apolivka@x102a.harris-atd.com (polivka al 60047) (02/26/91)
I would like suggestions on how to _most_easily_ do the following:
I have a organ-like electronic keyboard that does not have midi, but
does have a connector that brings each individual key contact and
"organ-stop" switch out (to two large D-connectors). I would like to
interface that to my Atari 520 ST so that each time I hit a note (or
release one), the Atari gets an indication of that.
Since the Atari has no large connector, I need an interface that scans
the keyboard (through the D-connectors) and does something like a
priority encoder to send a message to the Atari each time it detects a
change in one of the (64) signals (transition from a logic
high-to-low, or vice versa) and of course, send a number indicating
which of the 64 lines it detected this change on. Alternatively, it
could just continuously scan the lines and send out the current status
of each and every line once each scan. (In addition to the 64 notes,
there are about a dozen other switches that would be desireable, but
not absolutely essential to monitor as well).
It is important to recognize that more than one note can be played at
a time (up to a total of 7 or 8 simultaneous notes). The scan rate
must be on the order of 1,000 scans per second or higher in order to
not inject perceptable delays in the playing of music.
Is there something off-the-shelf that I can wire up to a D-connector
that will provide this interface to my Atari?
+--------------------+
+--------+ +-+
| -----| /*--22k resistor-->|D|
| -----| /*--22k resistor-->| |
| -----| /*--22k resistor-->|C|
| | /*--22k resistor-->|O| +------------+
| -----| /*--22k resistor-->|N| | |
| -----| /*--22k resistor-->|N| | I/O | +-------+
| | . |E| | BOX | | |
| -----| . |C| >--->| DESIRED | >-->| ATARI |
| -----| . |T| | | | ST |
| -----| |O| | | +-------+
| | |R| | |
| -----| +-+ +------------+
| -----| |
| | | ^
| -----| | |
| -----| | |
| -----| | This box is what I'm looking for.
| | | It needs to interface with one
| -----| | of the ST's available ports.
| -----| |
| | |
+--------+ |
+--------------------+
NOTE: "/*" in the above figure represents a contact switch at each key
that is connected to a ground bus bar when the key is depressed.
Thanks,
Al
--
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Al Polivka arpa: apolivka@x102a.ess.harris.com
Harris Corporation usenet: uunet!x102a!apolivka
Electronic Systems Sector phone: 407-729-2983
Melbourne, FL 32902
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--
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Al Polivka arpa: apolivka@x102a.ess.harris.com
Harris Corporation usenet: uunet!x102a!apolivka
Electronic Systems Sector phone: 407-729-2983
Melbourne, FL 32902
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