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PIC16F819 Analog Input Problems

 
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PIC16F819 Analog Input Problems
PostPosted: Thu Apr 28, 2005 11:56 am     Reply with quote

Question:
I am using a PIC16F819 and programming using the CCS C software. I want to use all of my analog inputs (7). However, when I try to read AN6 and AN7, the value for AN4 is returned. No matter what I try this is what occurs. I am using an internal oscillator. Any suggestions?
Thanks.
guest
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Additional Info
PostPosted: Thu Apr 28, 2005 12:03 pm     Reply with quote

More information:
I am using the code:

set_up_ADC(all_analogs);

however I see that this only allows for AN0-AN5, how can I change that to allow for the whole bank of analog inputs?
Thanks.
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Thu Apr 28, 2005 12:03 pm     Reply with quote

Quote:
When I try to read AN6 and AN7, the value for AN4 is returned.

1. What is your compiler version ?

2. Post a small test program that shows the problem.

Be sure to post all of your #include statement, #use statements,
#fuses statement, and make it be a complete program with a main(),
so it can be compiled. (Don't just post code fragments).
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CODE
PostPosted: Thu Apr 28, 2005 12:05 pm     Reply with quote

#include <16F819.h>

#device ADC=8
#include <math.h>
#fuses NOWDT,NOPROTECT,NOLVP,PUT,INTRC_IO
#use delay(clock=8000000)
void main() {
setup_oscillator(OSC_8MHZ); //set INTRC to prescaler of 8MHz
set_TRIS_A(0xFF); //PORTA setup 0b11111111
set_TRIS_B(0x00); //PORTB setup 0b00000000
setup_ADC_ports(ALL_ANALOG);
setup_ADC(ADC_CLOCK_INTERNAL);
}

That is the section of code relating to this problem. All of the read analog part is workin fine.
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Thu Apr 28, 2005 12:27 pm     Reply with quote

Quote:
I am using a PIC16F819 and programming using the CCS C
software. I want to use all of my analog inputs (7).

Look at the data sheet for the 16F819.

It only has 5 analog pins: AN0-AN4

Pins RA5, RA6 and RA7 are digital i/o only.
guest
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That would make sense
PostPosted: Thu Apr 28, 2005 12:35 pm     Reply with quote

My bad. I completely read that data sheet wrong. Looks like it is time for some 'engineering' around this issue.
Thanks.
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