Re: [TCLUG:18425] RS232 keyboard

[psp@printwareinc.com (Phil Plumbo)]

> A co-worker had suggested a device manufactured by
>BlackBox (tm) that is a PS/2 <-> RS232 converter (rumored to be part
>#IC813A).  I wish I knew what that device did...
 
FWIW...The output of an AT keyboard is a serial TTL-level data stream of
make-break keycodes. The keycodes are assigned to the keyboard keys from
left to right, top to bottom. Your PC's BIOS converts these keycodes into
ASCII (when possible).

A "make" is indicated by the keycode itself, a "break" indicated by a break
code (0xF0) followed by the keycode. So the break sequence for key #1 is
0x01, 0xF0, 0x01. 

The Blackbox widget converts this TTL-level serial data stream into an
RS-232-level ASCII data stream (although, strictly speaking, the keyboard
can generate characters that are outside the ASCII character set).




Philip S. Plumbo           | Printware, Inc.
psp@printwareinc.com       | 1270 Eagan Industrial Rd. | voice: 651-456-1400
http://printwareinc.com    | St. Paul, MN 55121  USA   |   fax: 651-454-3684