worth more than the money saved by not consulting an expert.

And here is the schematic:

Here is the prototype on the solderless breadboard. For demonstration purposes an LED has been substituted for the transistor/relay section of the circuit, the power regulator circuitry has not been shown, and there are superfluous 4.7k resistors on the I2C bus. To program the software (Arduino sketch) the easiest way is by inserting the target IC into an Arduino-compatible board, or via a 5V FTDI cable and a basic circuit as described here.

The Arduino sketch is also quite simple. The main loop calls the procedure readTags() to process any RFID tag read attempts, and then monitors button A – if pressed, the function learnTags() is called to allow memorisation of new RFID tags. Each tag serial number consists of 14 decimal numbers, and these are stored in the EEPROM sequentially. That is, the first tag’s serial number occupies memory positions 0~13, the second tag’s serial number occupies memory position 14~28, and so on. Two functions are used to read and write tag serial numbers to the EEPROM – readEEPROMtag() and writeEEPROMtag(). The EEPROM is controlled via the I2C bus. For a tutorial about Arduino, I2C bus and the EEPROM please read this article. For a tutorial about Arduino and RFID, please read this article. The rest of the sketch is pretty self-explanatory. Just follow it along and you can see how it works. You can download the sketch from here.

 
And finally, a quick video demonstration:

So there you have it. I hope you enjoyed reading about this small project and perhaps gained some use for it of your own or sparked some other ideas in your imagination that you can turn into reality.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitter, Google+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

Moving Forward with Arduino – Chapter 19 – GPS part II

This is part of a series originally titled “Getting Started with Arduino!” by John Boxall – A tutorial on the Arduino universe. The first chapter is here, the complete series is detailed here.

Updated 24/01/2013

In this instalment we will continue to examine the use of our GPS system and Arduino through creating two more applications. Some of them may seem simple, but we will build on them later on to make more complex things. To review previous information, the first GPS instalment was chapter seventeen.

Example 19.1 – “Household official time”

At home we often have various discussions about what the actual time is. At first it sounds silly, but when you have clocks on the microwave, kitchen wall, a wristwatch, mobile phone, clock-radio, and so on – things can get a little out of hand. And my better half has all her clocks ten minutes fast. Insanity may prevail!

So let’s make a nice big LED-display reference clock – something that wouldn’t look out of place in a radio or television studio:

Then when people start arguing over the time, you can point at your new clock and smile. From a hardware perspective, we will combine three or four things: our Arduino board, our GPS system, and the MAX7219 display driver. We will need the following items:

• Arduino Uno or compatible board
• the GPS shield bundle
• Maxim MAX7219 display driver IC
• two four-digit, seven-segment LED displays (common cathode). You could also rig up four separate digits with some patience;
• one 1 kilo ohm resistor
• one 10 kilo ohm resistor
• one single pole, double-throw switch
• a nice breadboard and some connecting wire
• a separate 5V power supply – all those LED segments are thirsty, the completed clock uses under 350 milliamps with a brightness setting of 8:

Here is the schematic:

Although the sketch (download) may seem quite complex, it is just made up of things we have already examined in the past. The only unfamiliar part could be the MAX7219 display driver IC, which in itself is quite easy to use. There is a full part review and explanation here. It is most likely that everyone will have different LED display units, as the 4-digit modules can be hard to track for some people or too expensive –  so some more explanation is in order.

You will need common-cathode display modules. If you line the digits up from left to right, they will be numbered zero to nine with respect to the MAX7219 – so connect MAX7219 pin 2 to the cathode of your first display, and so on. With regards to the anodes (a~g and dp [decimal point]) – link each anode type together.

For example, if you have eight separate 7-segment display modules, connect each ‘a’ pin together, then to MAX pin 14. And so on. Here is the board layout – a real mess:

And our action video:

An interesting twist you might find of interest is the function:

lc.setIntensity(0,8);

Which allows you to alter the brightness of the LED display(s). The range is 0 to 18 – in my examples it has been set to 8. You could then make your clock dim the display brightness between (for example) 11pm and 5am – so when you wake up in the middle of the night the display won’t act like a frickin’  laser-beam burning into your eyeballs. Furthermore, dropping the brightness reduces the power consumption.

Example 19.2 – “You went… where?”

Now it is time for what most of you have been waiting for – making a GPS tracking device. Now before you get too excited, it would be proper to make sure you have the permission of someone before you track them. From a hardware perspective this example is a lot easier that you think – it is just the Arduino board, GPS shield and microSD shield. You will need to install TinyGPS library if not already installed.

Then, we will need the following items:

• Arduino Uno or compatible board
• the GPS shield bundle
• microSD shield and a matching memory card up to 2GB in size
• portable power, for example an alkaline 9V PP3 battery and adaptor cable

Download the Example 19.2 sketch from here.

Don’t forget to format the microSD card to FAT16 before use. Once power is applied, the system will take a position reading and write it to the microSD card every 30 seconds. You can alter this period by changing the value in the delay() function at the end of  void getgps(TinyGPS &gps). The text file is closed after every write, so you can just turn it off when finished then take the memory card to the computer to copy the data.

Although the hardware wasn’t that interesting to plug together, what can be done with it and the data it captures is quite fascinating. To generate some sample data, I have taken the hardware for a walk to the post office. We will now open the file produced by our hardware and examine it further. If you would like to follow along, you can download the file from here.

The file is a typical, comma-delimited text file. You can examine it further using common spreadsheet software such as LibreOffice Calc. For example, if you open the file of GPS data from here, you will be presented with the following window:

You can see that the data delimits quite easily. Just click “OK” and the file will be presented to you.

So as you can see, there is time, date (remember – GMT), latitude and longitude, my speed (with a couple of anomalies) and random sensor data results (see the sketch). We can have this data converted into a much more useful form by using the GPS Visualiser website. Save the data as a .csv file. Then visit http://www.gpsvisualizer.com/, and use the Get Started Now box in the middle of the web page. Select Google Maps as the output format, then upload the file. This will result in the following:

Just like normal Google Maps there are many display options you can choose from, and the GPS Visualiser web site has many tutorials about making the most of their service. If you look in detail you will see some “jittering” along parts of the track that are not representative of my movements (though I had just taken my morning coffee). This could be the result of the receiver module moving about in all three axes during my walk, one would imagine it would be a lot smoother inside a motor vehicle. So have fun with that.

Have fun and keep checking into tronixstuff.com. Why not follow things on twitter, Google+, subscribe  for email updates or RSS using the links on the right-hand column, or join our Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

Moving Forward with Arduino – Chapter 17 – GPS

This is part of a series originally titled “Getting Started with Arduino!” by John Boxall – A tutorial on the Arduino universe. The first chapter is here, the complete series is detailed here.

Updated 23/01/2013

In this instalment we will introduce and examine the use of the Global Positioning System receivers with Arduino systems. What is the GPS? In very simple terms, a fleet of satellites orbit the earth, transmitting signals from space. Your GPS receiver uses signals from these satellites to triangulate position, altitude, compass headings, etc.; and also receives a time and date signal from these satellites. The most popular GPS belongs to the USA, and was originally for military use – however it is now available for users in the free world.

Interestingly, the US can switch off or reduce accuracy of their GPS in various regions if necessary, however many people tell me this is not an issue unless you’re in a combat zone against the US forces. For more information, have a look at Wikipedia or the USAF Space Command GPS Ops Centre site. As expected,  other countries have their own GPS as well – such as Russia, China, and the EU is working on one as well.

So – how can us mere mortals take advantage of a multi-billion dollar space navigation system just with our simple Arduino? Easy – with an inexpensive GPS receiver and shield. When searching for some hardware to use, I took the easy way out and ordered this retail GPS pack which includes the required Arduino shield and header sockets, short connecting cable and an EM-406A 20-channel GPS receiver with in-built antenna:

For reference now and in the future, here is the data book for the GPS receiver: EM-406 manual.pdf. All you will need is an Arduino Uno or 100% compatible board, and the usual odds and ends. When it comes time to solder up your shield, if possible try and sit it into another shield or board – this keeps the pins in line and saves a lot of trouble later on:

And we’re done:

Please notice in the photo above the cable is a lot longer between the shield and the GPS receiver. This was an extra cable, which makes things a lot more convenient, and it never hurts to have a spare. Finally, on the shield please take note of the following  two switches – the shield/GPS power switch:

and the UART/DLINE switch:

For now, leave this set to UART while a sketch is running. When uploading a sketch to the board, this needs to be on DLINE. Always turn off your GPS shield board before changing  this switch to avoid damage. Example 17.1 – Is anyone out there? Now, let’s get some of that juicy GPS data from outer space. You will need:

• Arduino Uno or compatible board
• a suitable GPS setup – for example the GPS shield bundle

Once you have your hardware assembled, upload the following sketch. Now for desk jockeys such as myself, there is a catch – as a GPS receives signals from satellites the receiver will need to be in line of sight with the open sky. If you have your desk next to a window, or a portable computer you’re in luck.  Look at the LED on your GPS receiver – if it is blinking, it has a lock (this is what you want); on - it is searching for satellites; off - it is off (!). The first time you power up your receiver, it may take a  minute or so to lock onto the available satellites, this period of time is the cold start time.

This will be in ideal conditions – i.e. with a clear line of sight from the unit to the sky (clouds excepted!). Once this has been done, the next time you power it up, the searching time is reduced somewhat as our receiver stores some energy in a supercap (very high-value capacitor) to remember the satellite data, which it will use the next time to reduce the search time (as it already has a “fair idea” where the satellites are). Now open the serial monitor box, sit back and wait a moment or two, and you should be presented with something very similar to this:

What a mess. What on earth does all that mean? For one thing the hardware is working correctly. Excellent! Now how do we decode these space-signals… They are called NMEA codes. Let’s break down one and see what it means. For example, the line: $GPRMC,165307.000,A,2728.9620,S,15259.5159,E,0.20,48.84,140910,,*27 Each field represents:

• $GPRMC tells us the following data is essential point-velocity-time data;
• 165307.000 is the universal time constant (Greenwich Mean Time) – 16:53:07 (hours, minutes, seconds). So you now have a clock as well.
• A is status – A for active and data is valid, V for void and data is not valid.
• 2728.9620 is degrees latitude position data = 27 degrees, 28.962′
• S for south (south is negative, north is positive)
• 15259.5159 is degrees longitude position data = 152 degrees, 59.5159′
• E for east (east is positive, west is negative)
• 0.20 is my speed in knots over ground. This shows the inaccuracy  that can be caused by not having a clear view of the sky
• 48.84 – course over ground (0 is north, 180 is south, 270 is west, 90 is east)
• 140910 is the date – 14th September, 2010
• the next is magnetic variation for which we don’t have a value
• checksum number

Thankfully the data is separated by commas. This will be useful if you are logging the data to a text file using a microSD shield, you will then be able to use the data in a spreadsheet very easily. Later on we will work with data from other codes, but if you can’t wait, here is the NMEA Reference Manual that explains them all. In the meanwhile, how can we convert the location data (longitude and latitude) received into a position on a map?

• Visit this website
• In the box that says “paste your data here”, enter (for example, using my data above)

name,desc,latitude,longitude home,home,-2728.9660,15259.5143

For example: Then click “Draw the Map”, and you will be presented with a Google map in a new window that you can zoom around in, change views and so on. Interestingly enough the coordinates returned in the test above were accurate down to around three meters. Later on that website will be of great use, as you can import text files of coordinates, and it will plot them out for you. If you use this mapping site a lot, please consider making a donation to help them out. Now as always, there is an easier way. The purpose of the previous demonstrations were to see the raw data that comes from a receiver, and understand how to work with it.

Moving on… now we can receive GPS signals – and in the past we have used LCD modules – so we can make our own variations of portable (!) GPS modules and other devices. At this point you will need to install another Arduino library - TinyGPS. So download and install that before moving forward.

Example 17.2 – My First GPS

Using various pieces of hardware from the past, we will build a simple, portable unit to display our data.

You will need:

• Arduino Uno or compatible board
• a suitable GPS setup – for example the GPS shield bundle;
• An LCD with HD44780 interface that has the ability to connect to your Arduino system. The size is up to you, we’re using a 20 x 4 character unit. If you have dropped in or are a bit rusty on LCDs, please read chapter twenty-four;
• An external power supply for your setup (if you want to walk up and down the street at midnight like I did) – for example, a 9V battery snap soldered to a DC plug is a quick and dirty solution!

Luckily I have made an LCD shield in the past which works nicely, and doesn’t use digital pins D0 and D1 – these are used by the GPS shield to get the data back to the Arduino. Therefore the whole lot just plugged in together as shields do. Here is the sketch for your consideration. Before uploading the sketch, turn off the GPS shield, set the DLINE/UART switch on the GPS shield to DLINE, upload the sketch, then set it back again, then back on with the GPS shield.

So here it is all thrown together in my lunch box:

And a close-up view of the LCD. There was not room for the course data, but you can modify the sketch accordingly. The data will be a little off due to the photo being taken indoors:

Now for some outdoor fun. In the video clip below, we take a ride on the bus and see our GPS in action…

I had to take an old bus that wasn’t full of security cameras, so the ride is bumpy:

As we have a lot of electronics in this setup, it would be interesting to know the current draw – to help plan for an appropriate power supply. The trusty meter gives us:

Wow – a maximum of 122 milliamps even with that LCD backlight blazing away. So when we make some GPS logging devices without such a monstrous LCD, we should be able to get the current draw down a lot more.

The purpose of this example was to show how you can manipulate the data from the GPS receiver. We continue with GPS part II here.

Have fun and keep checking into tronixstuff.com. Why not follow things on twitter, Google+, subscribe  for email updates or RSS using the links on the right-hand column, or join our Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.