Among the RFID modules, Stronglink SL018 is the lowest cost RFID module that I can get which supports read and write. SL018 is a 13.56MHz RFID module, it supports Mifare 1K, Mifare 4K and Mifare Ultralight. The specification are as follow:

Model	MIFARE Module SL018
Frequency	13.56MHz
Protocol	ISO14443A
Tag supported	Ultralight, NTAG203, MIFARE Mini, MIFARE ™ Classic 1K, 4K MIFARE Classic ™, FM11RF08
Interface	I2C
Supply voltage	4.4 - 7.0VDC
Dimension	65 × 45 mm

To communicate with Arduino, Marc Boon had developed the SL018 library for Arduino which support reading UID of tags and reading/writing tags.

 

Stand alone Stronglink SL018 module
By supplying 5V to the SL018 module, the module is able to detect Mifare RFID tags without connecting to the controller such as Arduino. L3 LED will turn on if a Mifare RFID tag is detected within range, 3V appear at Pin1 (Tags) if measured from GND.

 

 

Install the SL018 library for Arduino

• Download the SL018 library, it supports SL030 RFID module as well.
• Extract the Zip file (RFIDuino-master.zip)
• Copy the SL018 folder to the libraries folder of Arduino as shown in figure below

 

 

 

Verify SL018 library is installed correctly

• Launch the Arduino software, I'm using Arduino 1.0.4
• You will be able to see the SL018 examples as shown in figure below if everything is working correctly.

 

 

Upload sketch to Arduino
Marc Boon RFID library included examples for reading the UID of tags.

#include <Wire.h>
#include <SL018.h>
SL018 RFID;
int led = 13;
 
void setup()
{
  pinMode (LED, OUTPUT); 
  Wire.begin (); 
  Serial.begin (19200);
  Serial.println("Show me your tag");   // prompt for tag
}
 
void loop () 
{ 
  rfid.seekTag ()    / / start the seek mode
  while (! rfid.available ())    / / wait until detected tag
  Serial.println (rfid.getTagString ());   / / print some id
}

 

Connecting SL018 RFID module to Arduino
AL018 uses i2c for communication, only two signal is used (Pin2 and Pin3). Connect the SL018 and Arduino based on table below:

SL018	Arduino
1 (TAG)	A3 (Analog 3)
2 (SDA)	A4 (Analog 4)
3 (SLC)	A5 (Analog 5)
4 (VCC)	VCC
5 (GND)	GND

Notice that table above shows Pin1(Tag) is connected to Arduino, but it is not using in this example.

 

 

SL018 RFID module communicate with Arduino

• Connecting SL018 and Arduino based on table above
• Launch the Arduino software
• L3 LED will turn on if Mifare tag detected within range, the UID of the tag will appear in the Serial Monitor (make sure baud rate is 19200) as shown in figure below.

 

 

Code below demonstrate an LED will turn on if verification is passed, LED will turn off after 3 seconds.

#include <Wire.h>
#include <SL018.h>
SL018 rfid;
int led = 13;  // Pin 13 has an LED connected on most Arduino boards
String cardUID;
 
void setup()
{
  pinMode(led, OUTPUT);  // initialize the digital pin as an output.
  Wire.begin();
  Serial.begin(19200);
  Serial.println("Show me your tag"); // prompt for tag
}
void loop()
{
  rfid.seekTag();  // start seek mode
 
  while(!rfid.available());  // wait until tag detected
  cardUID = rfid.getTagString();
  Serial.println( cardUID);  // print tag id
  if ( cardUID == "0467CB11E20280") {
     digitalWrite(led, HIGH);   // turn the LED on
     delay(3000);  //wait for 3 seconds
     digitalWrite(led, LOW);   // turn the LED off
  }
}