General • Re: Default GPIO settings need to be spelled out, user will trip on seemingly simple things like a TSOP4838

Just trying to understand how useful is their 50-80K R(pu) R(pd) in the electricals. Assume I'm a little slow. If possible, someone explain to me what those figures are based on. Measured with what, at what voltage, or not measured, merely characterized.

I don't actually know but this is my guess. Say the pull-up and pull-down "resistors" are actually mosfets, since mosfets take up much less area than proper resistors, the IV curve might look something like this:When conducting in a digital circuit, the voltage across an internal pull-up or pull-down is likely close to IOVDD, which could range from 1.8V to 3.3V, depending on the logic levels used. I plotted diagonal straight lines, the gradient of which could be expressed as a resistance.

I suppose there might also be variance because of tolerance and temperature sensitivity and other factors.

There are different ways of making "resistors" in CMOS, both things that reasonably follow Ohm's law and pull-ups and pull-downs that don't but suffice for digital circuits. I don't know what type was used for RP2040.

Statistics: Posted by alastairpatrick — Wed Apr 10, 2024 10:14 pm

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