ADC *** Locked. 2004 thread.

[Guest]

The problem is:

int var = 10;
float resul;

resul = (float)var;

and i get resul =.166e-41

either ice2000 and icd2.
Why?

I always have the problems with ice2000 about the return of read _adc() that is wrong.

[Guest]

[xinyh]

Hi Ttelmah, Haplo and all,

It's working now. What I did is as below:

1. Rebuilt the project by PIC wizard;
2. Define value as "Long int value";
3. float = (float)value*(5.0/1024.0); don't use value*(5/1024).

Thanks for your valuable guidance.
Best Regards,
Xinyh

[Tony]

Hi,
i'm following the suggestion but it doesn't work.
The code is :

#include <18F452.h>
#DEVICE ICD=TRUE
#DEVICE ADC=10
#include <MATH.H>
#USE FAST_IO(A)
#FUSES HS, NOPROTECT, NOPUT, NOBROWNOUT, NOWDT, NOCPD #USE DELAY (CLOCK=8000000)
#ZERO_RAM

void main()
{
long int value;
float result;

/* Configuration for A/D */
setup_port_a(ALL_ANALOG);
setup_adc_ports(ALL_ANALOG);
setup_adc(ADC_CLOCK_INTERNAL);
/* Port A.0 in input */
set_tris_A(0x01);

while(TRUE)
{
set_adc_channel(0);
delay_us(10);
/* Read the value by A/D internal of PIC18F452 */
value = read_adc();
/* Calculate result in floating point */
result = (float)value*(5.0/1024.0);
}
}

I'm working by MPLAB 6.40 & CCS 3.177.

Vdd = 3V; VinA/D = 0.756V;
ICE2000 : value = 156 (W R O N G!!!!!)
ICD2 : value = 263 (C O R R E C T)
Why this difference?

Either ICE2000 and ICD2 i get result = .599969e-41 instead of 1.284.

Anyone can i help me???
It's IMPORTANT & URGENT!!!!!

Thanks
Tony








}

[rwyoung]

[tony]

Thanks, so what do you suggest?

I have to buy CCS 3.190?

[rwyoung]

Did the 0.0488 multiply work for you?

As a mater of personal preference, I avoid the division operator no mater what processor or compiler I'm using.
_________________
Rob Young
The Screw-Up Fairy may just visit you but he has crashed on my couch for the last month!

[ingemilo]

printf("\n\r ADC-value: %4X \r\n", value);

Here you will get an hexadecimal number

Why don't change as below

printf("\n\r ADC-value: %4Ld \r\n", value);

[ingemilo]

[temtronic]

Hang on... you've got a worse problem !!
According to your program....PIC is 18F452, VDD is 3 volts...

The PIC18F452 is NOT rated to have a VDD of 3 volts!! Check out figure 22-1 of the datasheet. Yes, some individual PICs seem to work OK with an out of spec VDD but they will give random or odd results, quirky performance or just 'die' for some unknown reason.

Check the electrical specs, figure 22-1 in the datasheet. This is important!

You have 2 options
1) buy the 'L' version of the PIC. it IS rated for 3 volt operation,but read the datasheet-do the math, it will NOT run at 40MHz at 3V, more like 12MHz.

2) Use a VDD of 5 volts. The 18F452 WILL work fine then,at full speed of 40 MHz !!


Jay

[ezflyr]

Hi,

You guys (ingemilo & temtronic) do realize that you are posting on a twelve year old "zombie" thread, right???????
_________________
John

If it's worth doing, it's worth doing in real hardware!