another possible DiY QRQ CW 'KEYed' SINE WAVE CPO to use for the MUMBLE INPUT - uses 7 FREE EURO-RACK MODULEs

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Chuck Vaughn

Jun 20, 2022, 10:33:32 AM6/20/22
to iCW - internet CW
QRQcardinal77wpm.pngHERE is a VIDEO DEMO of this CPO in action
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Chuck Vaughn

Jun 21, 2022, 3:06:19 PM6/21/22
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Here is yet another method for getting a nice sounding CW SIDETONE into the MUMBLE INPUT 
using a Raspberry PI, an OPTO-ISOLATOR & a 555 timer chip square wave running continuously...
both the OPTO-ISOLATOR and the 555 TIMER chip are being powered by the PI's  gpio pins...

the OPTO-ISOLATOR is   "keyed"  by an external CW KEYER's RIG KEYING JACK... 
which then passes the 555 square wave that is running through the opto-isolator's output pins
and then into the PI's usb sound card's  line input...  
being a square wave with harsh harmonics and no edge shaping of any kind....this would sound horrible !
so.... this single GSTREAMER SCRIPT  depletes every harmonic OUT of the square wave  AND then places
a raised cosine edge onto the RISE & FALL time
gst-launch-1.0 -v jackaudiosrc do-timestamp=true  ! "audio/x-raw, rate=48000" ! queue !  audioconvert !  
ladspa-zamgate-ladspa-so-zamgate   attack=.1 release=.1 threshold=-22 !    audiorate !   audioconvert ! 
audiowsincband mode=band-pass lower-frequency=698 upper-frequency=898 length=567  window=3 low-latency=true  !
  queue !   audioconvert ! jackaudiosink  buffer-time=5000        

this setup operates at near zero latency -

please see the video description notes for more info...   
here is the LIVE DEMO VIDEO example of this operation:
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