RFID Project Help, problem in C source code

[Carnal]

RFID Project Help

I am doing a project using the parallax 125 Khz RFID reader and I need some help with the code to compare the tag data to the data stored in memory. I am using the PIC18F458 with the CCS compiler. I am using strcmp to compare the two values, but it automatically goes to the else statement I have. Here is what I have for the RFID portion of the project:

#include <18F458.h>
#include <stdlib.h>

#fuses NOWDT
#fuses HS
#fuses NOOSCSEN
#fuses BROWNOUT
#fuses BORV27
#fuses NOPUT
#fuses DEBUG
#fuses NOLVP

#use delay (clock=10M)
#use rs232 (baud=2400,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8)

#include <stdlib.h>
#include <string.h>


char readin[11]="1100B8E8D1";          //RFID Tag ID
char check[11];
int length, h;

void rx()
{
int i;

	length=strlen(readin);
	
	for(i=0;i<length;i++)
	{
		check[i]=getc();
	}

	if(strcmp(readin, check) == 0)
	{
		output_high(PIN_D0);
		delay_ms(500);
		output_low(PIN_D0);
		delay_ms(500);
		h=1;
	}
	else{
		output_high(PIN_C3);
		delay_ms(500);
		output_low(PIN_C3);
		delay_ms(500);
		h=0;
	}
return;
}


void main(void)
{
	while(TRUE)
	{
	while(input(mode)==automatic)
		{
		if(kbhit())
		{
		rx();
			if(h==1){
				auto_up();
				delay_ms(5000);
				auto_down();
				delay_ms(500);
				h=0;
					}
			}	
		}
	}
}

I am pretty sure the main function is acting fine because if I just throw a getc() it will do what I want it to. I just do not see why the compare is not working appropriately. Any help would be greatly appreciated.

 

[FvM]

Re: RFID Project Help

You're not setting the terminating \0 for check[], don't know if variables are zerod with CCS as recommended by the C standard? If not, the compare would fail.

Otherwise, the read character string is different from "1100B8E8D1". If so, you can't really expect forum members to know why!

 

[Slayerza]

Re: RFID Project Help

Check the datasheet of the RFID reader you are using to determing the format of the data that the device returns. It is entirely possible the the null termination is giving you some headaches.

Cheers
Slayer

 

[Carnal]

Re: RFID Project Help

You guys were right it was basically the null termination. It works fine now thanks a lot for your help!

 

[etuc_qa]

Re: RFID Project Help

can u give me ur sample code for ur proj?

i am looking for a code that i could test using vb for rfid reader...pls send to jerries_27...tnx...take care!gudluck