please help me here...

[hhyong99]

#include <p18f452.h>
#include <adc.h>
#include <delays.h>
#include <stdlib.h>
#include <usart.h>

#pragma romdata CONFIG
_CONFIG_DECL(_CONFIG1H_DEFAULT & _OSC_HS_1H,
_CONFIG2L_DEFAULT & _BOR_ON_2L & _BORV_42_2L,
_CONFIG2H_DEFAULT & _WDT_OFF_2H,
_CONFIG3H_DEFAULT,
_CONFIG4L_DEFAULT & _LVP_OFF_4L,
_CONFIG5L_DEFAULT,
_CONFIG5H_DEFAULT,
_CONFIG6L_DEFAULT,
_CONFIG6H_DEFAULT,
_CONFIG7L_DEFAULT,
_CONFIG7H_DEFAULT);
#pragma romdata

int result ;

void main(void)
{

OpenADC(ADC_FOSC_32 &
ADC_LEFT_JUST &
ADC_1ANA_2REF,
ADC_CH0 &
ADC_INT_OFF) ;

OpenUSART(USART_TX_INT_OFF &
USART_RX_INT_OFF &
USART_ASYNCH_MODE &
USART_EIGHT_BIT &
USART_CONT_RX &
USART_BRGH_HIGH, 129) ;

while(1)
{
Delay10TCYx(5) ;
ConvertADC() ;
while( BusyADC() )
;

result = ReadADC() ;

WriteUSART(result) ;
putsUSART(" ~ ") ;
while( BusyUSART() )
;
}

}


i want to send in a 1kHz sine wave, A/D it and send the result to pc...
i'm running PIC at 20MHz... what baud rate should i set to?? will there be any problem to convert and send data to pc directly??
thank you for helping~~

[Mark]

Note to others: This code is for the C18 compiler.

Note to poster: What sampling rate do you require?

[MikeValencia]

Are you sure you're using the CCS compiler? With all these #pragmas, looks like you're using the Hi-Tech compiler.

Edited:

Oh, I see Mark has pressed "submit" a few seconds before me. I don't know if it's just because it's the day after a 3-day weekend, but there is a LOT of confusion in today's posts so far this morning

[hhyong99]

sorry, i'm using C18 compiler...
how to define sampling rate in programming code?? if i want to sample 1kHz sine wave, at least i need 2kHz sampling rate, right?? but in the code, i'm using 9600 baud rate, should i change this??
thank you for still helping me...

[Mark]

A 2KHz sample on a 1KHz signal would not be very good. Think about it. Can you represent a sine wave with 2K/1K = 2 points?

[hhyong99]

haha... Mark, you are right indeed... then what's the best sampling rate for this??

[Ttelmah]

The minimum sample rate, using conventional sampling for intelligable speech, is in the order of 4500 samples per second, and this is _borderline_.
I'd suggest you look at having an interrupt every 1/10000th second, and on alternate interrupts, start the ADC, and on the next one, read it. Thi would allow 5000 samples/sec.
As for how to do this, you need to go and ask on a C18 forum. This forum is for CCS C, and though some parts are 'generic', details of how to handle tight timings, and interrupts, are specific to the compiler.

Best Wishes

[hhyong99]

Ttelmah, must i have adc interrupt for this?? cos i don't really know how that's work...
thank you...

[Mark]

[hhyong99]

i know what is ADC... but i don't know whether to use ADC or timer interrupt for that...

if i want to set my sampling rate at 10kHz, osilloscope the result of the convertion at the one of my output pin, can that be done?? how can i send the data to the output pin??

[Ttelmah]

The basic answer to what you have now asked, is probably 'no'.
Though this is still the wrong forum, I will answer, since other people using the CCS compiler may well want to do a similar thing.
The first thing to understand, is that your sampling _must_ be regular. Any change in the sample rate, will result in a change in the frequencies represented by the data. Hence I suggested sampling at 5KHz, but using a timer ticking at 10KHz. What you do, is at the first 'tick', start the ADC reading, then at the second, take the result. This you then send to the outside world. Then repeat. Using a serial port at 57600bps, you could just send the data in the time before the next sample, and the rate will be regular. The output data however this will be as a serial stream, and will not be something that would make much/any sense watched on an oscilloscope.
The problem will be _time_, and the amount of data involved. Since there will be 8bits of data at every sample, there will be 40000 bits/second of data. Using 10KHz instead of 5KHz, gets very tight on finding enough time to take the reading and send it.
Proper analog sampling chips, use 'delta' modulation (only recording the change from the last sample), to keep the data rate down.
Unless you are going to write this in CCS C, please go and ask your questions on a C18 forum.

Best Wishes