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amcasi
Joined: 19 Jun 2015
Posts: 21
Location: Banned - Spammer
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| Please help. I do not read 18F4520 ADC correctly. |
 Posted: Sat Apr 07, 2018 2:32 am |
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Hi All
I am writing a program about reading pic18f4520 ADC and display it 7 segment display. Program is doing wrong reading from ADC. and then continue. I have trouble with this. program is below.
anybody help me for solution.
thanks.
| Code: |
#include <18f4520.h>
#device ADC=10 //ICD=TRUE
#include <c:\inc\defs_4520.h>
#FUSES INTRC_IO,NOFCMEN,PUT,NOCPB
//#FUSES NOPROTECT,NOWDT,MCLR,NOCPD,NOBROWNOUT,NOWRTC,NOWRTB,NOWRTD,NOEBTR,NOEBTRB
#use delay(CLOCK=8000000)
#use rs232(baud=9600, xmit=PIN_C6,rcv=PIN_C7)
void main(){
delay_ms(300);
set_tris_a(0x01);
set_tris_b(0x40);
set_tris_c(0x00);
set_tris_d(0x00);
set_tris_e(0x00);
output_a(0x01);
output_b(0x40);
output_c(0x00);
output_d(0x00);
output_e(0x00);
setup_adc_ports(AN0|VSS_VDD);
setup_timer_0(T0_INTERNAL|T0_8_BIT|T0_DIV_256);
setup_adc(ADC_CLOCK_INTERNAL);
set_adc_channel(0);
enable_interrupts(INT_TIMER0);
enable_interrupts(GLOBAL);
while (true){
DAC = read_adc();
delay_us(30);
//DAC=(DAC/1024)*5;
printf("A/D value = %3lu", DAC);
printf("\n\r");
delay_ms(100);
}
} |
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temtronic
Joined: 01 Jul 2010
Posts: 9093
Location: Greensville,Ontario
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| Posted: Sat Apr 07, 2018 5:36 am |
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I didn't look at all the code as
this line...
setup_adc(ADC_CLOCK_INTERNAL);
is incorrect.
Typically the ..internal option is used when the PIC reads the ADC while asleep.
There is a table ( 19-1) which shows what are valid ADC clock setups for PIC clock speeds. There are 2 options for you for <-8MHz. which is best for you ,depends on how you need to use the ADC. I'd choose one option, run say 1000 sample, then choose the other option, run 1000 samples again. Compare the results to what you expect and choose the option that gives the best results.
Now there may be other code wrong but this one is the FIRST I would correct as according to the datasheet,using ...internal WILL give 'bad numbers'.
Jay |
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amcasi
Joined: 19 Jun 2015
Posts: 21
Location: Banned - Spammer
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| Posted: Sat Apr 07, 2018 7:21 am |
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in 18f4520.h file there are these constants.
| Code: |
// Constants used for SETUP_ADC() are:
#define ADC_OFF 0 // ADC Off
#define ADC_CLOCK_DIV_2 0x100
#define ADC_CLOCK_DIV_4 0x04
#define ADC_CLOCK_DIV_8 0x01
#define ADC_CLOCK_DIV_16 0x05
#define ADC_CLOCK_DIV_32 0x02
#define ADC_CLOCK_DIV_64 0x06
#define ADC_CLOCK_INTERNAL 0x07 // Internal 2-6us
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Regards |
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temtronic
Joined: 01 Jul 2010
Posts: 9093
Location: Greensville,Ontario
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| Posted: Sat Apr 07, 2018 8:02 am |
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| Please note that just because they are listed does not mean you can use them without reading the ADC section of the PIC's datasheet. There are specific rules that must followed to properly use the PIC's ADC subsection. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Re: Please help. I do not read 18F4520 ADC correctly. |
| Posted: Sat Apr 07, 2018 9:23 am |
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| amcasi wrote: | Hi All
void main(){
delay_ms(300);
set_tris_a(0x01);
set_tris_b(0x40);
set_tris_c(0x00);
set_tris_d(0x00);
set_tris_e(0x00);
output_a(0x01);
output_b(0x40);
output_c(0x00);
output_d(0x00);
output_e(0x00);
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The line in bold above is over-writing the TRIS for PortA. That line makes
PortA into all output pins. Look at the .LST file. It's setting TRISA = 0x00.
| Quote: | ..... output_a(0x01);
015A: CLRF TRISA
015C: MOVLW 01
015E: MOVWF LATA |
The A/D conversion on pin A0 requires that it must be set as an input pin.
So this is the problem that must be fixed.
Since you are setting the TRIS for all ports with set_tris_x() statements,
it would be best if you switch the compiler to fast_io mode for all i/o ports.
Add the statement shown in bold below, in that exact location:
| Quote: | #include <18f4520.h>
#device ADC=10
#FUSES INTRC_IO,NOFCMEN,PUT,NOCPB
#use delay(CLOCK=8000000)
#use fast_io(all)
#use rs232(baud=9600, xmit=PIN_C6,rcv=PIN_C7) |
Now when you do output_a(), it doesn't over-ride your TRISA settings.
It only writes to the latch for PortA. This is what you want.
Look at the .LST file to see this:
| Quote: | ..... output_a(0x01);
015A: MOVLW 01
015C: MOVWF LATA |
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amcasi
Joined: 19 Jun 2015
Posts: 21
Location: Banned - Spammer
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| Problem Solved |
| Posted: Tue Apr 10, 2018 2:03 am |
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Thanks friend,
I solved problem. There is short circuit Pin_A0 and PIN_A1. I corrected and it works. I have a one A/D input, others and Digital out. Problem was there.
Thanks for everybody.
Huseyin |
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