another setup using the pi4's own bcm2835 sound card as a sine/square/triangle wave generator(instead of a TLC555)
uses an H11F1 FET optoisolator which gets KEYED on its diode side...
on the 'N' side of this FET OPTO, a continuous sine wave generated by a Gstreamer Script,
is outputted to the pi4 bcm2835 headhpone jack, which is the source of the CW AUDIO NOTE input for a PI4 CW REGENERATION software chain...
the keyed FET OPTO allows the sine wave from the bcm2835's headphone jack output to pass through the FET OPTO
to another pi sound card Line input, a usb sound card, the Behringer UCA222...the LINE INPUT of
and sends it to a midi CW KEYER's midi input port...the output of the CW KEYER is a new AUDIO CW Note
with adjustable rise/fall/pitch/raised cosine/volume the output of the CW KEYER goes to a CW AUDIO BANDPASS FITER
then to a CW LO-MIXER module where the CW PITCH setting of the MIXER tracks perfectly with the CW AUDIO BANDPass settings
the CW keyer, filter and mixer are all modules from RECRI KEYER: