so i've been messing around with an arduino mega for the past few weeks trying to build my own rotator controller and honestly its gotten a bit out of hand. started simple enough, just wanted to replace the old green heron controller that died on me, figured how hard could it be right

anyway im using a stepper motor with a hall effect sensor for position feedback and writing position data to an eeprom so it survives power cycles. thats all working fine now. the part thats killing me is the azimuth calibration, i can get it close but its drifting maybe 3-4 degrees over a full rotation and i cant figure out if thats the sensor placement or just noise on the analog pin. running a 10k pulldown and even tried adding a small cap to filter it but still getting the drift.

also started looking at throwing a raspberry pi 4 in there to run hamlib and talk to my ic-7300 at the same time so i could do some basic skimmer stuff and auto-point the yagi at spotted dx. pi is doing fine for that side of things but now i have two separate systems that dont really talk to each other well yet. thinking about using i2c between them or just serial over USB, not sure which makes more sense for this application.

anyone done something similar or have thoughts on the sensor drift thing, thats the most annoying bit right now

the drift is almost certainly noise on the analog pin, i had the exact same issue with a pot-based position sensor on mine. try averaging like 10-20 reads in software and throwing out the outliers before you do anything with the value. made a huge difference for me. also depending on how long your wire runs are from the sensor to the arduino you might be picking up interference from the motor itself, shielded cable helped me there.

on the pi to arduino comm thing i'd just go serial over USB honestly, i2c is fine but its fussier to get right and you dont really need the speed for rotator control. pyserial on the pi side is dead simple and you can have them talking in like an hour. i ran something similar for a while before i just moved everything to the pi with a motor hat and cut the arduino out entirely, but either way works.

yeah ive gone way too far down this exact hole lol. my setup started as a simple az/el controller and now theres three pis and like five arduinos in my shack doing various things and honestly i cant remember what half of them do anymore. the hamlib integration on the pi is great once you get it sorted, the ic-7300 plays really nicely with it over usb. for the skimmer stuff you might want to look at whether the pi 4 can keep up under load, mine gets a bit warm doing rtty decoding and rotator stuff at the same time but nothing crazy with a heatsink on it.