giúp em về ADC cu pic8f4431

[phamvanduan]

em viết thử ADC ma sao chay không dúng.dù thay đổi điện áp vào chân AN0 như thế nào thi adc vẫn đọc duy nhất 1 giá trị.cụ thể trong code là chỉ có led0 sáng.
thanks mọi người

#include <18F4431.h>
#device adc=10

#FUSES NOWDT //No Watch Dog Timer
#FUSES WDT128 //Watch Dog Timer uses 1:128 Postscale
#FUSES HS //High speed Osc (> 4mhz for PCM/PCH) (>10mhz for PCD)
#FUSES NOPROTECT //Code not protected from reading
#FUSES IESO //Internal External Switch Over mode enabled
#FUSES BROWNOUT //Reset when brownout detected
#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 LVP //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)
#byte PORTA = 0xF80
#byte PORTB = 0xF81
#byte PORTC = 0xF82
#byte PORTD = 0xF83
#byte PORTE = 0xF84
#bit led0 = PORTD.0
#bit led1 = PORTD.1
#bit led2 = PORTD.2
#bit led3 = PORTD.3
#bit led4 = PORTD.4

void main()
{
int done;
int16 adc;
set_tris_A(0xff);
set_tris_D(0x00);
setup_timer_0(RTCC_INTERNAL);
setup_timer_1(T1_INTERNAL|T1_DIV_BY_1);
setup_timer_2(T2_DISABLED,0,1);
setup_adc_ports(ALL_ANALOG);
setup_adc(ADC_CLOCK_INTERNAL);
while(true)
{
set_adc_channel(sAN0);
delay_ms(10);
adc = read_adc();
delay_us(100);
if(adc<400) led0=1;
else led1=1;

}

}