so ive been messing around with an arduino mega for the past few weeks trying to get it to handle my antenna switching automatically based on band changes from my IC-7300. the radio puts out band data on the ACC port and i figured i could decode that with the arduino and drive a set of relays to switch between my verticals and the yagi up top.

got most of it working but im running into a weird issue where the relay for 40m keeps triggering a split second before the band data is fully settled — like there's some bounce or timing thing happening on the input lines. ive got 10k pulldowns on all the band data lines already so its not a floating input problem, just seems like the arduino is reading partway through a transition or something. debounce in software maybe? or is there a better way to handle this with the hardware side

also kind of wondering if i should just scrap the mega and move this over to a raspberry pi zero, since i could log everything and build a little web interface to see what antenna is active. but that feels like overkill for what is basically a relay driver. curious what other people have done

yeah the band data from icom radios has a small settling time before all 4 lines are stable — i ran into the exact same thing with a homebrew bandpass filter switcher i built a couple years ago. what worked for me was just adding about a 50ms delay in the arduino after detecting any change on the band data lines before i actually acted on the new value. not the most elegant solution but it works reliably and the switching is still way faster than anything that matters in practice.

on the pi zero idea — i actually do run a pi for my shack automation stuff but i keep the actual relay driving on a separate arduino nano just because the pi's GPIO isnt great for time-sensitive stuff and you dont want a kernel hiccup firing your relays at the wrong moment. the pi talks to the nano over serial and handles all the logging and web ui stuff. best of both worlds honestly and a pi zero is like five bucks so why not

might be worth throwing a small RC filter on those band data lines too, like a 100 ohm resistor and a 100nF cap to ground before the arduino input. cleans up transition noise real quick and i find it pairs nicely with a short software delay. dont overthink it though, these icom band decoders are pretty well documented at this point and people have been building exactly what youre doing for years. look up the RemoteHams forums, theres some good schematics floating around