so ive been messing around with this idea for a while now and finally started actually building it. basically i want to use an arduino mega to handle all my antenna switching automatically based on band — right now i have a 40m dipole, a 20m yagi, and a 6m halo up on the roof and im constantly having to manually flip relays when i change bands on the rig. its not the end of the world but its annoying especially during a contest.

the plan is to read the band data output from my IC-7300 (the CI-V serial stuff) and have the arduino parse it and then fire the right relay. i got a bunch of those SRD-05VDC-SL-C relays from amazon, probably overkill but they were cheap. im using a ULN2003 darlington array to drive them so im not pulling directly from the arduino pins.

my question is whether anyones done something similar with the CI-V interface specifically. ive seen some sketches online but most of them are for older rigs and i cant tell if the baud rate stuff is the same for the 7300. also wondering if a pi would be better for this since i already have a pi 4 sitting around doing nothing. seems like overkill for just switching relays but maybe if i wanted to add logging or a web interface later it would make more sense.

anyway if anyones built something like this id love to see your code or at least hear how you approached the CI-V parsing part

yeah i did almost exactly this with a 7300 about a year ago. the CI-V on that rig defaults to 19200 baud but you can change it in the menu — i think mine is set to 9600 just to keep things simple. the format for the frequency data is pretty standard icom stuff, you're looking for the FE FE stuff in the byte stream. there's a library called ICOMLib or something similar on github that someone wrote for arduino, saved me a ton of headaches trying to parse it manually.

one thing i ran into — make sure you're using a proper TTL to RS232 level shifter between the arduino and the rig if you're going into the actual serial port. if youre using the USB then you can just treat it like a regular serial device from the computers side and have the arduino talk to the computer instead, which is what i ended up doing actually. bit of a roundabout way to do it but it meant i could also tie it into log4om for logging at the same time.

the ULN2003 approach is solid btw, thats exactly what i used. just watch your relay coil current if you stack a bunch of them.

pi is definitely overkill for just the switching but honestly once you go down that road you end up adding stuff anyway so maybe not a bad idea to start there. i built a whole shack automation thing on a pi 3b+ — remote PTT, rotor control, band switching, and a little flask web app so i can see whats happening from my phone. took way longer than expected but its really nice now.

that said if all you want is the relay switching an arduino is way simpler to get running fast and you dont have to deal with linux and SD card corruption and all that pi headache. had a pi zero kill itself mid-contest once because the filesystem got corrupted and that was not fun. arduino just runs the loop forever and doesnt care.