so ive been messing around with an arduino uno i had sitting in a drawer for like two years and finally found a use for it in the shack. the idea is pretty simple — i want it to handle PTT keying for some digital modes and maybe eventually tie in a relay board to switch antennas based on band conditions. im running an IC-7300 and the USB CAT control is already working fine in WSJT-X, but i want to do some more custom automation stuff that doesnt fit neatly into whatever the software offers.

right now ive got a basic sketch going that just monitors a serial command and triggers a relay to pull the PTT line low. its working but the timing feels a little sloppy, like theres a noticeable lag before it actually keys up. not sure if thats a software timing thing or the relay itself being slow. using one of those cheap SRD-05VDC-SL-C relays from a board i got off amazon. wondering if i should switch to a solid state relay or maybe just a transistor circuit instead.

also thinking about adding a Raspberry Pi to the mix to run like a headless logging server or something. has anyone bridged arduino and pi over serial or I2C for a ham project? feels like it could get complicated fast but im curious if its worth the rabbit hole.

yeah the relay lag is almost certainly the relay itself, those mechanical ones have a pull-in time that can be 5-10ms and then theres the debounce situation on top of that. for PTT you really dont need that — just use an NPN transistor like a 2N2222 or even a BC547, collector to the PTT pin, emitter to ground, base through a 1k resistor from your arduino pin. done. no lag worth worrying about and it'll handle the current no problem for a control line.

i did basically the same thing with my 7300 a while back, works great. one thing to watch is make sure youre isolating the arduino ground from the radio ground properly or you might get RF getting into the arduino when you transmit and causing all kinds of weird resets. I had that happen and spent a weekend chasing it before i figured it out. a small ferrite on the USB cable going to the arduino usually helps.

the pi and arduino over serial is actually not that bad, i run that setup for my APRS digipeater thing. pi handles the network side and runs aprx, arduino does the actual hardware interfacing and feeds NMEA from a GPS. communicate over /dev/ttyUSB0 at 9600 baud and its been rock solid for months now.

only gotcha is the pi's 3.3v GPIO if you go I2C route — arduino is 5v logic so you need a level shifter or you'll fry the pi's pins eventually. serial through USB avoids all that since the USB-serial chip on most arduino boards handles the level conversion for you. honestly for what you're describing id just keep it on USB serial and not bother with I2C, simpler and you can debug it way easier.