CC3220SF-LAUNCHXL: ADC module of CC3220SF

Hi,

I am trying to use the 4 ADC channels that on the CC3220SF Board. I ran the adcsinglechannel sample code. I am able to read changes in voltages but the value is not correct. 

This is the code segment in my project regarding this issue.

 ADC_init();

ADC_Params_init(&params);
adc = ADC_open(Board_ADC1, &params);
/* Blocking mode conversion */
res = ADC_convert(adc, &adcValue0);

if (res == ADC_STATUS_SUCCESS)
{
adcValue0MicroVolt = ADC_convertRawToMicroVolts(adc, adcValue0);
}

ADC_close(adc);

When the input is 2.2Vs, ADC_convertRawToMicroVolts is outputting 1064694 (1.06V)

For 3.3V I am getting 1389978 and for 5V I am getting 1467000. (For the 3.3V and the 5V inputs, I use the board voltages).

Is there a step I am missing in the configuration or a calibration step I am missing?

Thank you