nanog mailing list archives

RE: Digi TS8 serial console server funkiness


From: George Bonser <gbonser () seven com>
Date: Thu, 8 Mar 2012 03:06:04 +0000


Other issues I've noticed..cannot use arrow keys to search command
buffer.

This is going to be a tougher one.  Might be a difference in character encoding. Here is the VT100 spec:

http://www.handshake.de/infobase/dfue/prgrmmer/t322.htm

*  ESC D             cursor down - at bottom of region, scroll up
*  ESC M             cursor up - at top of region, scroll down

...

Arrows      Standard       Applications     IBM Keypad
   Up        ESC [ A        ESC O A          Alt 9
  Down       ESC [ B        ESC O B          Alt 0
  Right      ESC [ C        ESC O C          Alt -
  Left       ESC [ D        ESC O D          Alt =

So you probably need to check your keyboard encoding.  It likely differs from VT100 escape sequences.

Also, if you have several devices connected to that terminal server, see if you have one that is spewing debug or other 
information out the console port. That one might be causing some buffer overrun situations or keeping the CPU busy so 
it loses characters.  Line noise can cause garbled data, too.  But I would try flow control first.  One thing I have 
seen before also is ground loops causing issues.  Some serial devices actually tie signal ground to chassis ground.  If 
you have a cable connecting two such devices and there is some ground potential difference, you can create a ground 
loop and introduce noise (and things like sparks, fire, blown fuses, etc.) if the ground potential difference is great 
enough between the two devices.


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