Please Help Me Understand SAR ADC | Cypress Semiconductor
Please Help Me Understand SAR ADC
This is actually related to my thread Noisy Differential Preamp into SAR ADC, but it is a somewhat different subject, so I'm starting a new topic.
I have made some progress on the noise but am still working on it. While I wait for precision resistors and a few other components to arrive tomorrow, hopefully, I've started looking deeper into the SAR ADC.
Using ADC_StartConvert(); and the EOC ISR, I have the conversions runnig in sync with the switching polarity of the excitation pins of the load sensor, as verfied by the debugger. I realize, however, that I don't understand what the results mean. I guess I'm still thinking in old-fashioned ADC terms in that I expect values between 0 and 4095 from a 12 bit ADC, but even on individual calls of GetResult16, I'm seeing values well beyond that. I've read the parts of the data sheet related to signed values, left vs right justification, but it hasn't become clear yet.
I'm confusing things by trying to gain a few bits more resolution by averaging over 256 samples called within the firmware. I wonder if that somehow clashing with or amplifying what is happening in the ADCs own "Samples averaged" settings. Again, reading that section of the datasheet has not yet clarified things for me.
This turning into another of my "too-uninformed-to-even-state-my-question-clearly" posts, but you all have provided useful information in response to them in the past. Hopefully I will someday be able to return the favor.