dlloyd:
This really has me curious and willing to do a similar test with the Arduino Due, where I would generate the signal through DAC0 and connect this to the A0 input. Since this signal would be both generated and measured by using the same clock source, I could test the condition where the sampling frequency is in the same domain and is a multiple or at the same input frequency.I could try a 60-point sine wave table to generate a 60-Hz sine wave on DAC0 and measure each cycle with 60 samples (3600 samples per second). The purpose would be to measure the effect of oversampling with respect to each sample point on a sine wave. These sample points will not travel along the waveform (they'll always be at the same point in time).
I won't get the chance to do this for a few weeks and really can't make any promises ... I'll re-check this thread when I get back.
Anyone interested in doing a "synchronized" test, where everything originates from the same clock?
This is where I suspect the resolution improvement will be limited to the DAC bit resolution (12-bit max in this case).
I am interested in your proposed tests, dlloyd, for sure. Meanwhile, I think I may be able to recruit Hackscribble to do some testing, too, with his Arduino and a separate MCP4725 12-bit DAC, such as this: MCP4725 Breakout Board - 12-Bit DAC with I2C Interface [STEMMA QT / qwiic] : ID 935 : Adafruit Industries, Unique & fun DIY electronics and kits. This should demonstrate the viability and limitations of my library nicely (though not to the very high precision levels, of course, since it's only a 12-bit DAC), and I'll submit some suggested testing methods shortly. Since this DAC is stand-alone, it should be using a separate clock and be good to go.