Spent the weekend making my plant talk to me, sort of

I did almost the same thing with a basil pot on the kitchen windowsill last winter, except mine runs off a spare board from an old weather station project and the face is drawn on a tiny OLED instead of a round screen. The basil is dead now, not going to pretend otherwise, but the face part survived and got moved onto a pothos that seems nearly impossible to kill.

My version of your flickering problem was the screen going half white every few seconds. Turned out I was redrawing the whole display every pass through the loop, even when nothing changed. Once I added a check to only redraw when the mood actually switched, it stopped acting up. Maybe simpler than your two-task split but it got me there.

On the sensor, I never got the calibration right the first time. My dry reading was taken right after repotting, when the soil was loose and fluffy, so the numbers drifted once it settled and compacted. Second attempt I waited a few days after repotting before taking the baseline and it's held steady since.

Also can confirm the kid thing. Mine feeds the pothos without being asked now, which is more than I can say for taking out the recycling.

Funny timing reading this, I've been going the opposite direction with my setup, stripping things down instead of adding. I had a little e-paper display on a fern for a while and honestly got tired of it. The battery kept dying, and every time I repotted the plant I'd break a wire. Now the same readings just drive three little lights on the shelf bracket underneath. Green means fine, yellow means check this weekend, red means water today. My wife understands it instantly and I don't charge anything for months at a time.

One thing I'd flag from my own trial and error with the capacitive pads: recalibrate if you ever change soil. I repotted the fern into a mix with more perlite and my old dry-soil number was way off, so it looked thirsty even right after a watering. Took me a week of confused face-planting (pun intended) to figure out the reading scale had shifted. Now I redo the two-point calibration any time the dirt changes. Your kid checking the face every morning is the part I wish I'd kept, though. The lights work but they don't have personality. My niece visited once and asked why my plant was 'so boring' and I had no good answer for her.

I'd push back on the idea that only redrawing when the mood changes is the simpler fix. Those are two different problems. If your face ever animates, like blinking eyes or a little bounce when it switches expressions, you're redrawing constantly anyway and the change-check does nothing for you. I had the same fight with a fish tank temp sign and the only thing that sorted the flicker was keeping the drawing and the sensor reads apart, same as the OP did. The redraw check is still worth having as a bonus, but calling it a replacement for splitting the tasks isn't right.

I've been wanting to try somethig like this for the herb pots on my balcony but I keep getting stuck at the part where the stick-in-the-soil pad talks to the little board. How does that pad actually connect, is it just two wires like the prong ones were? The prong ones I bought last year went brown and crusty after one winter outside so I gave up on them.

Also curious if the pad cares about the soil type. Mine is mostly the cheap bagged mix and it dries out unevenly, wet on top and dusty underneath, so I worry the pad would only see the top part.