16 Jan
2012
16 Jan
'12
9:10 p.m.
On 1/15/2012 1:51 PM, Alexandre Souza - Listas wrote:
=> Are crosspoint swithc ICs still easily
available? (It seems that so
many
I would be interested in hearing how one does that. I tried to
implement
such a thing with a 16MHz AVR, but there were issues:
* Some SW scans the KB in interesting ways, so just emulating the std
KB scanning routine triggers was not enough to work.
* On the C64, the joysticks share the KB address lines, so if a user
presses joystick buttons while using the KB, very non standard pins
are connected.
* Some apps scan the KB backwards (ie, drive the columns and read the
rows as opposed to driving the rows and scanning the columns). That
required more code.
I *suppose* you could hook each of the 16 KB lines (assuming and 8x8
matrix) to an interrupt, and then create a table of values for any
combination. But, it seemed easier and more flexible to use a cross
point, especially since I also wanted to allow use of the original KB in
addition to the PS/2 KB.
Jim
--
Jim Brain
brain at jbrain.com
www.jbrain.com
useful ICs are no longer made ;-(). If so,e it
would seem to be posisble
to use one of those to simulate the keyswithc matrix for just avout any
swithc-type keyboard. Add a microcotnroller to decode the PS/2 keyboard
signal then if you detect akey-down code close the appropriate swtich in
the crosspoint array, if you detect a key-up contd open it. OK, there
may
be a little more work for keys that were originally mechancially
locking,
but that's essentially it, I think.
But Tony, I can do everything with a $2 microcontroller...Why the
crosspoint IC? :oO