High Performance Raspberry Pi4 /midi keyed\ Morse Code Practice Oscillator with a tracking BP filter

this video demo's a RASPBERRY PI 4, SETUP as a high performance morse code practice oscillator using RECRI KEYER CW modules


TEENSY-LC usb midi board with recri midi-keys embed firmware https://github.com/recri/keyer/tree/master/embedded/MidiKeys


fldigi is keying an H11F1 FET OPTO ISOLATOR DIODE SIDE other side of FET CHIP connects together 2 pins of the TEENSY USB MIDI BOARD that ejects a MIDI NOTE 2 to the Pi4 VIA USB CABLE... the RECRI KEYER's keyer-tone module is keyed by midi note "2" and send a raised cosine shaped pure sine wave cw note to the next SDR MODULE FILT which is a bandpass filter set according to OP's preference the filter sends its audio output to the input of the next SDR MODULE LO-MIXER which outputs any CW pitch you want according to its front dial, which can be adjusted by a TOUCH MONITOR on the pi(or by mouse)

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Comment by Chuck aa0hw on July 22, 2022 at 10:48am

High Performance Raspberry Pi4 /555 keyed\ Morse Code Practice Oscillator with a tracking BP filter

this is a follow up video from the first one here:


in this video, instead of using MIDI to key the PI4 CPO...a simple 'keyed' TLC555 square wave oscillator is keyed and the output of the 555 sends its square wave at 7Khz to the PI4's USB sound card's LINE INPUT

then 'inside' the PI4, it goes straight over to the sidechain input of ZAMGATE which is holding back a pure sine wave at 1Khz...once the sidechain port is triggered by the incoming 7Khz square wave from the TLC555(which is being keyed by FLdigi's serial port RTS pin/ground, connecting the 555's pin 4 to its pos rail) it allows the pure sine wave at 1Khz to pass through the upper gates, and go into the 1Khz bandpass filter.... the output of the bandpass filter goes to a RECRI KEYER SDR LO-MIXER module that allows any CW PITCH to be chosen while still tracking the bandpass filter's width and 'Q'... no matter what freq the LO chooses the CW pitch to be...

to get the proper CW element length to match the incoming 555 cw element length....the threshold setting of ZAMGATE is set using FLdigi to send dits out at 120 wpm - which should each be at 10 milliseconds length... then the threshold setting of ZAMGATE is adjusted to match the 555 dit length - outputting a 10 ms cw element length of the pure sine wave connected to its upper ports...

the PURE SINE WAVE oscillator, filter and LO-MIXER are all modules from

Recri Keyer:    https://github.com/recri/keyer

ZAMGATE is a plugin from:    https://www.zamaudio.com/


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