so ive been messing around with an arduino mega for the past few weeks trying to get it to control my 4-port coax switch automatically based on what band the radio is on. the idea is to pull the band data off the CI-V bus from my IC-7300 and then have the arduino decode that and fire the right relay. in theory its pretty simple but im running into some weirdness with the serial parsing and im not sure if its a timing issue or if im just reading the CI-V packets wrong.

the relay board im using is one of those cheap 8-channel ones from amazon, 5v coils, and it seems to work fine when i just hardcode which relay to trigger. the issue is specifically with the CI-V reading part. ive got it pulling data over a MAX3232 level shifter but every so often it seems to drop bytes and then the band decode goes completely wrong and it tries to switch to the wrong antenna.

anyone done something similar? or honestly any CI-V over arduino project would be helpful to look at. ive been at this for like 3 weekends and its starting to get frustrating. also wondering if a raspberry pi would have been a better choice for this kind of thing but i feel like the arduino should be able to handle it, its not that complicated

yeah i did almost exactly this for my shack like two years ago, except i was using a TS-590 so kenwood CAT instead of CI-V, but same basic idea. the byte dropping thing is almost certainly a buffer overflow on the arduino's hardware serial - if youre using Software Serial for CI-V that thing is notoriously flaky especially if anything else in the loop is blocking. even a small delay() call in the wrong place will cause you to miss bytes.

what i ended up doing was switching to one of the hardware serial ports on the mega (you have 4 on that board which is great) and then just making the main loop as non-blocking as possible. no delay() anywhere, just state machines and millis() for timing. its a bit more code to write but once you do it that way it just works. also double check your baud rate matches exactly what the 7300 is putting out, CI-V is usually 19200 but some people have theirs set different and its easy to miss.

raspberry pi would work too and you'd have more headroom for sure but honestly the arduino is fine for this, you just gotta be careful about blocking code

i built something similar but went the pi route and kinda regret it in some ways. the latency on gpio from a pi running linux is not great if you need really deterministic timing, though for antenna switching it probably doesnt matter that much honestly. for pure relay control an arduino or even a bare attiny is way more predictable.

that said if your problem is the CI-V parsing the pi does make that easier cause you can just write python and use pyserial and theres already libraries floating around for CI-V. there was a project called hamlib that has CI-V support built in and you could probably hook into that instead of rolling your own parser. might save you a lot of headache. either way good luck, this kind of shack automation stuff is super satisfying once it actually works