The rapid progress of computer technology has resulted in many
old, fully-functional IBM AT keyboards being thrown away in favour of newer,
fancier ones. If you’ve ever wanted to connect one of those discarded keyboards
to a project which accepts standard ASCII codes, this AT Keyboard Translator
could be just what you’re looking for.
In operation, the device connects directly to any 101/104-key
AT keyboard with a 5-pin DIN connector and converts the key scan-codes to
standard ASCII "character" and "control" codes. It then outputs these codes in
standard inverted asynchronous format at 300, 1200, 2400 or 9600 baud. The baud
rate chosen depends on your "receiver" and is selected using a single jumper
designated HDR2 on the PC board.
The output data is compatible with the RS-232 serial port of
many devices, allowing you to send text or control codes to your application.
It’s just the shot for interfacing with microcontrollers such as the BASIC
Stamp, Counterfeit and PIC series (in fact, the device was originally designed
to do just that). There really is no easier way to connect over 60 switches to
one pin of a Stamp1, Counterfeit Stamp1, Stamp2 or PIC chip (the non-ASCII keys
are not used).
Of course, it’s not just limited for use with microcontrollers.
It can also interface with other serial devices such as a serial printer (via a
suitable RS232 driver interface) or LCD drivers. One of the photographs with
this article shows the AT Keyboard Translator driving a 4-line alphanumeric LCD
via an "LCD Serial Backpack" (designed by Scott Edwards Electronics).