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Trouble Setting a Pin as an Input

 
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ralpok



Joined: 21 Dec 2005
Posts: 25

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Trouble Setting a Pin as an Input
PostPosted: Wed Feb 20, 2013 10:31 am     Reply with quote

I have a project I have started with the PIC10f320 micro controller. I want to just get a simple program running setting Pin1 and GP0 as an input (eventually I want to set it as an Analog input). The problem I am having is that the PIC appears to be driving the pin low, even though I have assigned it to an input. The input right now is being fed by a power supply through a 10k ohm resistor and a 1uf filter cap (tied between signal and Gnd). I checked and the maximum recommended input impedance to be 10kohm. When I apply the analog voltage directly to the PIC instead of through the resistor/cap I get the correct voltage and even the analog reads work correctly but it does pull significant current. This is why I believe I am just not setting the pin up correctly as an input but I have tried setting the PORTA, LATA, TRISA, ports all to the settings I believe they should be. Any help would be great.

The program I have tried to run is:

I am running Win 7:
CCS Studio: PCWHD 4.134

Code:

#case
#include <10f320.h>
#device ADC=8
#fuses NOWDT, INTRC
#use delay (internal=8000000)
#use standard_io(A)

#byte PORTA = 0x05
#byte LATA = 0x07
#byte ANSELA = 0x08
#byte TRISA = 0x06
#byte WPUA = 0x09
#byte ADCON = 0x1f
#byte ADRES = 0x1E


void main()
{
   int8 velocity[10];
   int16 avgVelocity = 0;
   int ndx = 0;
   int8 overRateDetect = 0;
 
   delay_ms(2000);

   PORTA = 0x01;
   LATA = 0x00;
   ANSELA = 0x01;
   TRISA = 0x01;
   WPUA = 0x00;
   ADCON = 0b10000001;

   while (1)
   {
     

   }
}
ralpok



Joined: 21 Dec 2005
Posts: 25

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PostPosted: Wed Feb 20, 2013 10:45 am     Reply with quote

I solved this problem myself but figured I would post the solution in case it helps anybody else. On this PIC the GP0 pin is shared as the ICSP data pin. I was using the CCSLoad to load and run the program but left the programmer plugged in while I was doing the "running". It appears that this was the issue and the programmer was pulling this PIN low during this operation.

Hope this helps
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