Looking for HP 98155A (aka 09915-68000) keyboard

[Tony Duell]

> 
> On the topic of matrix conversions...
> Going from one device matrix to a controller expecting another
> is something like converting one set of 24 lines to another 24.  To do
> it in PIC's would take two, unless there were such things as matrix to
> serial encoders and decoder chips.  Anybody make them?

To stick with the 9915 keyboard for the moment.

The Matrix is something like 11 * 8 (or is it 10*8?). And from what I 
rmember, only 1 key in the matrix is ever 'down' at a time. I was going 
to simulato that by a couple of analogue muxes back-to-back (if you see 
what I mean), then I cna feed in the right select codes and effectively 
press a key.

Shift and Control are handled spearately (they have their own pins on the 
DB25 connector), an open-collector output for each would do.

For machines that need have several keys pressed at once, there was (is?) 
a 4*4 crosspoint switch IC in the 4000 series CMOS. There's proably 
something like it still available.

I was going to use a normal PC/AT keyboard, which has an intenral 
microcontroller to do the scanning. Feed the serial output of that into 
my onw microcontroller that then controls the muxes, etc.

-tony