fruit-bat

Well, if the 0.8 to 2.0 volts thing is correct, at least 1.2v.I I don't think it matters if it is inverting or not. Thanks for the links I will...

I've done some more reading and found the rp2040 inputs have their own hysteresis... https://raspberrypi.github.io/pico-sdk-doxygen/group__hardware__gpio.html#ga1f52eecc12d4348ef8bd1e17bdb4b107 I probably need to find out more about that.

Been reading this... https://en.m.wikipedia.org/wiki/Line_level ... which suggests 10k (rather than the 1k) load resistance. Perhaps that would give a bit more of a voltage swing.

They are easy to make with an op amp. I've ordered some that will run at 3v to have a play with. We can compare notes then 🙂. I'll post...

This site is good... https://www.random-science-tools.com/electronics/inverting-schmitt-trigger-calculator.htm

Something like this...  The pot is there to adjust the threshold, which we could fix if we find a good value. I'm not sure about the lm224n, just...

...but it does turn out the op-amps I have ordered are going to take a long time to get to me!

Hi, sorry for the slow reply, 'real-life' has been distracting me! The 1st circuit looks like a non-inverting comparator, without hysteresis. I like the way the bias is arranged; the...

Thanks for finding those... I will get back to this at some point!

I've added a little test program which reads GP11 at 44Khz and sends 1s and 0s to the USB uart. Not as good as a dual-channel scope but it's something!...