[GreenKeys] Fwd: Old Dog with some New Tricks.

Thu Aug 29 00:33:57 EDT 2024

Sounds like a fun project!

On AFSK generation, are you just outputting a square wave at the mark or
space frequency? This, of course, can be run through an LPF to remove the
harmonics. Even running it directly into an SSB transmitter would probably
be fine since the filters in the transmitter would attenuate the
harmonics.

In the DSP TU (https://w6iwi.org/rtty/DspTU2/ ), I am generating a sine
wave using software DDS. Since the PIC32MZ does not have a DAC, I'm
outputting the analog levels (result of the sine function) on an 80 kHz
PWM output. That goes through a 4 kHz active LPF.

I have a button that selects wide or narrow shift. The system
configuration has the center frequency and shift for each of these. The
default for wide shift is a center frequency of 2 kHz.

All configuration is saved as text in an external flash chip and run
through a command interpreter on power up.

How are you demodulating the received AFSK? I'm doing the DSP equivalent
of a typical two tone filter TU. An old software block diagram is at
https://w6iwi.org/rtty/DspTU/DspTuHw221023.pdf#page=7 . It has changed
some since then, but is similar.

So, it sounds like you have an interesting project! I look forward to
seeing more information about it.

Harold
https://w6iwi.org

On Wed, August 28, 2024 7:46 pm, John Spigel wrote:
> The RazPi has been an adventure for me. I always wondered why there was
> little information for using the gpio pins that came on the many mini
> itx motherboards I've used all these years. Now I know what I can do
> with them. The RazPi comes with many informative internet sources and
> helpful pieces of code. There is not much you can't do with them in
> software. I will provide much of the software I've assembled eventually
> on my website.
>
> Now a progress report: It's been tough, but oday I was able to get my
> Python coded fsk-gpio pins working which eventually be able to key a
> loop with an optical SSR relay. I have two gpio pins following the fsk
> tones from ITTY and from text/image files. Presently they are only
> flickering LEDs, but I will add some circuitry for a 60ma loop. Also I
> have two more gpio pins to simultaneous create PWM tone outputs with a
> 170 shift of 2125/2295 and 850 shift 1575/2425. A little bit of RC
> filtering should make these suitable for our needs.
>
> I am concerned about latency. I'm only able to test on an M15. But I'm
> thinking that 100WPM should work, too.
>
> Any suggestions for additional M/S pairs? I haven't looked at user
> configuration options yet, but I will eventually add to the code to make
> it flexible.
>
> 73, John W!AN
> --------------------------
>
> Hey John -
>
> This all sounds really cool.Â  Don't know why I never thought of using BT
> to talk to my TU.Â  I'm constantly tripping over the audio cable from my
> PC to the TU.Â  Duh.
>
> Anyway, I have no experience with the Raspberry Pi, but this might be a
> good way to get into it.Â  Can you make (or do you already have) your
> project documentation/code available publicly?Â  It sure sounds like a
> neat package.Â  I'd love to try it with my M15 and ST-5000.
>
> Cheers,
> Keith
>
> On Monday, August 26, 2024 at 03:53:43 AM GMT+1, John Spigel
> <w1an.dxusa at gmail.com> wrote:
>
>
> I thought I'd pass on a quick way to access ITTY and other streaming
> audio sources.
>
> I've been developing several Python packages for TTY use on the
> Raspberry Pi. To make my tests across the room to my M15 I've been using
> bluetooth. Yes, the same bluetooth that's on your smartphone. Any audio
> streaming will play well from your phone including the familiar music
> from ITTY. No PC needed.
>
> So what do you need?.. A small bluetooth audio module with a big price
> tag of two for $6.99. If you want 5, that'll be $10.99, please.
>
> Amazon description:
>
> "MakerHawk 2pcs Bluetooth Audio Receiver Board BT 5.0 Stereo Audio
> Amplifier 3.7-5V Car Speaker Amplifier for DIY"
>
> You'll also need a 5V power supply with usb-c connector or cable, if you
> look close you can see solder pads on the device where wires can be
> tacked on. You probably already have a 1/8" audio patch cable and
> adapter to connect to your TU.
>
> Just pair the device with your phone power up your gear and your good to
> go.
>
> OK, Now the projects:
> I wanted to make demonstrations easier with my M15. So I made a portable
> cart with casters to make moving easier. This can be disassembled and go
> in the car. The "TU" is The Deramps Interface. The audio source can be
> either a local Raz Pi, or optionally bluetooth from a phone for ITTY.
> That's a fairly simple setup. No screen necessary. All the devces are
> velcroed to the rear of the cart along with a powerstrip.
>
> The key to all of this is the Python code. The Raz Pi is headless. Three
> miniature, think C&K, ON-OFF-ON switches control up to 27 audio internet
> streams or .pix and .pox image files saved on the PI. The code reads the
> pseudo-binary on the Pi's GPIO pins and selects the source by shell
> scripts for each! When active there is an output GPIO pin for a relay.
>
> Also, I have a Python Text formatter in the worksÂ  the Pi. This is to
> help make text files ready for baudot. It will take mixed text files
> scanned off the internet, news sources, Wikipedia, etc.. I hope to
> eventually use OCR to grab old articles, stories, from archives
> efficiently.
>
> I have: Line length selectable, word wrap with automatic CR/LF
> insertion. Options to Replace LF with Space, LF with CR/LF, a Second CR,
> Letters after Space. Also insertion of a choice of Headers and Footers.
> I'm still trying to break it to see what bugs may develop. I've also got
> it saving the 00011, 01100, etc to a ".5bit" file. That's the best way
> to see the edits along with the text. And I may just use this to run
> GPIO pins.
>
> Another in the works. Raz Pi with "Polar output" on two GPIO pins and
> one GPIO output pin for Autostart when FSK is active. Just add some
> external parts to drive a loop.
>
> Too much to do. So little time. At my age.
>
> 73, John W1AN
>
>
>
>
>
>
>
>
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>>>> Jordan Spencer Cunningham's GreenKeys Search Tool:
>>>> https://teletype.net/gksearch
>>>> 2002-to-present greenkeys archive:
>>>> http://mailman.qth.net/pipermail/greenkeys/
>>>> 1998-to-2001 greenkeys archive:
>>>> http://mailman.qth.net/archive/greenkeys/greenkeys.html
>>>> Randy Guttery's 2001-to-2009 GreenKeys Search Tool:
>>>> http://comcents.com/tty/greenkeyssearch.html
>
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