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I have a very specific problem. I need to communicate between two computers (Intel NUC and a Jetson TX2, both running linux to be specific). I cannot use wireless, and the ethernet ports are occupied by other devices. I need a very simple low bandwidth communication between those two computers.

So my plan is to make a small pcb with two FT232RL chips, and connect them like this: Computer 1 -> USB -> FT232RL <=> FT232RL <- USB <- Computer 2. I assume that this would work like a serial port between the computers.

Will this work? Is this a good solution, or is there something better?

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    \$\begingroup\$ Why design a board while you can get two USB to serial cables and connect them together? You can even choose if you want standard 9 pin RS232 cables so all you need is a null modem cable between them. Or two USB to TTL cables and you can solder them to a single cable. \$\endgroup\$ – Justme Mar 11 '20 at 21:46
  • \$\begingroup\$ I forgot to mention that I am constrained by weight and dimensions, the smaller and lighter the better. But looking at these cables, some of them look quite good, thanks for the advice. \$\endgroup\$ – Dan Mar 11 '20 at 21:50
  • \$\begingroup\$ You need some parameters in here, 'low' bandwidth is a very subjective term in a gigabit/sec world. Yours could be 100 bytes/sec, 500 kbytes/sec or something else. \$\endgroup\$ – TonyM Mar 11 '20 at 21:58
  • \$\begingroup\$ Around 100 kbytes/sec is the most I would need. \$\endgroup\$ – Dan Mar 11 '20 at 23:02
  • \$\begingroup\$ I am curious why wireless is not an option. Are you not "allowed" to use it? \$\endgroup\$ – Christian B. Mar 12 '20 at 7:14
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SLIP and PPP were designed for this very purpose: IP connections over serial links. Just get the two adapters and connect them with a ‘null modem’ (crossover) cable, set up pppd or slipd. Done.

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Yes, it will work, just like two serial ports connected in a null modem would. But no, it's not a very good solution considering other solutions.

These other solutions are more general computing than anything. It's easier to just purchase a solution that's proven.

  1. Use a switch. The devices already have ethernet. If they are one the same network, you are done. This is the entire point of networking.

  2. Use a router and port forwarding. Basically complicated version of 1.

  3. There are USB to USB bridge cables, but these typically need drivers installed, and are antiquated.

  4. There are USB to Serial (RS232 or TTL) that you can just wire to each other, but this is as good as a solution as you home brewing one. You will need to configure low level serial communication at the OS or App level.

  5. Usb to Ethernet adapters. Off the shelf these tend to be plug and play, all you do is set up a static IP address for the new network interface, and you're basically at option 1.

Finally, the most electrical engineering solution.

  1. Use the built in serial TTL ports on both the Jetson and the NUC. Both are IIRC 3.3v so you literally just need 3 wires (TX, RX, Ground) and no extra parts. If they are at different voltages, there are cheap boards to do level translation or you can use a simple transistor based translation.
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Ten-fifteen years ago there used to be USB-to-USB connect "cables", Type-A on both ends, and some "bridge" in between. Not sure what USB class was employed, but file transfer was available. enter image description here

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