Author: Moises Melendez Reyes
RFID-SPI SYSTEM WITH DISPLAY OF DATA ON MOBILE PHONE
RFID-SPI SYSTEM WITH DISPLAY OF DATA ON LAPTOP WITH BLUETOOTH LINK
RFID-SPI SYSTEM WITH DISPLAY OF DATA ON LAPTOP WITH USB-SERIAL CABLE
The so called Syncronous Periferal Interface (SPI) protocol has become a popular technique to transmit information between 2 microcontroller devices at a a high speed, and short distances.
On the other hand, with the emergence of smartphones, which already have their own operating system, it is possible to develop applications using Bluetooth for the wireless links between mobile devices and microcontrollers.
In this project, a Samsung Galaxy mobile is used as a receiver and display of the RFID data. The connection between an MF522 RFID read-write device, (or RC522 RFID), with operating frequency of 13.56 MHz, SPI interface, and a Bolt 18F2550 system is described. The system can be used in the following applications: access control, attendance control, public transportation, parking of vehicles, electronic payment systems, inventory control, and many others.
THE ISO-14443A TAGS:
The MF522 RFID read-write device receives information from an RFID ISO-14443A tag, In this project, a keychain tag (blue color) was used, as shown in the picture above. This card contains an EEPROM with 1 Kb of available space for data.
THE BLUETOOTH LINK:
To establish communication between the microcontroller and the mobile, a bluetooth module HC-06 with serial port, which allows the transmission of RFID data received by the Bolt board to the mobile phone is used. This link, which is a Class 2 in the Bluetooth standard, can operate up to a distance of 10 meters.
TESTING THE SYSTEM:
To test the system, you must assemble the test equipment as shown in the photos above. Its functioning in any of the modes -explained in the following paragraphs- requires that the proper firmware had been previously loaded to the Bolt system.
In all cases, you must bring the tag at an aproximate distance of 5 cms from the MF522 device and remain in that position until you receive a confirmation on the mobile phone. The summary of the system working in each mode is as follows:
Reading the tag: the user brings the tag (blue key) near to MF522 device. At that time, automatically and through SPI communication, the system reads part or all of the EEPROM memory of the tag. This information is sorted, tabulated and transmitted to the serial port in Bolt board, which has already inserted a HC-06 Bluetooth module. The information is transmitted wirelessly from the Bolt system to the mobile phone, where the user can see it.
Erasing data tag: the user brings the tag near to MF522 device. On the mobile phone you will see confirmation of the erasing each sector of the entire EEPROM.
Writing new data to the tag: the user brings the tag near to MF522 device. Automatically, the system will write the new data to the EEPROM of tag, sending confirmation to the mobile phone.
BLUETERM APPLICATION FOR THE MOBILE PHONE:
To display the data read from the RFID tag, the mobile phone must run the application called 'Blueterm', compatible with the Android operating system, which is a terminal emulator application which allows you to send or receive ASCII strings through the Bluetooth link already built into the phone (this application is equivalent to the 'Hyperterminal' software for Windows). This program is free and can be directly downloaded to your mobile phone from the Google Play website.
CONECTION BETWEEN THE BOLT 18F2550 BOARD AND THE MF522, RC522 RFID-SPI CARD:
As shown in the figure above, the Bolt card connects to an external wall transformer, which provides the overall system power. To feed the MF522 RFID card, a 3.3 volt regulator is used. The data transfer between the card and the MF522 Bolt is performed using an interface with the SPI standard. The diagram of connections between the two systems is shown in the figures below:
AVAILABLE FIRMWARE FUNCTIONS:
The firmware functions developed for Bolt system include: reading the serial number of the card or tag, reading the entire EEPROM of tag either in hexadecimal or ASCII format (64 sectors, 4 blocks per sector 768 locations of read/write ), erasing the EEPROM memory, and writing new ASCII text data in the tag.
These functions provide a general basis by which programmers can develop specialized RFID applications aimed at solving specific problems. The programs were developed using the C18 compiler and MPLAB IDE tools.
1. READING DATA FROM THE TAGS EEPROM:
For a general system test, the following program for the Bolt 18F2550 system was developed . This program allows the use of 3 functions, selected by the dip switches on the Bolt card.
*** IMPORTANT *** For the data to be neatly in the screen of your mobile, you need to configure the program 'BlueTerm' as shown in the attached photos, to replace all received CR characters with CRLF. If you omit this step, the characters will appear superimposed and impossible to read.
Open on your mobile the BlueTerm app and choose the following options:
To read data from the tag's EEPROM, download the complete MPLAB-IDE-C18 project here: MFRC522-C18-5.zip. You must load the .hex file to your Bolt board and move the dip switches accordingly to the desired function. The reset button must be pushed to activate any of the functions.
Example of data read from the RFID tag and transmitted to the user on his mobile phone, running BlueTerm application. Data of the EEPROM can be modified using the firmware for Bolt described in point 3.
Reading the tag's serial number:
Reading the tag's EEPROM information in hexadecimal format:
Reading the tag's EEPROM information in ASCII codes:
2. TO ERASE ALL EPROM MEMORY:
Additionally, to erase the memory of the TAG, the following firmware is used. Load the hex file from the following folder to Bolt system.
To completely erase the EEPROM memory of tag: PROJECT-C18-MPLAB-RFID-CLEAR-TAG.zip
3. TO WRITE NEW DATA INTO THE TAGS EEPROM:
Writing new data to the tag requires the user interaction with the MPLAB and C18 compiler tools and modifying the text and then compile the program and load it into the Bolt system, which will send this new data to the MF522 and then to the tag. Please read the instructions described in the source program .c included in the following folder to modify the new data you wish to write to the tag.
To write new data into the EEPROM of tag: PROJECT-C18-MPLAB-RFID-WRITE-EEPROM-TAG.zip
Summary of erase and write funtions:
OTHER RFID RECOMMENDED LINKS: