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NewSpace
Joined: 23 Sep 2003
Posts: 12
Location: South KOREA
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| Why when I got a data is problem? |
 Posted: Sun Feb 20, 2005 1:12 am |
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Dear Master~!
Hi~
When I got a ADC data is problem
It's about 30-40 is different....
1st 129
2nd 135
3th 110
4th 140
That's same volte
and float data is can't operation.
Please check my code....
Thank you~!
| Code: | #include<16F874.h>
#device pic16f874 *=8 adc=10
#use delay(clock=4000000)
#use rs232(baud=19200,parity=N,xmit=PIN_C4,rcv=PIN_C5)//,ERRORS,stream = PORT1)
#zero_ram
// A0 (02) = [AD] humidity (0.8 - 3.9 V)
// A1 (03) = [AD] Temp (0.0 - 5.0 V)
// A2 (04) = [AD] Vref - (0.8 V)
// A3 (05) = [AD] Vref + (3.9 V)
// A4 (06) =
// A5 (07) =
int16 value = 0;
float humi = 0 , temp = 0;
void Read_Humity()
{
setup_adc_ports(RA0_ANALOG_RA3_RA2_REF);
setup_adc(ADC_CLOCK_INTERNAL);
set_adc_channel(pin_a0);
delay_us(10);
value = read_adc();
setup_adc( ADC_OFF );
humi = ((value*5)/1023);
printf("%c%c%c",0xa1,0,1);
printf("%cAD=%04lu Humi=%02f %c",0xa2, value, humi, 0);
}
void Read_Temp()
{
setup_adc_ports(RA0_RA1_RA3_ANALOG);
setup_adc(ADC_CLOCK_INTERNAL);
set_adc_channel(pin_a1);
delay_us(10);
value = read_adc();
setup_adc( ADC_OFF );
temp = ((value*5)/1023);
printf("%c%c%c",0xa1,0,2);
printf("%cAD=%04ld Temp=%02f%c",0xa2, value, temp, 0);
}
void main()
{
ext_int_edge(0,L_TO_H);
enable_interrupts(int_ext);
enable_interrupts(global);
// 7 6 5 4 3 2 1 0
set_tris_a(0x3F); // I I I I I I
set_tris_b(0xFF); // I I I I I I I I
set_tris_c(0x00); // O O O O O O O O
set_tris_d(0x00); // O O O O O O O O
set_tris_e(0xFF); // I I I
output_c(0x00);
output_d(0x00);
output_e(0x00);
while(1)
{
Read_Temp();
Read_Humity();
delay_ms(1000);
}
} |
_________________
Hello~?
This is South KOREA
My name is Sanghyouk Kim But Call me Nick
Sorry I'm poor English |
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libor
Joined: 14 Dec 2004
Posts: 288
Location: Hungary
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| Posted: Sun Feb 20, 2005 6:23 am |
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channels are numbered 0-12, so use
| Code: | set_adc_channel(0); //for AN0
set_adc_channel(1); //for AN1 |
instead PIN_A0, PIN_A1, these PIN_XX are defined to some higher values, you might have had luck, it got truncated to the lower bits, so this is not causing your problem.
If you get valid readings, but the values are floating, then try to increase the wait time in the delay_us to let thing settle.
It can be a hardware design problem also. Noise can cause these problems, is your VREFs of a proper impedance? (put capacitors on your Vrefs) What is the impedance of your analog signals? If you have a slow moving signal anyway, you can put a capacitor on your signal to filter noise.
To lessen digital noise in the PIC itself, you can also consider putting the PIC into sleep during conversion with (but you should have smoother readings without this sleep thing also)
| Code: | read_adc(ADC_START_ONLY);
sleep();
value=read_adc(ADC_READ_ONLY);
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