CP/PC364 Data Communications and Networks
Serial RFID Reader (UART)
This week's laboratory investigates
(or EIA 232) communication.
A simple example of a serial device is an RFID reader, since it only
requires communication in one direction.
Since you've already used the Arduino built-in UART,
RS-232 communications with the RFID reader should be
One of the limitations of the Arduino is that if two devices need
serial communication, there is a problem. Fortunately, there is a
SoftwareSerial library that allows a UART to be simulated on other
pins. You'll use this for the RFID reader since you still need to
connect to the console.
Note: The RFID reader is designed for
"TTL serial" operation, which means its pins
will be at TTL levels, not at acceptable RS-232 levels.
Since the UART pins on
the Arduino are also at
TTL levels, this makes the interfacing simpler than it would be
- Become familiar with real serial communication using the
SoftwareSerial library emulating a
UART with an external device.
- Arduino Uno board, with LCD display
- RFID reader and tags
Demonstrate and explain your results to the
- Look at one of the SoftwareSerial examples and figure out how
to set up pins to use for this purpose.
The comments at the beginning of the sketch should indicate
pins that can be used. Choose two
for the software UART and connect them together as in the previous
Modify your previous sketch to
send characters out the TX and in the RX
echo the received
characters to the LCD
display. This should be a pretty minor modification to the
- Questions to ask before you start (Consult the data sheet to
- What Arduino pins will you use for the software serial port?
- What baud rate does the RFID reader use? How many data and
- What pin has data coming out of the RFID reader? Does that
need to go into the TxD or RxD pin on the Arduino? In other
words, when connecting to serial devices, do TxD and RxD of
both match, or do they reverse?
- Connect the Arduino to the RFID reader. Notice there is an
additional signal input to the RFID reader that you can simply
power or ground as appropriate to start.
- Use one of the SoftwareSerial examples
to repeatedly read characters
from the pin you've chosen for the software UART. Send the
characters to the hardware UART.
You can use the
serial monitor to test this and see that it works.
- Once you have it working, create a sketch that incorporates
the LCD software as well so you can display the RFID information
to the LCD display instead of to the hardware UART. It would be
good to use an output pin of the Arduino to replace the jumper
above, so that the RFID operation is totally handled by the sketch.
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