so ive been messing around with an arduino mega for the past few weeks trying to get it to control my 4-port antenna switch automatically based on what band my radio is on. the radio outputs band data on a DB9 connector (its an IC-7300) so in theory i should be able to read that and then just drive some relays accordingly. i got the relay board working fine, and i can read serial data no problem, but the band data format from icom is a little weird and im not 100% sure im decoding it right.

the other thing i havent figured out yet is debouncing the relay switching so it doesnt just hammer the relays when the radio is doing its thing during a QSY. thinking maybe just a 500ms delay but that feels sloppy. anyone done something similar or have code laying around they wouldnt mind sharing? im not a great programmer but i can muddle through C++ well enough to modify stuff.

yeah i did almost exactly this with a 7300 about a year ago. the CI-V band data isnt too bad once you get the format down, theres a table in the icom manual appendix but its easy to miss. basically youre looking for specific hex values that correspond to band ranges. i ended up just mapping the frequency output rather than the discrete band data signal — pull the frequency over CI-V every 200ms or so and decide the band yourself in code. way more flexible and you dont have to deal with the band voltage pins at all.

for the relay debounce i used a simple state machine, if the target band changes i start a 300ms timer and only switch if it hasnt changed again by the time the timer expires. works great, no chatter. i can dig up the sketch if you want, its not pretty but it works.

i did something like this but with a raspberry pi instead of arduino, mostly because i already had one sitting around and wanted to run fldigi on the same box. ended up being overkill honestly. for just driving relays arduino is probably the right call, pi gpio can do it but the timing is less predictable because of the OS getting in the way. the 500ms delay thing is fine for antenna switching, relays dont care and your SWR meter isnt gonna explode or anything. dont overthink the debounce.