so ive been messing around with this for a few weeks now and im not totally sure im going about it the right way. basically i have an old yaesu G-450A that i want to control automatically based on where the DX is coming from instead of manually twisting the knob every time. the idea is to have the pi zero read az/el data from whatever logging software im running and just... turn the rotator to match.

problem is im not sure how to interface the pi with the actual rotator controller. the G-450A has that 8-pin DIN on the back for the control cable but i assume i cant just wire that straight to the GPIO pins without some kind of buffer or voltage divider situation. been looking at some schematics online but half of them are for different rotators or assume you already know what youre doing with electronics which i sort of do but not always.

has anyone built something like this with a pi zero specifically? i thought about just buying one of those hamlib-compatible USB adapters but that feels like cheating and also its like $80 which seems way too much for what it does. curious if anyone has a rough circuit they used or at least some pointers on where to start.

yeah done almost exactly this with a pi 3 not a zero but the concept is the same. the short answer is you definitely need level shifting between the pi GPIO and the rotator controller — the G-450A runs on 5v logic for its control lines and the pi is 3.3v, so straight connection will either not work reliably or you'll fry the GPIO pins eventually. i used a simple BSS138 level shifter board, cost like a dollar fifty on ebay and does the job fine.

the azimuth sense line from the rotator is actually an analog voltage that varies with position, so you'll also need an ADC since the pi has no analog inputs natively. i used a MCP3008, which is SPI and works great with python. then you just read the voltage, map it to degrees, and close the loop with a little PID controller or even just simple bang-bang control if you dont need it super precise.

hamlib has rotctld which can run on the pi and expose a network interface so your logging software can talk to it. thats honestly the cleanest part of the whole thing once you get the hardware sorted. the $80 adapters are mostly just doing what youre trying to do yourself so yeah, worth building it.

i built something similar a while back except i used an arduino nano instead of a pi for the rotator interface part and then had the pi just act as the controller sending commands over serial. worked fine but in hindsight i probably shoulda just done it all on the pi and skipped the extra board. anyway the point is the voltage stuff the other guy mentioned is real, dont skip that step.

one thing i'd add — watch out for the motor relay timing on the G-450A if you're sending lots of small corrections. those old controllers dont love being jogged rapidly, mine started making a weird clicking noise after a while and i had to add some deadband to the control loop so it doesnt try to correct every half degree. probably obvious but it wasnt to me at first.