Sampling at 8kHz

[Morgan]

Hi

I'm using a 20MHz clock on a Pic16F876 and need to sample analog input (sound) at exactly 8kHz. I know I have to use the timer interrupt as I want to do other stuff while I'm waiting, but don't know how to do this. Would appreciate it if anybody could help me.

Thanx
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This message was ported from CCS's old forum
Original Post ID: 144516386

[R.J.Hamlett]

:=Hi
:=
:=I'm using a 20MHz clock on a Pic16F876 and need to sample analog input (sound) at exactly 8kHz. I know I have to use the timer interrupt as I want to do other stuff while I'm waiting, but don't know how to do this. Would appreciate it if anybody could help me.
:=
:=Thanx

I'd suggest:

int16 ADvalue;

#INT_TIMER2
void T2INT(void) {
ADvalue=read_adc(ADC_READ_ONLY);
read_adc(ADC_START_ONLY);
}

In main:

setup_timer_2(T2_DIV_BY_1,125,5);
enable_interrupts(INT_TIMER2);
enable_interrupts(GLOBAL);

and obviously set the ADC to the required channel, and setup as required.

The timer will be called 20000000/(4*125*5) times per second, and immediately reads the ADC value, from the _last_ conversion, and triggers the next conversion. This way, the interrupt code, doesn't have to wait for the ADC hardware.
You will also have to set a flag in the interrupt, to tell the main code to store the number.

Best Wishes
___________________________
This message was ported from CCS's old forum
Original Post ID: 144516389