Ah. It seems the internal filter of the ADC is preventing me from subsampling.
Is there any way to switch off the internal filters of the Delta Sigma ADC?
(Time critical solution needed)
Can you provide some more information about your input signal. You said its 1.5 Volts peak to peak? that means if you add a 1.5 Volts offset, the signal will vary between 0.75 Volts and 2.25 Volts.
Also how have configured the ADC, which mode. How are you reading the values from ADC.
I don't believe that you cannot use the Sigma-Delta converter to sub-sample. The principle of operation is to highly oversample the input and then use dynamic correction and digital filters to reduce to the final sample rate. For your application, you may be better off with the PSoC5. It has a SAR ADC, where the sub-sampling should work just fine. Alternatively, you can use the mixers.
Try the new Kit-050 for analog designs.