Choose the option that best describes you.

Sunday, 20 November 2011

mmm, blueberry serial

With all the networking gear and headless servers and whatnot I manage, I still frequently use RS-232 connections. Since it's been a long time since I had a computer with a built in serial port, I have a couple USB-serial adapters I use for this purpose. I just found another one in a drawer and thought it would be nice to have hooked up to my other computer so I don't have to move the adapters around. What I found is an old blueberry-iMac themed Belkin F5U103 USB-serial adapter. I connected it to a router console and to my computer and it was recognized by Linux 3.0.0 and attached to /dev/ttyUSB0, but despite the apparent flow of data (this thing has some status/activity lights) I couldn't get a router prompt or anything human-readable using kermit or minicom. This adapter has supposedly been supported in Linux for a long time, but I wasn't finding any useful info about making it work for me. I was about to give up and assume it was defective until I stumbled onto this post about FreeBSD users testing the same adapter back in 2003: http://markmail.org/message/6snsp5cndmakspzs

Hmmm... " an off-by-1 error in the speed setting code"? I reconfigured kermit for 4800 baud instead of 9600 and sure enough, it works. You just have to set the port speed to the next slower standard rate than expected by the connected device.