Hardware Reference
In-Depth Information
Tweets from RFID
You've seen RFID readers in action, but
there are some RFID tags that can be
written to as well. In the first part of this
project, you'll use the popular Mifare
standard RFID read/write tags and a
SonMicro high-frequency reader to write
Twitter handles to tags. In the second part,
you'll build a microcontroller-based reader
to read the data from those tags and
display it on a 2x16-character LCD display.
This links the physical identity of an RFID
tag to your network identity on Twitter.
MATERIALS
» 1 SonMicro SM130 RFID read/write module
» 3 Mifare RFID read/write tags
» Arduino Ethernet module
» 1 RFID shield
» 13.56MHz antenna
Unless your reader
incorporates an antenna
The parts for building the reader circuit without a shield are listed
below, for those who prefer that option:
» 2 4.7-kilohm resistors
» 1 solderless breadboard
The Circuit
The SonMicro SM130 RFID reader operates on 5 volts, and
it can communicate with a microcontroller using either
asynchronous serial communication or synchronous serial
via I2C. You'll see both in practice in this project. For the
first part, you'll communicate with Processing directly
using asynchronous serial. In the second part, you'll com-
municate with the microcontroller directly using I2C.
RFID tags are often used for more than just the serial
number stored on them. In some mass-transit systems,
the customer's available balance is read from, decre-
mented, and written to the card with each transaction.
Some conferences use the RFID tag to store business card
information, so attendees can exchange data digitally by
tapping their cards to a reader.
Near field communica-
tions
(NFC)
enhances this kind of exchange even further.
NFC involves both passive and active exchange, where
two devices communicate with each other over short
distances. NFC accommodates a number of communica-
tions standards, including some of the RFID standards
like ISO14443A and B, which includes Mifare. Because of
this, NFC devices are often compatible with Mifare RFID
readers and tags. It is starting to gain popularity in mobile
phones and other portable devices, so look for many NFC
and RFID applications in the near future. Projects like this
one here may become relatively commonplace.
There are two Arduino shields available to connect the
SM130 to an Arduino: the TinkerKit RFID shield and the
Spark Fun RFID Evaluation shield 13.56MHz. Both allow
you to connect to either the asynchronous serial or the I2C
connections. The Spark Fun board uses solder jumpers,
which let you choose whether to connect to digital pins 7
and 8 for a software serial connection. The TinkerKit shield
has a switch that turns the serial connection hardware on
or off. The Spark Fun comes with a built-in antenna. The
TinkerKit shield has connections for an external antenna
so you can place it where you wish, relative to the board.
To communicate with Processing, you could use a USB-to-
Serial adapter, like you've done with many other projects,
or you could use the Arduino as a USB-to-Serial adapter.
For the Spark Fun board, you would need to include a
sketch to pass the software serial data to the hardware
serial, and vice versa. For the TinkerKit board, you would
need to switch the serial switch to ON and put a blank
sketch on the board. Both sketches are shown below.
