so ive been messing around with a raspberry pi 4 for the past few months trying to get it to do... well, everything. started out just wanting a direwolf setup for APRS and packet but then i started thinking about using it to control my antenna switch, log contacts automatically, maybe tie into weather station data for the shack display. you know how it goes, scope creep happens fast.

anyway the actual APRS side works great, direwolf is pretty solid once you get the audio levels sorted out which took me longer than i want to admit. my issue right now is the gpio stuff for the antenna relay switching. im using a 5v relay board i grabbed off amazon, 4 channel thing, and i cant get the logic levels quite right — the pi's gpio is 3.3v and the relay board wants 5v trigger. most of the time it works but occasionally a relay just kind of... chatters? not great when youre switching between bands mid-contest.

was wondering if anyone has gone down this road and whether its worth adding a proper level shifter or if theres a relay board that plays nicer with 3.3v logic. also open to being told im overcomplicating this and should just buy a hamlib-compatible switch.

yeah the 3.3v to 5v thing bites everyone at least once. those cheap relay boards usually have an optocoupler that wants a proper 5v signal to trigger reliably — 3.3v is kind of in the grey zone depending on the specific board you have. some of them actually work fine on 3.3v, some dont, total lottery.

easiest fix ive found is a BSS138 based level shifter, you can get a little sparkfun board or the adafruit one for a few bucks and it cleans everything right up. alternatively if you want to avoid the extra board, look for relay modules that specifically say "active low" with optocoupler isolation and are labeled 3.3v compatible — they do exist. sainsmart has some that work fine direct from the pi gpio without any drama.

the chatter is probably just the marginal trigger voltage causing the coil to not fully latch. once you get solid logic levels that should go away. i ran a similar setup for about two years driving a 6-position antenna switch and it was completely reliable after sorting the level issue.

honestly i went through almost the exact same rabbit hole last winter. ended up just throwing an arduino nano in between the pi and the relays as kind of a dumb IO expander — it handles the 5v logic for the relays, takes simple serial commands from the pi, and i dont have to worry about the gpio voltage stuff at all. probably overkill but i had a spare nano sitting on my desk doing nothing so whatever.

the direwolf aprs side is rock solid for me too. only thing i'd say is watch your audio interface — i was using the built in pi audio and getting occasional decode misses, switched to a cheap USB sound dongle and it got noticeably better. something about the onboard audio being electrically noisy near all the other stuff on the board i think.