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asmboy
Joined: 20 Nov 2007
Posts: 2128
Location: albany ny
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| PIC 18Fxxxx 12 Bit A/D support |
 Posted: Thu Nov 25, 2010 8:58 pm |
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Just had to use a 12 bit internal PIC A/D on an upgrade-a 16F886 design.
Problem is - I can't make the compiler hand me over a proper 12bit conversion without working around the intrinsic A/D functions!
BTW-
#device ADC=12 does NOTHING
I did solve it but there is no syntax in the main compiler that I can make do ANYTHING except return an 8 BIT low order byte and nothing else.
Yes, solved, but its ugly.
Can anybody tell me why the compiler seems not to handle this part right?
| Code: |
version 4.085 compiler
#include <18f2523.h>
#Fuses RC_IO,NOPROTECT
#Fuses BROWNOUT,NOWDT,BORV43
#Fuses PUT,NOCPD,STVREN,NODEBUG
#Fuses NOLVP,NOWRT,NOWRTD,NOIESO,NOFCMEN
#Fuses NOPBADEN,CCP2C1,NOWRTC,NOWRTB,EBTR
#Fuses NOEBTR,NOEBTRB,NOCPB,NOLPT1OSC,NOMCLR,NOXINST
// done in the INIT section already
// using 8 mhz int RC clock no multiplier
// A/D setup
setup_adc( ADC_TAD_MUL_8|ADC_CLOCK_INTERNAL ); // 4 usec
setup_adc_ports( AN0_TO_AN4|VSS_VDD); // R3
set_adc_channel( 3 ); // continuous read DC signal detector 0-5v
unsigned int16 adcout;
void adcll(void){ // get a 12 bit adc reading
unsigned int8 cpr=255;
#byte adhi = 0xFC4
#byte adlo = 0xFC3
read_adc(ADC_START_ONLY);
do {--cpr; } while (!adc_done() && cpr);
if (!cpr) baddie(88); // an error message reporter
else delay_cycles(4);
adcout = adlo + (adhi*256);
}
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Nov 25, 2010 10:42 pm |
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Try a more simple program:
| Code: |
#include <18F2523.h>
#device adc=16
#fuses INTRC_IO,NOWDT,PUT,BROWNOUT,NOLVP
#use delay(clock=4000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
#byte ADCON2 = getenv("SFR:ADCON2")
#bit ADFM = ADCON2.7
#define right_justify_adc() ADFM = 1
//======================================
void main(void)
{
int16 result;
setup_adc_ports(AN0_TO_AN4 | VSS_VDD);
setup_adc(ADC_CLOCK_DIV_4);
right_justify_adc();
set_adc_channel(3);
delay_us(20);
while(1)
{
result = read_adc();
printf("%lx \n\r", result);
delay_ms(500);
}
} |
Also, the output impedance of your analog voltage source must be no
more than 2.5K ohms. |
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asmboy
Joined: 20 Nov 2007
Posts: 2128
Location: albany ny
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| code flips |
| Posted: Fri Nov 26, 2010 7:59 am |
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new code to be tried later today
i am much more at home with hardware -oh for about 35 years -
the A/D port is fed from the output of a buffer op amp.
input Z not involved
the conversions results are dead-on accurate with the code shown -
but using CCS defaults -ONLY the low 8bits are passed back
more later |
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asmboy
Joined: 20 Nov 2007
Posts: 2128
Location: albany ny
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| update |
| Posted: Fri Nov 26, 2010 8:15 am |
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Sorry I also already had the code below in my original init zone.
I was already doing what you suggested - but forgot to extract and show that bit of code.
I was using -
#bit ADFM 0xFC0.7 // adcon2 on the 18fxxxx
then globally
ADFM=1;
STILL the intrinsic A/D functions return ONLY the low 8 bits of the 12 bit conversion - into the 16 bit variable. If I use the CCS built-in call - 8 bits
with the direct register reading code - 12 good bits.
I think its bugs in the compiler version I'm using. Now more than ever.
And the fix I am using works fine - so I chalk it up to another bump in CCS device handling. |
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