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PORTB Problem

 
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cfernandez



Joined: 18 Oct 2003
Posts: 145

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PORTB Problem
PostPosted: Wed Jul 04, 2007 7:55 pm     Reply with quote
Hi,

I use a 18F4620 25Mhz, and I need use the PortB.0 to PortB.4 for digital input. In this pins I connect a Magnetic Card Reader, in the pin 0 connect the card present, this is high when not is a card, and low when exist a card. The problem is that the pin 0 and 1 not is possible to get the 0 or 1 value from the mag. card reader, the other pins work fine. If I put the pin 0 or 1 to ground I see that signal change from 1 to 0.

Why cannot work the pin 0 and 1 from port b for detect digital input??. Any can help me.

This is my test code

Code:
#include <18F4620.h>
#fuses HS,NOLVP,NOWDT,NOPROTECT
#use delay(clock=25000000)
#use rs232(baud=115200, xmit=PIN_C6, rcv=PIN_C7)

#use fast_io( B )

void main()
{
   int index;
   int error;

   port_b_pullups( FALSE );
   set_tris_b( 0xFF );
   
   error = 0x00;
   while( 1 )
   {
        index = input_b( );
       
        if ( index != error )
        {
            printf( "%u%u%u%u%u%u%u%u\n\r", bit_test( index, 7 ), bit_test( index, 6 ), bit_test( index, 5 ), bit_test( index, 4 ), bit_test( index, 3 ), bit_test( index, 2 ), bit_test( index, 1 ), bit_test( index, 0 ) );
            error = index;
        }
   }       
}     


Thank you very much!!
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Wed Jul 04, 2007 10:33 pm     Reply with quote
It may need a pull-up resistor. Post a link to the data sheet of the
card reader.
cfernandez



Joined: 18 Oct 2003
Posts: 145

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PostPosted: Thu Jul 05, 2007 1:23 pm     Reply with quote
I am use a Kit from CCS and in this kit connect my reader, the problem is that this kit have a connector for GPIO, but the PIN 0 and 1 from PORT B is use for the Ethernet Chip and I have not the schematic for see this information. CCS send me a email with this.

Thank you very much PCM for your time.

Best Regards,
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