Security Device using RFID Reader Alex Gerard & Joe Nevin

Outline  For the final Embedded Systems project we designed and implemented the software to enable the ATmega88PA to act as a door security system using: A 125 kHz Radio Frequency Identifier. A RS-232 serial communication with a SecureCRT terminal. HD44870 LCD display

Radio Frequency ID -The RFID reads unique ID's from EM bit RFID compatible tags at 125 kHz (with a 100 mm range). -The ID's are sent from the RFID serially out the TTL data pin. -The TTL pin was connected to the RXD (D0) pin of the Atmega88PA. -The RFID also has pins connected as follows: ~Power to +5 V and Ground to ground ~Reset to ground ~”Format Select” to ground which determines ascii transmission -TTL~Transistor-Transistor Logic: Uses a transistor for the logic gate as well as for the amplifying function.

The USART is first initialized Since the RFID transmits data serially the UDR register is polled constantly in an infinite while loop. When the micro controller receives a character it is stored in an array. This ID is checked to see if they it belongs to an authorized user and whether they are cheecking in or checking out.

RS-232  The RS-232 cable was used to send information regarding the checking in and checking out of the devices users to the SecureCRT terminal. The Atmega88PA's TXD (D1) pin was connected to the MAX232's RX pin to facilitate this transmission. The software initializes the USART and the UDR register is written to. If a valid card is presented, and it belongs to a user of the system, the terminal displays their ID and whether they are checking in/out or if they aren't a user.

HD44870 LCD display The HD44870 LCD display was also used to communicate with the user of the device. First the LCD is initialized then the process goes as follows: “Present Card” is displayed on the LCD. Once a valid card is presented “Card ID: xxxxxxxxxxxx” is displayed for about 5 seconds. The process then restarts.

Demonstration