CCS/TMS320F28069: ADC issues

Tool/software: Code Composer Studio

I am trying to understand how to configure ADC in F28069. I used the example adc program (as it is) in the controlsuite and connected a power supply to ADCINA2 pin. But when I read the results, I am getting 1480 for 3.3V whereas it should be 4095. Can someone please explain what might be the issue? below is the program I used.

//###########################################################################
// Description:
//! \addtogroup f2806x_example_list
//! <h1> ADC Start of Conversion (adc_soc)</h1>
//!
//! This ADC example uses ePWM1 to generate a periodic ADC SOC - ADCINT1.
//! Two channels are converted, ADCINA4 and ADCINA2.
//!
//! \b Watch \b Variables \n
//! - Voltage1[10]    - Last 10 ADCRESULT0 values
//! - Voltage2[10]    - Last 10 ADCRESULT1 values
//! - ConversionCount - Current result number 0-9
//! - LoopCount       - Idle loop counter
//
//
//###########################################################################
// $TI Release: F2806x C/C++ Header Files and Peripheral Examples V151 $
// $Release Date: February  2, 2016 $
// $Copyright: Copyright (C) 2011-2016 Texas Instruments Incorporated -
//             http://www.ti.com/ ALL RIGHTS RESERVED $
//###########################################################################

#include "DSP28x_Project.h"     // Device Headerfile and Examples Include File

// Prototype statements for functions found within this file.
__interrupt void adc_isr(void);
void Adc_Config(void);

// Global variables used in this example:
Uint16 LoopCount;
Uint16 ConversionCount;
Uint16 Voltage1[10];
Uint16 Voltage2[10];

main()
{

// Step 1. Initialize System Control:
// PLL, WatchDog, enable Peripheral Clocks
// This example function is found in the F2806x_SysCtrl.c file.
   InitSysCtrl();

// Step 2. Initialize GPIO:
// This example function is found in the F2806x_Gpio.c file and
// illustrates how to set the GPIO to it's default state.
// InitGpio();  // Skipped for this example

// Step 3. Clear all interrupts and initialize PIE vector table:
// Disable CPU interrupts
   DINT;

// Initialize the PIE control registers to their default state.
// The default state is all PIE interrupts disabled and flags
// are cleared.
// This function is found in the F2806x_PieCtrl.c file.
   InitPieCtrl();

// Disable CPU interrupts and clear all CPU interrupt flags:
   IER = 0x0000;
   IFR = 0x0000;

// Initialize the PIE vector table with pointers to the shell Interrupt
// Service Routines (ISR).
// This will populate the entire table, even if the interrupt
// is not used in this example.  This is useful for debug purposes.
// The shell ISR routines are found in F2806x_DefaultIsr.c.
// This function is found in F2806x_PieVect.c.
   InitPieVectTable();

// Interrupts that are used in this example are re-mapped to
// ISR functions found within this file.
   EALLOW;  // This is needed to write to EALLOW protected register
   PieVectTable.ADCINT1 = &adc_isr;
   EDIS;    // This is needed to disable write to EALLOW protected registers

// Step 4. Initialize all the Device Peripherals:
// This function is found in F2806x_InitPeripherals.c
// InitPeripherals(); // Not required for this example
   InitAdc();  // For this example, init the ADC
   AdcOffsetSelfCal();

// Step 5. User specific code, enable interrupts:

// Enable ADCINT1 in PIE
   PieCtrlRegs.PIEIER1.bit.INTx1 = 1; // Enable INT 1.1 in the PIE
   IER |= M_INT1;       // Enable CPU Interrupt 1
   EINT;                // Enable Global interrupt INTM
   ERTM;                // Enable Global realtime interrupt DBGM

   LoopCount = 0;
   ConversionCount = 0;

// Configure ADC
 EALLOW;
    AdcRegs.ADCCTL2.bit.ADCNONOVERLAP = 1; // Enable non-overlap mode
 AdcRegs.ADCCTL1.bit.INTPULSEPOS = 1; // ADCINT1 trips after AdcResults latch
 AdcRegs.INTSEL1N2.bit.INT1E     = 1; // Enabled ADCINT1
 AdcRegs.INTSEL1N2.bit.INT1CONT  = 0; // Disable ADCINT1 Continuous mode
    AdcRegs.INTSEL1N2.bit.INT1SEL  = 1;    // setup EOC1 to trigger ADCINT1 to fire
    AdcRegs.ADCSOC0CTL.bit.CHSEL  = 4;    // set SOC0 channel select to ADCINA4
    AdcRegs.ADCSOC1CTL.bit.CHSEL  = 2;    // set SOC1 channel select to ADCINA2
    AdcRegs.ADCSOC0CTL.bit.TRIGSEL  = 5;    // set SOC0 start trigger on EPWM1A, due to round-robin SOC0 converts first then SOC1
    AdcRegs.ADCSOC1CTL.bit.TRIGSEL  = 5;    // set SOC1 start trigger on EPWM1A, due to round-robin SOC0 converts first then SOC1
 AdcRegs.ADCSOC0CTL.bit.ACQPS  = 6; // set SOC0 S/H Window to 7 ADC Clock Cycles, (6 ACQPS plus 1)
 AdcRegs.ADCSOC1CTL.bit.ACQPS  = 6; // set SOC1 S/H Window to 7 ADC Clock Cycles, (6 ACQPS plus 1)
 EDIS;

// Assumes ePWM1 clock is already enabled in InitSysCtrl();
   EPwm1Regs.ETSEL.bit.SOCAEN = 1;  // Enable SOC on A group
   EPwm1Regs.ETSEL.bit.SOCASEL = 4;  // Select SOC from CMPA on upcount
   EPwm1Regs.ETPS.bit.SOCAPRD  = 1;  // Generate pulse on 1st event
   EPwm1Regs.CMPA.half.CMPA  = 0x0080; // Set compare A value
   EPwm1Regs.TBPRD     = 800; // Set period for ePWM1
   EPwm1Regs.TBCTL.bit.CTRMODE  = 0;  // count up and start

// Wait for ADC interrupt
   for(;;)
   {
      LoopCount++;
   }

}

__interrupt void  adc_isr(void)
{

  Voltage1[ConversionCount] = AdcResult.ADCRESULT0;
  Voltage2[ConversionCount] = AdcResult.ADCRESULT1;

  // If 20 conversions have been logged, start over
  if(ConversionCount == 9)
  {
     ConversionCount = 0;
  }
  else ConversionCount++;

  AdcRegs.ADCINTFLGCLR.bit.ADCINT1 = 1;  //Clear ADCINT1 flag reinitialize for next SOC
  PieCtrlRegs.PIEACK.all = PIEACK_GROUP1;   // Acknowledge interrupt to PIE

  return;
}