This is true, but if using external multiplexing then there is a performance advantage to using more than one of the inputs for the reasons I outlined above:The RP2040 chip in a pico has one ADC. The four ADC input pins go through an internal mux to that single ADC. Only 3 are available on a pico.
- Maximum sample rate is only achievable in continuous mode: single input or automated round-robin of multiple of the chip inputs.
- Continuous sampling of a single input gives you no identifiable 'dead time' during which the external mux can be switched and the input settle. Probably there is in fact some dead time (the single ADC has a sample-and-hold), but there's no means to synchronize with it, and the duration is probably not long enough for the new input voltage to settle.
- Using multiple inputs, you can switch and settle external multiplexing on one input pin while the ADC is sampling on another input pin. Using a single pin you would need to wait for a sample to complete, switch the multiplexing, wait for a settling delay, then manually trigger the next sample: this would at best give half of the sample rate compared to continuous operation.
Statistics: Posted by arg001 — Thu Apr 04, 2024 9:03 am