PIC18F4520 – Interfacing EM-18 compatible μRFID

The PIC18F4520 Mini Development Board provides on board support for interfacing μRFID reader. Radio-frequency identification (RFID) technology enables remote and automated gathering and sending of information between RFID tags or transponders and readers using a wireless link.Using RFID the exchange of data between tags and readers is rapid, automatic and does not require direct contact or line of sight. The RFID module can be interfaced with the board using the same serial reception program used for testing the UART. When a Card (tag) is brought near the RFID reader, it tries to communicate with the tag, receives the data and decodes it. Finally it send the data over the Tx line. The UART module in MCU receives the data and thus used for further applications.

Schematic

Sample Code

The sample code to interface μRFID reader is given below. On reading an RFID card, its ID is displayed on LCD.

/*************************************************************************
                           HEADER FILES
**************************************************************************/
#include<pic18.h>    

/*************************************************************************
                       FUNCTION DECLARATIONS
**************************************************************************/
void Delay_us(char Delay);
void Delay_100us(unsigned long int Delay); 
void Data(char Value);              
void Cmd(char Value);               
void Send2Lcd(const char Adr, const char *Lcd);

/*************************************************************************
                       VARIABLE DECLARATIONS
**************************************************************************/
int bx=0,rfid=0,i=0;
char msg[14],R=0;

/*************************************************************************
                           MAIN FUNCTION
**************************************************************************/
void main()                     
{
 TRISC = 0X80;                /* RC7(Rx) configured as i/p, 
                                 RC0(RS),RC1(EN) as o/p                  */
 TRISD = 0X00;                /* PORTD(data lines) configured as o/p     */
 Delay_us(35); 
 Cmd(0X30);                   /* LCD Specification Commands              */
 Delay_us(35);
 Cmd(0X30);                   /* LCD Specification Commands              */
 Delay_us(35);
 Cmd(0X30);                   /* LCD Specification Commands              */
 Delay_us(35);
 Cmd(0X38);                   /* Double Line Display Command             */
 Cmd(0X06);                   /* Auto Increment Location Address Command */
 Cmd(0X0C);                   /* Display ON Command                      */
 Cmd(0X01);                   /* Clear Display Command                   */
 Delay_100us(30);
 Send2Lcd(0x80,"   rhydoLABZ    ");
 Send2Lcd(0xc0,"   RFID TEST    ");
 TXSTA = 0X24;
 RCSTA = 0X90;
 SPBRG = 0X81;

 while(1)
 { 
  while(RCIF==0);             /* Wait here till data is received         */
  RCIF = 0;                   /* Clear Receive interrupt flag            */
  R = RCREG;                  /* Copy the received character             */
  msg[bx] = R;                /* Store the ID no: in an array            */
  bx++;                       /* Increment the array index               */	
  if(bx==12)                  /* Check if all the 12 numbers are received*/
  {
   msg[bx]='\0';              /* Terminate the string with null character*/
   bx=0;                      /* Clear array index                       */
   Cmd(0xC2);
   for(i=0; msg[i]!='\0'; i++)/* Display the no: on LCD                  */
   {
    Data(msg[i]);
   }
   Delay_100us(15000);Delay_100us(15000);
   Send2Lcd(0xc0,"   RFID TEST    ");			 
  }
 }
}

/*************************************************************************
* Function    : Cmd                                                      *
*                                                                        *
* Description : Function to send a command to LCD                        *
*                                                                        *
* Parameters  : Value - command to be sent                               *
**************************************************************************/
void Cmd(int Value)
{
 PORTD = Value;               /* Write the command to data lines         */
 RC0   = 0;                   /* RS-0(command register)                  */
 RC1   = 1;                   /* E-1(enable)                             */
 Delay_us(25);                
 RC1   = 0;                   /* E-0(enable)                             */
}

/*************************************************************************
* Function    : Data                                                     *
*                                                                        *
* Description : Function to display single character on LCD              *
*                                                                        *
* Parameters  : Value - character to be displayed                        *
**************************************************************************/
void Data(int Value)
{
 PORTD = Value;               /* Write the character to data lines       */
 RC0   = 1;                   /* RS-1(data register)                     */
 RC1   = 1;                   /* E-1(enable)                             */
 Delay_us(25);                
 RC1   = 0;                   /* E-0(enable)                             */
}

/*************************************************************************
* Function    : Send2LCD                                                 *
*                                                                        *
* Description : Function to display string on LCD                        *
*                                                                        *
* Parameters  : loc - location                                           *
*               String to be displayed                                   *
**************************************************************************/
void Send2Lcd(const char Adr, const char *Lcd)
{
 Cmd(Adr);                    /* Address of location to display string   */
 while(*Lcd!='\0')            /* Check for termination character         */
 {	
  Data(*Lcd);                 /* Display the character on LCD            */	
  Lcd++;                      /* Increment the pointer                   */
 }
}

/*************************************************************************
* Function    : Delay_us                                                 *
*                                                                        *
* Description : Function for 1 microsecond delay                         *
*                                                                        *
* Parameter   : Delay - delay in microseconds                            *
**************************************************************************/
void Delay_us(char Delay)    
{		
 while((--Delay)!=0);	
}

/*************************************************************************
* Function    : Delay_100us                                              *
*                                                                        *
* Description : Function for delay                                       *
*                                                                        *
* Parameter   : Delay - delay in microseconds                            *
**************************************************************************/
void Delay_100us(unsigned long int Delay)
{
 Delay=Delay*15;
 while((--Delay)!=0);
}

/***************************  END OF PROGRAM  ****************************/

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/*************************************************************************

HEADER FILES

**************************************************************************/

#include<pic18.h>

/*************************************************************************

FUNCTION DECLARATIONS

**************************************************************************/

void Delay_us(char Delay);

void Delay_100us(unsigned long int Delay);

void Data(char Value);

void Cmd(char Value);

void Send2Lcd(const char Adr, const char *Lcd);

/*************************************************************************

VARIABLE DECLARATIONS

**************************************************************************/

int bx=0,rfid=0,i=0;

char msg[14],R=0;

/*************************************************************************

MAIN FUNCTION

**************************************************************************/

void main()

{

TRISC = 0X80; /* RC7(Rx) configured as i/p,

RC0(RS),RC1(EN) as o/p */

TRISD = 0X00; /* PORTD(data lines) configured as o/p */

Delay_us(35);

Cmd(0X30); /* LCD Specification Commands */

Delay_us(35);

Cmd(0X30); /* LCD Specification Commands */

Delay_us(35);

Cmd(0X30); /* LCD Specification Commands */

Delay_us(35);

Cmd(0X38); /* Double Line Display Command */

Cmd(0X06); /* Auto Increment Location Address Command */

Cmd(0X0C); /* Display ON Command */

Cmd(0X01); /* Clear Display Command */

Delay_100us(30);

Send2Lcd(0x80," rhydoLABZ ");

Send2Lcd(0xc0," RFID TEST ");

TXSTA = 0X24;

RCSTA = 0X90;

SPBRG = 0X81;

while(1)

{

while(RCIF==0); /* Wait here till data is received */

RCIF = 0; /* Clear Receive interrupt flag */

R = RCREG; /* Copy the received character */

msg[bx] = R; /* Store the ID no: in an array */

bx++; /* Increment the array index */

if(bx==12) /* Check if all the 12 numbers are received*/

{

msg[bx]='\0'; /* Terminate the string with null character*/

bx=0; /* Clear array index */

Cmd(0xC2);

for(i=0; msg[i]!='\0'; i++)/* Display the no: on LCD */

{

Data(msg[i]);

}

Delay_100us(15000);Delay_100us(15000);

Send2Lcd(0xc0," RFID TEST ");

}

/*************************************************************************

* Function : Cmd *

* *

* Description : Function to send a command to LCD *

* *

* Parameters : Value - command to be sent *

**************************************************************************/

void Cmd(int Value)

{

PORTD = Value; /* Write the command to data lines */

RC0 = 0; /* RS-0(command register) */

RC1 = 1; /* E-1(enable) */

Delay_us(25);

RC1 = 0; /* E-0(enable) */

}

/*************************************************************************

* Function : Data *

* *

* Description : Function to display single character on LCD *

* *

* Parameters : Value - character to be displayed *

**************************************************************************/

void Data(int Value)

{

PORTD = Value; /* Write the character to data lines */

RC0 = 1; /* RS-1(data register) */

RC1 = 1; /* E-1(enable) */

Delay_us(25);

RC1 = 0; /* E-0(enable) */

}

/*************************************************************************

* Function : Send2LCD *

* *

* Description : Function to display string on LCD *

* *

* Parameters : loc - location *

* String to be displayed *

**************************************************************************/

void Send2Lcd(const char Adr, const char *Lcd)

{

Cmd(Adr); /* Address of location to display string */

while(*Lcd!='\0') /* Check for termination character */

{

Data(*Lcd); /* Display the character on LCD */

Lcd++; /* Increment the pointer */

}

/*************************************************************************

* Function : Delay_us *

* *

* Description : Function for 1 microsecond delay *

* *

* Parameter : Delay - delay in microseconds *

**************************************************************************/

void Delay_us(char Delay)

{

while((--Delay)!=0);

}

/*************************************************************************

* Function : Delay_100us *

* *

* Description : Function for delay *

* *

* Parameter : Delay - delay in microseconds *

**************************************************************************/

void Delay_100us(unsigned long int Delay)

{

Delay=Delay*15;

while((--Delay)!=0);

}

/*************************** END OF PROGRAM ****************************/

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