CP/PC364 Data Communications and Networks Laboratory

Serial RFID Reader (UART)

Overview

This week's laboratory investigates RS-232 (or EIA 232) communication.

Background

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 straightforward. 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 using the serial monitor. 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 otherwise.

Objectives

1. Become familiar with real serial communication using the SoftwareSerial library emulating a UART with an external device.
2. Become familiar with the Arduino serial monitor for interacting with the Arduino.

Equipment

• Arduino Uno board, with LCD display
• RFID reader and tags

Exercise

1. Questions to ask before you start (Consult the data sheet to answer these.):
   1. What Arduino pins will you use for the software serial port?
   2. What baud rate does the RFID reader use? How many data and stop bits?
   3. 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?
2. Connect the Arduino to the RFID reader. Notice there is an additional signal input to the RFID reader that you can simply jumper to power or ground as appropriate to start.
3. Modify the NewSerialPassthrough sketch as needed so you can communicate with the RFID reader.
   
   
4. 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/serial monitor.
   
   
5. Now use an output pin of the Arduino to replace the jumper above, so that the RFID operation is totally handled by the sketch. Be sure not to use any pins already used by the shield for this!
   Hint: remember the Blink sketch has an example of this.
   Modify your sketch so that pressing one of the shield buttons enables the reader and pushing a different button disables it.

Demonstrate and explain your results to the lab instructor