cc2538 ADC problem

Other Parts Discussed in Thread: CC2538

Hi everyone,

 I am integrating battery monitoring section in  my code. Here i am facing some issue in ADC conversion.

Power supply is 3.3v.

I am using SmartRf06 EV board with cc2538.

For adc, the channel i am using is PA2 and internal reference voltage.

The ref voltage pin(33rd pin ,36rd pin .39...) in smartrf06 is connected to vdd, which is 2.3v as i measured.

Also R_Bias pin(42th pin) is 1.3 v.

How to select the internal reference voltage to a particular value?

My problem is , the ADC is converting values from 0 to 1.15 only. Above this all conversions are same.

In datasheet it is specified VDD5, which pin is vdd5 of cc2538?

The readings are,

For 0.28v   - 17292

      0.64v   - 25204

      0.95v   - 29996 

      1.11v   - 30252

      1.50v   - 32764

      ~

      2.00v   - 32764

      ~

      3.30v   - 32764

My code is,

SOCADCSingleConfigure(SOCADC_12_BIT,SOCADC_REF_INTERNAL);


while(1)
{
uint8_t dummySwPressed = ReadSwitchPressed();

if(dummySwPressed & SW_RIGHT)
{
SOCADCSingleStart(SOCADC_AIN2);

while(!SOCADCEndOfCOnversionGet());

Adcval = SOCADCDataGet();

sprintf(AdcvlaBuff,"%d",Adcval);

WriteStrToUART(AdcvlaBuff);
}

}

Thanks in advance,

jose