6 Jan
2008
6 Jan
'08
12:25 p.m.
Hi at all,
as many will have understood, i'd like to make my BigBoard 1 alive again.
I need for a ASCII parallel keyboard.
Many years ago (exactly 20 ones) I got a old cherry keyboard; I open it and
rebuilt all its rows and colums to be the inputs for a KR-2376 keyboard
encoder.
I had much more time..
I though to realize an economical interface to convert signal coming from a
PS/2 keyboard and convert each codes in parallel standard (data 0 to 7 plus
strobe signal).
Here there is a schematic already suggested
http://eece.ksu.edu/~eece696/beta/digital/A/stop.htm but could it works?
What could be the exact schematic and hardware to use? And at the last is
there anything "ready-to-use" cause I have not much time to spend to build
it?
Thanks to all will answer.
Regards
Enrico
7 Jan
7 Jan
8:54 a.m.
It would seem that the cheapest way to do it is a discardable PC.
Input character
print it
loop
3:51 p.m.
On Monday 07 January 2008 11:54, Fred Cisin wrote:
It would seem that the cheapest way to do it is a
discardable PC.
Input character
print it
loop
There was some project article in Byte way back when, by Steve Ciarcia,
which provided a peecee-type keyboard input (AT rather than PS/2 but that
shouldn't make that much difference). The circuit to deal with this was very
simple and elegant, though I can't remember any more just how it was done.
He didn't use a UART or similar, though, just a couple of MSI chips. And I
remember thinking then how it wouldn't be all that hard to stuff an eprom
between the output of that circuit (which gave you keycodes rather than
characters) and have it spit out ASCII.
Perhaps one of these days I'll run across the article again.
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
5:12 p.m.
Roy J. Tellason wrote:
On Monday 07 January 2008 11:54, Fred Cisin wrote:
If you didn't care about sending codes back to the keyboard, then you'd
just need an 11 bit shift register
The previously mentioned
http://eece.ksu.edu/~eece696/beta/digital/A/stop.htm is almost there, it
just needs 1 more F/F
2 LS174s would work for the F/Fs. the CLK line needs to be inverted, but
you can probably get away without doing it.
A divide by 11 counter (LS163 with and AND on bit 0,1 and 3 driving CLR)
should do the trick.
Jim
--
Jim Brain, Brain Innovations (X)
brain at jbrain.com
Dabbling in WWW, Embedded Systems, Old CBM computers, and Good Times!
Home: http://www.jbrain.com
It would seem that the cheapest way to do it is a
discardable PC.
Input character
print it
loop
There was some project article in Byte way back when, by Steve Ciarcia,
which provided a peecee-type keyboard input (AT rather than PS/2 but that
shouldn't make that much difference). The circuit to deal with this was very
simple and elegant, though I can't remember any more just how it was done.
He didn't use a UART or similar, though, just a couple of MSI chips. And I
remember thinking then how it wouldn't be all that hard to stuff an eprom
between the output of that circuit (which gave you keycodes rather than
characters) and have it spit out ASCII.
Perhaps one of these days I'll run across the article again.
8 Jan
8 Jan
1:27 a.m.
Jim Brain schrieb:
If you didn't care about sending codes back to the
keyboard, then
you'd just need an 11 bit shift register
The previously mentioned
http://eece.ksu.edu/~eece696/beta/digital/A/stop.htm is almost there,
it just needs 1 more F/F
2 LS174s would work for the F/Fs. the CLK line needs to be inverted,
but you can probably get away without doing it.
A divide by 11 counter (LS163 with and AND on bit 0,1 and 3 driving
CLR) should do the trick.
The price you then pay is additional effort in the target machine to
parse and decode make/break codes of the keyboard which is usually
significantly more expensive than a $2 PIC or ATMEL. Think of an
Apple-II that wants certain ASCII codes at the parallel keyboard input.
You don't want to modify the system (e)prom to convert
the raw codes returned by the keyboard - no space there for tables. You
also don't want to add a simple conversion eprom at the shift register
output to translate the codes into ASCII as this won't deal with the
break (release key) stuff; it's possible to "ground" unwanted code by
translating them to e.g. 0xff and then use a 7430 to suppress the strobe
signal but yet another circuit then.
No, I am not yet at a point to use a microcontroller just to blink a
LED, which have been done with two cross coupled transistors in the
past, but a PIC is meanwhile the more compact, easier, more flexible
solution to "convert-from-A-to-B" problems.
Regards
Holger
11:46 p.m.
Holger Veit wrote:
No, I am not yet at a point to use a microcontroller
just to blink a
LED, which have been done with two cross coupled transistors in the
past, but a PIC is meanwhile the more compact, easier, more flexible
solution to "convert-from-A-to-B" problems.
I completely agree, but the
OP was interested in an MSI way to get the
data from the KB.
The MSI solution would have problems if the shifting got off by a bit or
two, among others things.
Jim
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participants (5)
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brain＠jbrain.com -
cisin＠xenosoft.com -
elazzerini＠interfree.it -
holger.veit＠iais.fraunhofer.de -
rtellason＠verizon.net