Reading RFID tags
Original Assignment
Interface your PIC with an RFID reader (see here) and demonstrate recognition of various RFID tags.
Overview
Radio Frequency Identification (RFID)is a generic term used to describe technology that uses radio waves identify objects. The Parallax RFID Card Reader, Serial (#28140) reads passive RFID transponder tags up to 4 inches away from the reader. The RFID communicates using rs232 and transmits a 12-byte ASCII string. The first byte (start byte) is always $0A and the last byte (stop byte) is always $0D. The 10 middle digits are the 10 unique id digits that are unique to every RFID transponder.
Circuit
RFID SOUT to PIC RC7 RFID VCC to PIC +5 RFID GND to PIC GND RFID /ENAMBLE to PIC RC7 PIC RC6 to TTL-232R Yellow Wire (note: this is output signal to view on PC) PIC GND to TTL-232R Black Wire (note: this is connecting the grounds together)
Code
The following code reads in the RFID tag from the RFID Card Reader and then writes it out to a ps232 connection. In our tests we used a TTL-232R with a baud of 2400. This allows you to view the RFID unique ID on the computer.
/*
RFID_Input.c J.Cooper and C.Ryan 2009-2-04
Read in from RFID Card on pin RC7
Write out RFID unique number on pin RC6
*/
#include <18f4520.h>
#fuses HS,NOLVP,NOWDT,NOPROTECT
#use delay(clock=40000000) // 40 MHz crystal on PCB
#use rs232(baud=2400, UART1) // hardware UART; uses RC6/TX and RC7/RX
int16 i;
char value[12];//12 values of tag ID
void main() {
output_low(PIN_D7); //Set enable to low
for (i=0; i<12; i++) { //read in the 12 values
value[i]=getc();
}
printf("rfid# %c %c %c %c %c %c %c %c %c %c \r\n", value[1] value[2] value[3] value[4] value[5] value[6] value[7] value[8] value[9] value[10]); //display 10 unique id digits
}
