I'm glad that you were able to figure it out.
The strange thing is that both of my Pi4 are faster on the USB transfer than my Pi5.
Two things that you should check nn the Pico.
1 - The Vref of the pico is from the 3.3V supply filter by a resistor and a capacitor. It is noisy and it could be not exactly 3.3V. If you want better performance use a shunt precision voltage reference like the LM4040 (Pico datasheet page 18).
2- Input impedance play a role on the input signal. What was to output impedance of your signal. The ADC Input impedance is around 100K ohm.
From Vout = Vin *(R1/R1+R2)
It looks like that your output impedance is around
1.9V = 2.3V * 100K / Rout + 100K => Rout = ~20K
The strange thing is that both of my Pi4 are faster on the USB transfer than my Pi5.
Two things that you should check nn the Pico.
1 - The Vref of the pico is from the 3.3V supply filter by a resistor and a capacitor. It is noisy and it could be not exactly 3.3V. If you want better performance use a shunt precision voltage reference like the LM4040 (Pico datasheet page 18).
2- Input impedance play a role on the input signal. What was to output impedance of your signal. The ADC Input impedance is around 100K ohm.
From Vout = Vin *(R1/R1+R2)
It looks like that your output impedance is around
1.9V = 2.3V * 100K / Rout + 100K => Rout = ~20K
Statistics: Posted by danjperron — Tue Feb 27, 2024 2:15 pm