Real instructions on getting a Lantronix UDS-10 serial-to-Ethernet bridge working

The Lantronix UDS-10 is rather popular among the AtariAge TI-99/4A crowd. It’s basically one port of a Cisco 2511; it’s a bidirectional telnet-to-serial bridge. The TI folks use it to connect to the outside world, because it is extraordinarily unlikely that the TI will ever get even a ten-megabit PEB card, due to the screwed-up interrupt handling on the TI. It’s also a fantastic alternative to the Commodore 64NIC+, without any of the compatibility problems that go along with it.

A fellow named “Omega” (or “Ohm”; real name elided here) put together a document that purports to describe configuration. I’ll be right up front here and say that I don’t care much for “Omega” (and he doesn’t like me much, either). His antics were a large contributing factor to my departure from AtariAge. I see him as an “ideas man” … not a guy that actually produces anything, but constantly chirps up with “wouldn’t it be cool if somebody did X” and doesn’t understand anything about engineering or technical design.

His UDS-10 document, which I will not link to here, is a good example of that. It’s about 80% correct, but like most things that Omega “creates”, that 20% will kill you. Not a word in the document about what one would do with a UDS-10 fresh off of eBay, with completely incorrect network configuration. No, Omega would have the UDS-10 purchaser install a Windows program to search for the unit, then try to configure it via telnet.

As usual with things that Omega writes, that’ll only work in specific limited cases (i.e., the eBay seller resets the UDS-10 to factory default before shipping) and doesn’t mention the existence of newer/better firmware. But no worries, as the official documentation and firmware is still available from Lantronix. I’ve put up a mirror here, but here’s the general gist of what you want to do:

  • Do not buy a UDS-10- IAP. It will not work properly due to fatal firmware bugs. You want a plain UDS-10. Thanks, IM, for the pointer — I didn’t know there was a difference between the two.
  • Plug the UDS-10 into a serial port (USB, onboard, whatever) connected to a real computer running a real terminal program. Settings are 96008N1. Hold down the “x” key …
  • … while attaching the UDS-10 to power. That’ll force the UDS-10 into setup mode on the serial interface.
  • Hit 0, and set it up for an IP address of to make it do DHCP. Or set the proper IP address for your LAN. I assume that you know your own network better than Omega does.
  • Set whatever other parameters you want here. The important one is the IP address. Once back at the main menu, save and exit.
  • If you are doing DHCP, watch your DHCP server logs for the DHCP lease.
  • If you’re doing static IP, then wait about a minute for things to stabilize.
  • Grab “ltx5805.rom” from either the official Lantronix site or my mirror referenced above.
  • tftp to the UDS-10 IP address. Set binary mode. Execute “put ltx5805.rom 3L”. The UDS-10 will upgrade to the latest firmware and reboot.
  • Hold down the “x” key in the serial terminal while rebooting to get back into setup mode.
  • Choose option 1.
  • Port speed maximum 2400 for TI (9600 for Commodore 64 over user port with UP9600 and so forth), I/F mode 4C, flow 02, port 0, connect mode D6, auto-increment. That’s mostly the same as Omega’s doc, except you want to use 0 for the source port (to randomize) and auto-increment (again, to randomize).

That should do it. Read the official docs for more information on how to use this device; don’t rely on a random shiny PDF floating around AtariAge as an official source-of-truth.

When you get your unit working on your TI, please patronize IM’s resurrected HeatWave BBS at (port 9640). It’s all well and good to telnet into your *NIX boxes to transfer files, but the real fun is the BBS experience.

About Chris Kobayashi

I'm a security systems engineer, specializing in UNIX, network, and physical security. I'm in Tokyo, and I'm mostly retired now. I'm well-versed in both electrical and software engineering, with a particular interest in old computers and game consoles. You can contact me here.
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