CCS/TMS320F2812: ADC not working on Channel B of TMS320F2812

Tool/software: Code Composer Studio

Helllo Experts,

I'm trying to run ADC code on TMS320F2812 using SYS/BIOS RTOS. i have all pins on channel A (8) ADC working (legacy code). i wanted to sample channel B (8 channels) as part of modifications.

I just made some basic changes to the code & observed that I'm getting expected voltage on ADCINB0 but incorrect values on the rest of channel B.

All the pins on ADCINB1-B7 are not connected to anything in schematic & I have confirmed on the board that the voltage measurement is about 0V. I am reading anywhere between 1.9V to 2.5V (depending on channels), consistently though. 

I have gone through the entire ADC module documentation of the uC (ADC_spru060d) but can't seem to understand what could be the issue, can anyone pleasee help me... the configuration of ADC is as below.

- dual sequencer

- start stop type

- sw controlled

code attached. 

AdcRegs.ADCTRL1.bit.SUSMOD    = 2u;   //Sequencer stops after current conversion
	AdcRegs.ADCTRL1.bit.ACQ_PS    = 0xfu; //16 cycles acquisition window 
 	AdcRegs.ADCTRL1.bit.CPS       = 1u;   //Divide the HSPCLK by 2
 	AdcRegs.ADCTRL1.bit.CONT_RUN  = 0u;   //Start Stop Mode
 	AdcRegs.ADCTRL1.bit.SEQ_OVRD  = 1u;   //Sequencer override enabled
 	AdcRegs.ADCTRL1.bit.SEQ_CASC  = 0u;   //Dual sequencer mode

 	//ADC CTRL3 Reg Initialization
 	AdcRegs.ADCTRL3.bit.ADCEXTREF = 1u;   //External reference enabled.
 	AdcRegs.ADCTRL3.bit.ADCCLKPS  = 0xfu; //Divide HSPCLK by 30

 	//ADCMAXCONV Reg Initialization
 	AdcRegs.ADCMAXCONV.bit.MAX_CONV1 = 0x7u; //8 conversion in channel A
 	AdcRegs.ADCMAXCONV.bit.MAX_CONV2 = 0x7u; //8 conversion in channel B


 	//ADC SEQ1 select register as per REV AD
 	AdcRegs.ADCCHSELSEQ1.bit.CONV00 = 0u; //ADCINA0	
	AdcRegs.ADCCHSELSEQ1.bit.CONV01 = 1u; //ADCINA1	
	AdcRegs.ADCCHSELSEQ1.bit.CONV02 = 2u; //ADCINA2	
	AdcRegs.ADCCHSELSEQ1.bit.CONV03 = 3u; //ADCINA3	

	//ADC SEQ2 select register
 	AdcRegs.ADCCHSELSEQ2.bit.CONV04 = 4u; //ADCINA4	
	AdcRegs.ADCCHSELSEQ2.bit.CONV05 = 5u; //ADCINA5	
	AdcRegs.ADCCHSELSEQ2.bit.CONV06 = 6u; //ADCINA6	
	AdcRegs.ADCCHSELSEQ2.bit.CONV07 = 7u; //ADCINA7	

	//ADC SEQ3 select register
 	AdcRegs.ADCCHSELSEQ3.bit.CONV08 = 8u;  //ADCINB0 
	AdcRegs.ADCCHSELSEQ3.bit.CONV09 = 9u;  //ADCINB1 
	AdcRegs.ADCCHSELSEQ3.bit.CONV10 = 10u; //ADCINB2 
	AdcRegs.ADCCHSELSEQ3.bit.CONV11 = 11u; //ADCINB3 

	//ADC SEQ4 select register
	AdcRegs.ADCCHSELSEQ4.bit.CONV12 = 12u; //ADCINB4 N/C
	AdcRegs.ADCCHSELSEQ4.bit.CONV13 = 13u; //ADCINB5 N/C
	AdcRegs.ADCCHSELSEQ4.bit.CONV14 = 14u; //ADCINB6 N/C
	AdcRegs.ADCCHSELSEQ4.bit.CONV15 = 15u; //ADCINB7 


	//Start Bandgap and reference circuitry. This is placed here to powerup ADC
	//after setting the registers.
	AdcRegs.ADCTRL3.bit.ADCBGRFDN = 3u;

	//7ms gap is required before ADC can be powered on. The below gap is about 10ms
	for(iVol= 0; iVol< ( (900000/2)/12 ); iVol++)
    {

    }

    AdcRegs.ADCTRL3.bit.ADCPWDN = 1u;

    //20 micro seconds required before conversion starts
   	for(iVol= 0; iVol< ( (1500/2)/12 ); iVol++)
    {

    }

//TRIGGER ADC

if( adc_channel == ADC_CHANNEL_A )
{
AdcRegs.ADCTRL2.bit.INT_ENA_SEQ1 = 1u;
AdcRegs.ADCTRL2.bit.SOC_SEQ1 = 1u;
}
else if( adc_channel == ADC_CHANNEL_B )
{
AdcRegs.ADCTRL2.bit.INT_ENA_SEQ2 = 1u;
AdcRegs.ADCTRL2.bit.SOC_SEQ2 = 1u;
}