[GreenKeys] Precise Baud Timing

[Windows XD]

OK now this is kind of embarrassing: my program and setup was completely
fine. One of the type bar carriage actuating arms was not adjusted
correctly and typing incorrect bits half the time, leading to my problem.
Once I fixed it, my program worked flawlessly in its pre-debugging state.
Thank you all for your help though, and I may build a system like that
sometime in the future!

On Wed, Nov 12, 2025, 7:23 PM Harold Hallikainen via GreenKeys <
greenkeys at mailman.qth.net> wrote:

> I am doing something similar in the DSP TU (
> https://w6iwi.org/rtty/DspTU3/ ).
>
> https://github.com/HaroldHallikainen/DSP_TU2/blob/master/src/dds.c
> generates the AFSK using simple DDS.
>
> https://github.com/HaroldHallikainen/DSP_TU2/blob/master/src/BaudotUart.c
> does ASCII to Baudot conversion, Baudot to ASCII, and transmit and receive
> uarts.
>
> DDS AFSK to a file is also described at https://w6iwi.org/rtty/audio/npr/
> .
>
> Harold
> https://w6iwi.org
>
>
> On Wed, November 12, 2025 1:09 pm, Zach Tumbusch wrote:
> > I went through a few iterations testing with Node, PHP, and C# but
> > settled on this example. The bigger challenge was sorting the popping on
> > the fast frequency transition. I tested this up to 9600 baud with my
> > ST-8000. The
> > bit stream is 8 bit characters  "A": "01100011" 11000 with 1 start bit
> and
> >  2 stop bits. The actual bitrate at 45.45 baud is around 22ms. but since
> > I
> > am directly converting points to a wav file I keep track of that based on
> > how many samples. Prints well on all my machines. Model 28 / UGC-136BX /
> > Hal. See the working example. https://w8zjt.net/itty
> >
> >
> > 73, de W8ZJT
> >
> >
> > async generateAFSKWav(bitstream: string, baud, mark, space): Promise<
> > Blob> {
> > const sampleRate = 16000;  // Sample rate in Hz const fadeDuration = 50;
> > // Number of samples for smooth
> > frequency transition const samplesPerBit = Math.round(sampleRate / baud);
> > const totalSamples = bitstream.length * samplesPerBit; let audioSamples:
> > Float32Array = new Float32Array(totalSamples);
> > let phase = 0.0; let currentFreq = bitstream[0] === "1" ? mark : space;
> let
> > currentPhaseIncrement = (2 * Math.PI * currentFreq) / sampleRate ;
> >
> >
> > for (let bitIndex = 0; bitIndex < bitstream.length; bitIndex++) { const
> > newFreq = bitstream[bitIndex] === "1" ? mark : space; const
> > newPhaseIncrement = (2 * Math.PI * newFreq) / sampleRate;
> >
> > for (let i = 0; i < samplesPerBit; i++) { if (i < fadeDuration) { //
> Smooth
> > frequency transition (interpolation) const fadeFactor = i / fadeDuration;
> > const interpolatedFreq = currentFreq * (1 - fadeFactor) + newFreq *
> > fadeFactor; currentPhaseIncrement = (2 * Math.PI * interpolatedFreq) /
> > sampleRate; } else {
> > currentPhaseIncrement = newPhaseIncrement; }
> >
> >
> > // Generate waveform sample
> > audioSamples[bitIndex * samplesPerBit + i] = Math.sin(phase );
> > phase += currentPhaseIncrement;
> >
> > if (phase >= 2 * Math.PI) { phase -= 2 * Math.PI; }
> > }
> >
> >
> > currentFreq = newFreq; }
> > // Convert to WAV format
> > const wavBuffer = await WavEncoder.encode({ sampleRate: sampleRate,
> > channelData: [audioSamples] // Mono channel
> > });
> >
> >
> > On Wed, Nov 12, 2025 at 1:57 PM Steve <zarco at sonic.net> wrote:
> >
> >
> >> Much easier to do in hardware with just a few chips.
> >> 555 timer and shift register. A couple more chips and
> >> send R-Y test. You can use a scope or period counter to accurately setup
> >> the 555 clock. Can be implemented in Baudot or ASCII.
> >>
> >> With a uP, use the programmable timer which in most these
> >> days is internal. This should be largely independent of the code if done
> >> right.
> >>
> >> Projects like this are fun...enjoy!
> >> Steve W6SSP
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> >>
> >>
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> >>>>>
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> >>
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> >>
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> >>
> >>
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> >>
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> >
> >>>> Jordan Spencer Cunningham's GreenKeys Search Tool:
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> >>>>
> >
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>
>
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> >>> 2002-to-present greenkeys archive:
> http://mailman.qth.net/pipermail/greenkeys/
> >>> 1998-to-2001 greenkeys archive:
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> >>> Randy Guttery's 2001-to-2009 GreenKeys Search Tool:
> http://comcents.com/tty/greenkeyssearch.html
>
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