An archive of community.esquilo.io as of Saturday January 26, 2019.

ADC Reference Selection

hexamer

First, let me say that I really like the idea behind your product - many good design decisions. It seems almost ideal for my project, so I plan to buy one soon.

As far as I can tell in looking at the schematic and library info the only ADC reference possible is the internal band-gap. Am I correct?

I need to take a measurement that is ratiometric, so it would be better to have an external ref derived from the sensor supply. I suppose I could use the internal reference to measure both supply and sensor, but would prefer otherwise since that would introduce another source of drift in the measurement.

Scott_Shumate

The ADC can be referenced to either the VREFH pin or the 1.2V band-gap reference. Esquilo Air is shipped with the VREFH pin tied to 3.3V via a ferrite bead (L2). This was done because there is no internal way to select a 3.3V reference and most users will expect the ADC to operate that way. If you want an external ADC reference on VREFH, you can remove L2 and supply the reference via the AREF pin on the Arduino headers. The AREF pin is tied directly to the VREFH.

We don't currently support selecting the band-gap reference for the ADC in the Squirrel API but it would be easy to add if you need it.

hexamer

Ahh, thank you. I should have inspected the schematic more closely :slight_smile: I will just depop L2