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deenadayalan
Joined: 19 Oct 2013
Posts: 19
Location: salam
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| pic18f4431 with adc |
 Posted: Wed Sep 10, 2014 11:28 pm |
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dear all, i am using pic18f4431 controller. I am using adc channel pin a0. I got 255 only in serial window through hardware crystal value 20mhz. Pls help me dear all
i initialized like
| Code: | void main()
{
unsigned int valadc=0;
set_tris_a(0x1f);
setup_adc_ports(sAN0|VSS_VDD);
setup_adc(ADC_CLOCK_INTERNAL|ADC_TAD_MUL_0|ADC_WHEN_INT0|ADC_INT_EVERY_OTHER);
setup_timer_0(RTCC_INTERNAL);
set_adc_channel(0);
while(true)
{
delay_ms(100);
valadc = read_adc();
valadc=valadc*0.0197;
printf("\n\r");
printf("%u",valadc);
}
}
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| Code: | /*************header file***************/
#include <18F4431.h>
#device adc=8
#FUSES NOWDT //No Watch Dog Timer
#FUSES WDT128 //Watch Dog Timer uses 1:128 Postscale
#FUSES HS //High speed Osc (> 4mhz)
#FUSES NOPROTECT //Code not protected from reading
#FUSES NOIESO //Internal External Switch Over mode disabled
#FUSES NOBROWNOUT //No brownout reset
#FUSES BORV27 //Brownout reset at 2.7V
#FUSES NOPUT //No Power Up Timer
#FUSES NOCPD //No EE protection
#FUSES STVREN //Stack full/underflow will cause reset
#FUSES NODEBUG //No Debug mode for ICD
#FUSES NOLVP //Low Voltage Programming on B3(PIC16) or B5(PIC18)
#FUSES NOWRT //Program memory not write protected
#FUSES NOWRTD //Data EEPROM not write protected
#FUSES FCMEN //Fail-safe clock monitor enabled
#FUSES NOWINEN //WDT Timer Window Disabled
#FUSES T1LOWPOWER //Timer1 low power operation when in sleep
#FUSES HPOL_HIGH //High-Side Transistors Polarity is Active-High (PWM 1,3,5 and 7)
//PWM module high side output pins have active high output polarity
#FUSES NOWRTC //configuration not registers write protected
#FUSES NOWRTB //Boot block not write protected
#FUSES NOEBTR //Memory not protected from table reads
#FUSES NOEBTRB //Boot block not protected from table reads
#FUSES NOCPB //No Boot Block code protection
#FUSES LPOL_HIGH //Low-Side Transistors Polarity is Active-High (PWM 0,2,4 and 6)
//PWM module low side output pins have active high output polar
#FUSES PWMPIN //PWM outputs disabled upon Reset
#FUSES MCLR //Master Clear pin enabled
#FUSES FLTAC1 //FLTA input is multiplexed with RC1
#FUSES SSP_RC //SCK/SCL=RC5, SDA/SDI=RC4, SDO=RC7
#FUSES PWM4B5 //PWM4 output is multiplexed on RB5
#FUSES EXCLKC3 //TMR0/T5CKI external clock input is muliplexed with RC3
#use delay(clock=20000000)
#use rs232(baud=9600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8) |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19539
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| Posted: Thu Sep 11, 2014 12:22 am |
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Three reasons one after the other:
adc=8
tells the compiler to only read the 8bit value from the adc....
Then:
unsigned int valadc=0;
How big is an int?.
Then:
printf("%u",valadc);
What size variables can %u handle?. Look at what %Lu handles instead.
Each of these will stop you getting the 10bit value. |
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deenadayalan
Joined: 19 Oct 2013
Posts: 19
Location: salam
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| Posted: Thu Sep 11, 2014 1:32 am |
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8 bit adc enough this application sir , i used int but simulation showed negative values ,if i use unsigned int and %u simulation showed 0 to 255
properly ,i checked in a0 pin during the adc input,voltage reaching in a0 but i got 255 only in output window
this is my problem sir |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19539
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| Posted: Thu Sep 11, 2014 1:45 am |
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Er....
An 8bit value, has 256 values. 0 to 255. 255, is the biggest value that the ADC can return in 8bit mode, and the biggest value that an int8 can hold. |
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deenadayalan
Joined: 19 Oct 2013
Posts: 19
Location: salam
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| Posted: Thu Sep 11, 2014 2:32 am |
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| even i am connecting adc to gnd result is 255 sir didn't show 0 |
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deenadayalan
Joined: 19 Oct 2013
Posts: 19
Location: salam
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| Posted: Thu Sep 11, 2014 2:38 am |
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this code also showed same result,result 03ff didnt change any analog input
| Code: | #include <18F4431.h>
#device adc=10
#fuses HS,NOWDT,NOPROTECT,BROWNOUT,PUT,NOLVP
#use delay(clock=20000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
//=================================
void main()
{
int16 result;
setup_adc_ports(sAN0);
setup_adc(ADC_CLOCK_DIV_32);
set_adc_channel(0);
delay_us(15);
while(1)
{
result = read_adc();
printf("%LX \n\r", result);
delay_ms(500);
}
} |
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rikotech8
Joined: 10 Dec 2011
Posts: 376
Location: Sofiq,Bulgariq
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| Posted: Thu Sep 11, 2014 2:39 am |
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Valadc = valadc * 0,0197
The right side of the equation returns a floating point since the 0,0197 is such format.
Then you asaign it to an unint. It is uncorrect.
_________________
A person who never made a mistake never tried anything new. |
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deenadayalan
Joined: 19 Oct 2013
Posts: 19
Location: salam
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| Posted: Thu Sep 11, 2014 2:45 am |
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| thank you dear rikotech8 , i am getting same problem another attached example. i couldnt find my mistake |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19539
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| Posted: Thu Sep 11, 2014 3:04 am |
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Well you are telling the ADC to sample on an interrupt....
Just look in the forum, at code people use for the ADC. Your setup, is _not_ how to use the adc.
An int, is unsigned by default.
What changes how it is displayed, is the format in the printf statement. %d, prints it as a signed value, %u prints it as an unsigned.
Your maths is completely screwed. The int, can't hold the result in any meaningful manner.....
| Code: |
void main()
{
int8 valadc;
setup_adc_ports(sAN0|VSS_VDD);
setup_adc(ADC_CLOCK_INTERNAL); //OK for 8bit, but not recommended
set_adc_channel(0); //voltage input on pin2.
while(true)
{
delay_ms(100);
valadc = read_adc();
valadc=(valadc * 10L) / 51; //at this point the multiply needs 16bit. 'L'
printf("\n\r%3.1w volts",valadc); //display as x.x volts
}
}
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As a general comment, add 'ERRORS' to your RS232 declaration.
ERRORS, is _required_ when using hardware RS232, unless _you_ handle the error conditions yourself. It is a problem waiting to catch you, unless you use it. |
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deenadayalan
Joined: 19 Oct 2013
Posts: 19
Location: salam
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| Posted: Thu Sep 11, 2014 3:35 am |
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| thank you dear Ttelmah i got continuously 5.0 volts, i used your code, again thank you for your valuable code, i used 20mhz crystal 22pf capacitor in my hardware circuit. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19539
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| Posted: Thu Sep 11, 2014 3:47 am |
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| Seriously I'd bet pin 2 is shorted high. |
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deenadayalan
Joined: 19 Oct 2013
Posts: 19
Location: salam
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| Posted: Thu Sep 11, 2014 4:01 am |
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sir i checked normally it has 0.8 v
when connected variable resistor for adc input
adc v --------------- controller pin (v)
starting -------------- 0.004
middle --------------- 2.505
ending ------------ 5 |
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deenadayalan
Joined: 19 Oct 2013
Posts: 19
Location: salam
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| Posted: Thu Sep 11, 2014 6:50 am |
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dear all i changed crystal value (16mhz) . i got perfect output thank you very much sir................  |
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