I need a thing. Kind of an odd thing to need in 2020, but it's Land Mobile Radio adjacent and that is a weird space. Specifically, I'd like a way to remotely switch between two DB25 serial connections. I have a VHF radio with a serial interface, and usually it's plumbed into a Radio over Internet Protocol (RoIP) gateway. We can also remotely control that radio over IP, via the serial port and a serial to Ethernet adaptor. There is only one serial interface on the radio. This thing could be living on a mountain top somewhere, with nobody around to switch the knob of the box pictured above.
You can buy one of these things;
They retail at > $1,050,00. That seems like a lot of beer money for a thing as simple as a remote switch, in the age of RasPi. What to do?
Project SwitchPi
Take a RasPi 4, an $8 manual serial switch (the beige one), and a stepper motor. Kitbash them together so that a script on the RasPi triggers a relay which ... runs a stepper, which turns a knob on the beige switch. Or, can we use a relay board to directly switch the needed lines? Or can GPIO and code alone do the switching? How much power goes through these serial lines?
For +/- $60.00, you could get the RasPi, switch hardware, and end up with a friendly Linux box on the same circuit you are using to carry RoIP. Iperf might be handy on that circuit, to name one utility.
You could run the switch (it will be used infrequently) from the command line, or go full-stack and make a simple web GUI running on Apache. I know there's one of those beige switches at the office, I'm going to tear one apart and see what's inside. Probably very simple, especially for $8
Standby for updates,
LabRat
