ADC reading drift error

Official Hardware Mega GIGA R1 WiFi
1

Hi guys,
I’m facing a problem with the Giga when I’m trying to sweep the DAC voltage from 0-1.7V, the ADC1,2 reading drifts slightly while it’s supposed to be constant. I’m using advanced analog library for fast 16bit ADCs and analogWrite for DAC. Here’s a graph:

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Blue DAC output goes through a gain amplifier –> sma before oscilloscope, hence it ranges from 0 to 12V.
Do you guys think this is a mixed signal issue of the Giga hardware itself? Do you guys have any ideas of fixing this type of issue?
(This drift appears in my Serial Monitor, but not on the ADC pin itself. So, I’m certain that it’s the problem inside Giga, not my signal or PCB)

2

How are you using a separate meter to confirm a steady voltage? You need to do that if you want to debug the problem.

3

Are you sure the Giga's A/D is suitable for voltage measurements.
I think default Aref on a Giga is VCC, which is only good for ratiometric measurements.
Leo..

4

Start with an annotated schematic. The drift can come from several sources. Did you confirm your reference voltages were stable during this testing.