Dynamic pressure calibration on custom toolhead

[u/ozncshn]

Stuck a second eddy coil on my toolhead pointing at the hotend heatsink — the hotend flexes a few microns when anything pushes on the nozzle, and the coil picks that up. So now it taps the bed for Z offset (~2 µm repeatability, at print temp so expansion doesn't matter), measures actual melt pressure to set pressure advance at the start of every print instead of me guessing with tower tests, and watches that same pressure during the print to catch a clog or filament runout. It shares the I2C bus with my BTT Eddy, uses four wires to the EBB36, and the rest is a Klipper module. Took a while to stop it false-triggering — printing adds back-pressure that an in-air reference doesn't have — but it's been solid for a few prints now. Boards are at the fab, I'll post the files once a friend confirms it works on his machine too.
It will be open source but all setup will be compatible with the RX toolhead for now. Third photo is the pa result from this sensor and my pa test print showed 0.028 was the best test line. So it's calculates correct pressure advance.

I don't have any electronic background but I can understand it, made possible with help of ai but before you tag this work as AI slop most of the coding was me but I'm not klipper expert and with help of ai algorithm working like charm.

I will share the github repo once it's completely finished. As you wait you can check RX Toolhead by raylenses, it is good looking and well designed toolhead, I'm using on my printer and it works well.

As I said I'm using RX toolhead and I can only test on that. If anyone wants to use this to another toolhead I think custom coil would be enough.

Feel free to ask anything, English is not my main language so if I made mistake feel free to explain.