> The RP2040 ADC does not have an on-board reference and therefore uses its own power supply as a reference. On Pico the ADC_AVDD pin (the ADC supply) is generated from the SMPS 3.3V by using an R-C filter (201 ohms into 2.2μF)
Which doesn't sound promising and I don't see a DAC in the RP2040 datasheet.
It's good and bad. Nice that they've filtered AVCC pretty heavily-- 360Hz corner frequency-- lots of microcontroller boards don't.
Less nice that the ADC scale will be affected by power supply offset, though that all depends upon how "good" the board 3V3 is. The bandgap and error amplifier on the DC-DC converter IC is good at least-- max +/- 1%.
Comments
Thanks for this summary.
I am excited about the DMA and PIOs having used BeagleBoard PRUs, but what about the quality of the ADCs/DACs?
Isn't all the talk of hard real-time applications and so on somewhat moot if those aren't high quality enough?
(afraid I haven't had time to read the datasheet yet!)
From the devboard datasheet:
> The RP2040 ADC does not have an on-board reference and therefore uses its own power supply as a reference. On Pico the ADC_AVDD pin (the ADC supply) is generated from the SMPS 3.3V by using an R-C filter (201 ohms into 2.2μF)
Which doesn't sound promising and I don't see a DAC in the RP2040 datasheet.
It's good and bad. Nice that they've filtered AVCC pretty heavily-- 360Hz corner frequency-- lots of microcontroller boards don't.
Less nice that the ADC scale will be affected by power supply offset, though that all depends upon how "good" the board 3V3 is. The bandgap and error amplifier on the DC-DC converter IC is good at least-- max +/- 1%.
Right. I wonder if the Arduino version will be better for this, or whether we might need to wait for future boards from RPi.