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bharatwalia
Joined: 04 May 2009
Posts: 35
Location: India
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| ADC not reading value |
 Posted: Fri Nov 05, 2010 12:44 am |
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The below code is written to read main voltage through PIC16F876A ADC
and store it in a variable, then it compares the stored voltage with a reference voltage stored in another variable and if the read value is greater than stored value than the controller will perform some action based on the given condition.
But in here the problem is that the adc is not reading the voltage, I have checked the hardware its all correct.
| Code: |
#include <16F876A.h>
#device adc=10
#fuses XT,HS,WDT,NOPUT,NOPROTECT
#use delay(clock=20000000, RESTART_WDT)
#use fast_io(A)
unsigned int32 set_point=511,inv_out=0;
//-->(1023==300V)
//-->511==150V
void main()
{
set_tris_a(0XFF);
setup_adc_ports(AN0_AN1_AN3); //Setting ADC Channels
setup_adc(ADC_CLOCK_DIV_64);
set_adc_channel(1); //using channel 1
delay_us(10); //acquisition delay
inv_out=read_adc();
if(inv_out>set_point){
delay_ms(5000);
disable_interrupts(GLOBAL);
delay_ms(5000);
enable_interrupts(GLOBAL);
}
}
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In the above code voltage read is always above 150V and still the condition is false, whereas when I set the value of "inv_out" variable to "600" manually than the condition turns out to be true.
So I think the inv_out variable is not getting any value at execution.
Need suggestions what could be wrong.
Regards. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19535
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| Posted: Fri Nov 05, 2010 3:15 am |
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Several comments:
1) Get your clock fuses right. Currently you are selecting both 4MHz or less oscillator, and >4MHz oscillator. That the chip runs at all, is 'luck'.
2) Do the same with the interrupts. You must _never_ enable the global interrupt without an interrupt handler present. Doing so, has a high risk of simply crashing the code.
3) For your chip, the ADC Tacq, is 20uSec, not 10uSec. This will only make things less accurate, but correct it.
4) You don't show any form of loop, as shown, the code won't actually 'do' anything to show that it is working....
Best Wishes |
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