TM4C123GH6PM: TM4C123 ADC wrong value

Hi, It 's me again.

I am trying to read ADC value on TIVA. The value displayed in VOM is 3V, but ADC on TIVA returned 3731, which means 3731 * (3/4096)=2.7 V. 

I have tried with ADC0 and ADC1 too, but it still displays wrong value.

Here is my simple code: 

#include <stdint.h>
#include <stdbool.h>
#include "inc/hw_memmap.h"
#include "inc/hw_types.h"
#include "driverlib/debug.h"
#include "driverlib/sysctl.h"
#include "driverlib/adc.h"
#include "driverlib/timer.h"
#include "driverlib/gpio.h"
volatile uint32_t ui32Avg;

int main(void)
{
uint32_t ui32ADC0Value[4];

SysCtlClockSet(SYSCTL_SYSDIV_5|SYSCTL_USE_PLL|SYSCTL_OSC_MAIN|SYSCTL_XTAL_16MHZ);
SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC1);
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOE);
GPIOPinTypeADC(GPIO_PORTE_BASE, GPIO_PIN_0);
ADCSequenceConfigure(ADC1_BASE, 1, ADC_TRIGGER_PROCESSOR, 0);
ADCSequenceStepConfigure(ADC1_BASE, 1, 0, ADC_CTL_CH3);
ADCSequenceStepConfigure(ADC1_BASE, 1, 1, ADC_CTL_CH3);
ADCSequenceStepConfigure(ADC1_BASE, 1, 2, ADC_CTL_CH3);
ADCSequenceStepConfigure(ADC1_BASE, 1, 3, ADC_CTL_CH3|ADC_CTL_IE|ADC_CTL_END);
ADCSequenceEnable(ADC1_BASE, 1);

//TimerLoadSet(TIMER0_BASE, TIMER_BOTH,1000);
//TimerControlTrigger(TIMER0_BASE, TIMER_BOTH,true);
//TimerEnable(TIMER0_BASE, TIMER_BOTH);
while(1)
{
ADCIntClear(ADC1_BASE, 1);
ADCProcessorTrigger(ADC1_BASE, 1);
while(!ADCIntStatus(ADC1_BASE, 1, false))
{}
ADCSequenceDataGet(ADC1_BASE, 1, ui32ADC0Value);
ui32Avg = (ui32ADC0Value[0] + ui32ADC0Value[1] + ui32ADC0Value[2] + ui32ADC0Value[3])/4;

}
}