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<div class="moz-cite-prefix">Mikko Helin wrote:<br>
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cite="mid:CAJ5nAj4zDd_uPixgEzd=Tj-+_roLzkS4wPCKMoaS3uwaB0xOmw@mail.gmail.com"
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<div dir="auto">You could make optical scanner for any keyboard
like an acoustic piano.
<div dir="auto"><br>
<div dir="auto"><a moz-do-not-send="true"
href="https://hackaday.com/2010/10/07/playing-piano-with-optical">https://hackaday.com/2010/10/07/playing-piano-with-optical</a><br>
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<br>
Ah! I have been thinking about optical scanning for a while, such a
thing should worst case get dirty (dust?) and need to be cleaned,
but may last forever, eh?<br>
And probably one could also implement (poly) aftertouch with this,
two birds one stone.<br>
<br>
<br>
And Roman:<br>
Thanks for the warning about "plastic springs", that doesn't sound
very long-lasting...<br>
<br>
- Steve<br>
<br>
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cite="mid:CAJ5nAj4zDd_uPixgEzd=Tj-+_roLzkS4wPCKMoaS3uwaB0xOmw@mail.gmail.com"
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<div class="gmail_extra"><br>
<div class="gmail_quote">19.2.2018 10.59 "Roman Sowa" <<a
moz-do-not-send="true" href="mailto:modular@go2.pl">modular@go2.pl</a>>
kirjoitti:<br type="attribution">
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">That's
exactly how keyboard scanning is done in old organ consoles
you all are talking about now. Not in every one, but usually
in Ahlborn, one of the major european organ makers. The
HC138 decoder is already mounted on the PCB with rubber
contacts.<br>
<br>
I heard from many organ repairmen that rubber contacts fail
first, especially in Fatar keyboards. They literally fall
apart. Probably not an issue for casual mono synth player,
but those kind of organs are heavy banged every day with 10
fingers.<br>
<br>
Don't bother looking for old broken toy synths, they all
have keys made so one octave is made of 2 pieces of plastic,
one white with 8 keys and the other one black with 5 keys.
And the piece of plastic that holds it together is also back
support and return spring. This is also the case in entry
level Yamaha digital pianos.<br>
<br>
Roman<br>
<br>
W dniu 2018-02-19 o 01:29, <a moz-do-not-send="true"
href="mailto:rsdio@audiobanshee.com" target="_blank">rsdio@audiobanshee.com</a>
pisze:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
Steve,<br>
<br>
Since you are writing your own firmware, you might be
interested in one simple way to reduce the number of GPIO
pins needed. Since the Columns in a matrix of switches are
only ever active one at a time, you can use a CMOS 3-to-8
decoder chip. That requires only 3 GPIO pins, but
generates 8 Column strobes. The 4-to-16 variations of the
chips come in both active high and active low variations
(I seem to recall that the 3-to-8 do not). You can just
hard-wire the Enable pin so that one Column is always
active (unless that screws up some part of your circuit
that is shared), and then your firmware can increment a
binary variable that is directly written to the GPIO port
as 3 or 4 bits, as appropriate.<br>
<br>
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