so i've been messing around with an arduino mega for the past few months trying to automate my yagi rotator and honestly it started as a simple weekend project and now ive got like 4 breadboards on my desk and a half-finished python script running on a pi 4 thats supposed to talk to the arduino over serial but keeps dropping bytes randomly

the basic idea is the pi handles the logging side and interfaces with my logging software via a virtual com port, and the arduino does the actual PWM stuff to drive the rotator controller. been using a cheap ACS712 current sensor to detect when the rotator hits the mechanical stop instead of relying on the potentiometer feedback alone which works surprisingly well actually

main issue right now is the serial communication dropping out. im using 9600 baud which should be plenty stable but every 20-30 minutes i lose sync and have to restart the script. tried bumping up the buffer on the pi side, tried hardware flow control pins, nothing seems to stick. wondering if anyone else has done something similar or if theres a better way to handle this kind of arduino-pi handshaking for long running stuff

also if anyone has opinions on whether i should just ditch the pi and run everything on the arduino with an ethernet shield id be curious, the pi feels like overkill for this but i like having linux available for the logging part

yeah ive been down exactly this hole, took me about 3 months to get my setup stable. the random byte dropping thing is almost certainly a timing issue on the python side - the default pyserial timeout settings are kind of garbage for long running scripts. what worked for me was implementing a simple checksum on every message, like just XOR all the bytes and append it, and then on the arduino side reject anything that doesnt match and send a NACK back. once i did that my script ran for weeks without losing sync

also check if youre running anything else on the pi that might be hammering the CPU periodically. i had the same dropout issue and it turned out to be the automatic security updates kicking in and spiking the load enough to miss serial bytes. disabled that and it got way better immediately. 9600 should be fine for rotator control honestly, you dont need much bandwidth for position data

dont ditch the pi, having linux there is worth it for the logging stuff alone. i tried doing everything on an arduino with the wiznet ethernet shield and while it works its painful to debug compared to just ssh-ing into a pi and tailing a log file

one thing i did on my rotator project was switch from serial to i2c between the pi and arduino which sounds weird but actually worked out better for me since i had the devices right next to each other anyway. though if youre routing cables any distance at all stick with serial or maybe look at RS485 which is what some of the commercial rotator controllers use internally