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16c771

 
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Collison
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16c771
PostPosted: Fri Jul 22, 2005 1:56 pm     Reply with quote
I am having trouble using the ADC on the 16C771. This is a 12 bit adc, but for some reason it is only giving me an 8 bit value. I am thinking that I have to set it up to be 12 bit instead of 8, but the header file that I have does not include anything. Any help on this would be appreciated.

Collison
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Fri Jul 22, 2005 2:12 pm     Reply with quote
Post your version of the compiler.
Collison
Guest
version
PostPosted: Fri Jul 22, 2005 2:20 pm     Reply with quote
MPLAB IDE 5.70.40 or
MPLAB ICE Universal Emulator v2.60.40
Collison
Guest
Sorry, wrong version
PostPosted: Fri Jul 22, 2005 2:28 pm     Reply with quote
The version that I have is v 2.705

Thanks
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Fri Jul 22, 2005 3:55 pm     Reply with quote
Quote:
I am having trouble using the ADC on the 16C771. This is a 12 bit
adc, but for some reason it is only giving me an 8 bit value.


The "#device adc=12" directive doesn't work with your version of
the compiler, so I had to write a routine to read the 12-bit result.
See the code below.
I didn't put in the lines of code to setup the adc port, or to setup
the ADC, or to select the A/D channel, because I don't know what
pin you're using or what your PIC crystal frequency is.
I'll leave that code to you.

Code:
#include "c:\picc\examples\16C771.h"
#fuses XT,NOWDT,NOPROTECT,PUT,BROWNOUT //,NOLVP
#use delay(clock=4000000)
//===================================
#byte ADCON0 = 0x1F
#byte ADCON1 = 0x9F
#byte ADRESL = 0x9E
#byte ADRESH = 0x1E

#bit ADFM_BIT = ADCON1.7
#bit GO_BIT = ADCON0.2
#define BytePtr(var, offset) (char *)(&var + offset)

long read_adc_12_bits(void)
{
long retval;

ADFM_BIT = 1; // Right justify the A/D result
GO_BIT = 1; // Start the A/D conversion

while(GO_BIT); // Wait until conversion is done

*Byteptr(retval,0) = ADRESL; // Get LSB of result
*Byteptr(retval,1) = ADRESH; // Get MSB of result

return(retval);
}

//=================================
void main()
{
long result;

// Put in code here to setup the adc port,
// setup the ADC, and to select the A/D channel.

result = read_adc_12_bits();

while(1);
}
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