Serial Comm using AT89C51 and ADC0832

hello Everyone..
there is my code for interfacing ADC0832 and AT89C51..

#include<reg52.h>
#include<stdio.h>

sbit ADC_CS = P2^0;
sbit ADC_CLK = P2^1;
sbit ADC_DO = P2^2;
sbit ADC_DI = P2^3;


void InitSerial(void);
void write_adc_byte(char data_byte);
char ReadADC(unsigned char channel);
void DelayMs(unsigned int count);



//---------------------------------------
// Main program
//---------------------------------------
void main(void)
{
InitSerial(); // Initialize serial port
while(1)
{
putchar(0x0C); // clear Hyper terminal
printf("Ch 0 : %bu\n\r",ReadADC(0));
printf("Ch 1 : %bu\n\r",ReadADC(1));
DelayMs(100); // Delay about 100 mS
}
}

//---------------------------------------
// Initialize serial port
//---------------------------------------
void InitSerial(void)
{
SCON = 0x52; // setup serial port control
TMOD = 0x20; // hardware (9600 BAUD @11.05592MHZ)
TH1 = 0xFD; // TH1
TR1 = 1; // Timer 1 on
}


//---------------------------------------
// read analog from ADC
// Single end mode(2 channel)
//---------------------------------------
char ReadADC(unsigned char channel)
{
unsigned char i,k;
unsigned char AdcResult; // 8 bit

ADC_CS=0; // Active chip select
k++; // Delay about 1us
ADC_CLK=0; // make clock low first
k++;k++;
channel = channel? 0xE0 : 0xC0;
k++; // delay about 1us
//--- write command 3 bit ----------
for(i=0; i< 3;i++) {
ADC_DI = (channel & 0x80) != 0;
channel<<=1;
ADC_CLK=1;
k++;k++; // delay about 1us
ADC_CLK=0;
}

//--- read ADC result 8 bit --------
AdcResult=0;
for(i=0;i<8;i++) {
ADC_CLK=1;
k++; // delay about 1us
ADC_CLK=0;
k++; // delay about 1us
AdcResult<<=1;
AdcResult=AdcResult | (ADC_DO & 0x01);
ADC_CLK=1;
k++; // delay about 1us
ADC_CLK=0;
k++; // delay about 1us
}
ADC_CS=1;
return(AdcResult);
}

//---------------------------------------
// Delay mS function
//---------------------------------------

void DelayMs(unsigned int count) { // mSec Delay 11.0592 Mhz
unsigned int i; // Keil v7.5a
while(count) {
i = 115;
while(i>0) i--;
count--;
}

}
this code shows output
ch 0 : 255
ch 1 : 255
Even when I am changing voltages at input of ch0 and ch1... why..?