ADC 输入0v结果寄存器不为0

只看该作者 · 2014-5-14 21:15

给AD口输入0v电压，但经过AD转换后，结果寄存器的值160 左右，不为0，请各位指教：具体程序如下：
static void Adc_init(void)
{
ADCON1bits.ADCS = 0b010;//AD conveter clock choose
//TRISAbits.TRISA3 = 1; //Set the port A3 as Input
TRISB0 = 1; //Set as input
ANSB0 =1; // Set as analog input

ADCON1bits.ADPREF = 0b00; //reference votage choose

ADCON1bits.ADFM =1;//output right allain

}

Uint ADkey(void)
{
ADCON0bits.CHS = 0b01100; //AD channel choose
Uint ADC_Result = 0;
ADCON0bits.ADON =1; //enable AD convertion

Delay(20);

ADCON0bits.GO_nDONE =1; //start the ADC
while(ADCON0bits.GO_nDONE == 1);
ADC_Result = ADRES0L; //get the low result;
ADC_Result = ADRES0L + (ADRES0H<<6)*4; //get the result
return (ADC_Result);

}