Raspberry PI 4 complete CW KEYER(iambics, st key & keyboard) using free software from LSP Studio Pluins & Recri Keyer

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Chuck Vaughn

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May 10, 2022, 1:13:26 PM5/10/22
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no arduino or teensy usb needed for this CW KEYER...
just a PC, or LAPTOP or RASPBERRY PI 's   sound card LINE INPUT or MIC INPUT(mono only needed)
instead of TEENSY or ARDUINO, this demo setup uses  3 to 4  different 555 oscillators - going into a mono mic input jack...
the 555 timer oscillators are themselves keyed directly/electrically & mechanically by the morse instruments:
  iambic paddles, straight key and a CW KEYBOARD's RIG KEYing JACK output to the 555 OSC input  etc...

Andrew Moore

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May 10, 2022, 1:45:34 PM5/10/22
to 'joe living' via iCW - internet CW
I was thinking about designing an iambic keyer circuit using 555 timer ICs. I didn't know this until recently but when the chip is used in astable mode, to generate a continuous string of pulses, the initial pulse is slightly longer than the subsequent ones because on the first pulse the capacitor has to charge (during the output "on" time) from 0 to 2/3 of the supply voltage, whereas for subsequent ones the cap is already at 1/3 supply voltage so has less charge time.

Also the capacitor charges through two resistors but discharges through only one, so the output-on time is longer than the off time.

So it may be harder than I thought to get well controlled keyer timing out of the 555. You might be able to leverage those qualities to make a decent CFO clucker mode ;)

Chuck, I couldn't tell from your video if the modeled 555 has the same behavior as the real one.

555 info from Wiki

I think it would still be fun to experiment with the 555 for a keyer but for now I'll try the Arduino route.

73
Andrew NV1B
..


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Chuck Vaughn

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May 10, 2022, 2:22:42 PM5/10/22
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555 was just one option... any oscillator will do that is easily keyed by the 
hardware morse instruments - to allow the oscillator to travel from the OSC output - into the LINE/MIC input port of the sound card...

it's the change in pitch...  from 2, 7 , 11, and 19 Khz(prime numbers) that makes the big deal...
since the new Trigger Midi MONO(TMM) app now has a good audio bandpass filter on its input port...
so you can tune out everything but the pitch that will determine the MIDI CW NOTE output timing for that TMM
be it a DIT/dah or st key or cw keyboard keying it... etc...

the 555's in this example represent any tone oscillator CPO  etc...
the 555 does not do any of the critical cw timing work though...just sends a steady Khz tone as per 'keyed by'
dit handle,dah handle, st key or cw keyboard's RIG KEYING jack...  sending a solid steady tone for the duration,
of the mechanical PRESS to close, sending the tone into the sound card's INPUT JACK...   
the RECRI CW KEYER app does all the timing math from there provided by the CW KEYING data
from the TRIGGER MIDI MONO app(s) as per which one is being targeted...




Andrew Moore

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May 10, 2022, 2:28:10 PM5/10/22
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Chuck Vaughn

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May 10, 2022, 2:39:03 PM5/10/22
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one of the unique features of this method is being able to use
a single MONO Mic input (with 3 to 4 different tones)...
to help out LAPTOP's that do not have a STEREO MIC input

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