adc output problem in pic18f4550.

[hiren.dave@bhuved.com]

hi,

my ADC program runs successfully for internal vref. I am taking output of accelerometer. when i changed my Vref+ and Vref- from internal to external. But there is one problem. problem is when input voltage is given to pic it gives 0v as output and when no input is given, it gives maximum voltage at output... my code is also given.

#define USE_OR_MASKS
#include "delays.h"
#include "p18f4550.h"
#include "adc.h"
#include "math.h"


#if defined(_18F4550) //If the selected device if PIC18F46J11, then apply below settings else user will have to set
#pragma config OSC=HS, FCMEN=Off, WDT=OFF, IESO=OFF, XINST=OFF, LVP=OFF
#endif


unsigned int ADCResult=0;
float voltage_x=0;
float theta_x = 0;
float degree_x = 0;

float voltage_y=0;
float theta_y = 0;
float degree_y = 0;


//float voltage_z=0;
//float theta_z = 0;
//float degree_z = 0;
//
//char M[];
//char N[];
void main(void)
{

unsigned char channel=0x00,config1=0x00,config2=0x00,config3=0x00,portconfig=0x00,i=0;
unsigned int final_output,h,d,X=0;
d = 1;
// unsigned int i1=i2=i3=i4=i5=i6=i7=i8=i9=i10=0;
//unsigned int i1=0,i2=0,i3=0,i4=0,i5=0,i6=0,i7=0,i8=0,i9=0,i10=0;





h = 0;
TRISD = 0;
PORTD = 0xFF;
TRISAbits.TRISA0 = 1; //RA) as Analog i/p
PORTAbits.RA0 = 1;
CloseADC();
Delay10TCYx(4);
//--initialize adc---
/**** ADC configured for:
* FOSC/32 as conversion clock
* Result is right justified
* Aquisition time of 2 TAD
* Channel 0 for sampling
* ADC interrupt off
* ADC reference voltage from VDD & VSS
*/
// config1 = ADC_FOSC_16 | ADC_RIGHT_JUST | ADC_2_TAD ;
// config2 = ADC_CH0 | ADC_INT_OFF | ADC_REF_VDD_VSS ;
// portconfig = ADC_2ANA ;
//OpenADC(config1,config2,portconfig);


//---initialize the adc interrupt and enable them---
ADC_INT_DISABLE();

//---sample and convert----
//for(i=0;i<10;i++)
while (d=1)
{




config1 = ADC_FOSC_16 | ADC_RIGHT_JUST | ADC_2_TAD ;
config2 = ADC_CH0 | ADC_INT_OFF | ADC_REF_VREFPLUS_VREFMINUS ;
portconfig = ADC_1ANA ;
OpenADC(config1,config2,portconfig);

ADC_INT_DISABLE();


Delay10TCYx(5);

ConvertADC();

while(BusyADC());

Delay10TCYx(4);
ADCResult = ReadADC();

final_output = ADCResult;

voltage_x = (final_output*2.0)/1023;


theta_x = asin ((voltage_x-1.65)/0.8);

degree_x = theta_x * 57.2957795;



CloseADC(); //turn off ADC

Delay10TCYx(100);
}

}




so hep me to solve this error

 

[Ian Rogers]

What version of C18 are you running..... I have had MAJOR issues with OR / AND masks in the ADC.h file.......Can you simulate it in MPLAB and look at the ADCON0 & ADCON1 registers AFTER the initialization. Just for your reference... Mine were all inverted... I had to write to the ADCON registers separately.

It may not be YOUR issue but it's worth looking into.

I am running the latest version and I have since replaced the ADC.h with an earlier version, It now works for me