Right! I measured those voltages with the resistors connected to the Core.
I measured the resistor values with the resistors disconnected from the Core.
Forgot that part Very tired today… was up til 1am working on my WebServer port and got it working…
FWIW: The 1st reading from the ADC is always low because it’s sets up the ADC that first time through… and something something… I dunno. It’s just always low.
I calculated the expected value based on the resistors and the 3V3* voltage, not the measured 2.8110V on the input.
So it seems like the ADC is correct in both cases, it’s just lowering the voltage at the input somehow.
So I measured the A6 voltage with respect to GND with the Tinker app from the Sparkulator still installed… this is going to blow your mind…
Right after reset the input measures: 2.9683V
After the first reading the input meas: 2.8820V
Before the first reading the pin is set up as open (tri-state). So it makes sense that the voltage is closest to ideal (which is 2.9731V)
After that first reading it’s set as an ADC input… and puts a load on the resistors even when not performing a conversion. I guess I should have expected this… and it’s interesting to keep this in mind.
Why the local master puts more load on the resistors than the sparkulator is beyond me though…