The Ultimate USB-C-to-RS-232 Adapter

There are many, many different serial communication architectures and standards. But if you’re working with an old computer or CNC machine, you’re probably looking at RS-232. That DE-9 serial port on the back of the computer, which was ubiquitous for a time, is for RS-232. The problem is that modern computers don’t have them, which is an issue if you want to communicate something that requires RS-232. To solve that problem, Anders Nielsen designed the ultimate USB-C-to-RS-232 adapter.

This is a new, upgraded version of the design, which Nielsen updated because he received such a positive response after releasing the original. Why are people so enthusiastic about it? Because it solves a very real problem.

To explain how, I’ll tell you a quick story. Back in 2016, I bought an old Hurco VMC (vertical machining center) made in 1982. It could read g-code from floppy disks, but that limited the size of the files and therefore the complexity of the parts. The alternative was “drip-feeding” g-code, which required RS-232 communication. Because new computers don’t have RS-232 serial ports, I bought an old computer just for that task. The situation has only become worse in the decade since then, as those old computers become rarer.

That and similar situations are common. Typical adapters on the market are notorious for being unreliable, as precise timing is important.

Nielsen’s adapter is open-source, modular, and extremely flexible. It is modular in the sense that the PCB is in three sections that you can break apart, if you don’t need all of the functions that are available.

And that may well be the case, as Nielsen has seemingly included everything anyone could ever need. Your device is 3.3V? Swap a jumper. Your device has internal RX and TX crossover? Swap a jumper. Your device has some unconventional port? Just solder a header in the provided location and connect jumper wires.

I’m genuinely struggling to think of any scenario that you couldn’t accommodate with this adapter.

And it is affordable, too. The price is just 28,52€ (about $33.00 USD), which isn’t much more than the typical problematic adapters available on Amazon. And because it is open-source, you can simply make your own if you prefer.