[GreenKeys] Old Dog with some New Tricks.

Harold Hallikainen harold at hallikainen.org
Thu Aug 29 12:06:44 EDT 2024 

Thanks for sharing the info!

Harold
https://w6iwi.org/rtty


On Thu, August 29, 2024 6:45 am, John Spigel wrote:
> Harold, the Pi has some gpio pins suitable for PWM output. These are 12,
> 13, 18 and 19. Square waves would be simpler, but by using these, less
> RC filtering should be needed to approach a sinewave. The math libraries
> running the decoding was written by others much smarter than me. All
> imported. My challenge is finding, getting the right pieces and seeing
> that they play nicely together. There is combination of nyquist,
> butterworth, and configurable high and low pass filters. These two:
> 'numpy' and 'scipy' do much of the math.
>
> The audio player mpg123 and minimodem are your friends and need to be
> installed.
>
> You don't need any programming to get these below to work:
>
> For console/command line access to ITTY outputted in audio, bluetooth,
> etc., I use mpg123. Optional Shell scripts will contain these below.
>
> Here's one that will play an mp3 music file from command line:
> mpg123 /home/w1an/favorite-music.mp3 (Set path to your file)
>
> This will play ITTY off the internet. You get some bug errors but it
> just works. Can't get muche easier.
> mpg123 http://internet-tty.net:8000/ITTY
>
> For image or text files you can use minimodem, written by a ham of
> course. Explains the rtty switch. It is widely configurable.  Here's the
> documents page:
> https://manpages.ubuntu.com/manpages/trusty/man1/minimodem.1.html
>
> The below opens the file and feeds it to minimodem.
>
> cat /home/w1an/Pictures/prettygirl.pix | minimodem --tx -A -M 2125 -S
> 2295 rtty (Set path to your file. Can be a formatted text file)
>
> How's that for easy?
> 73, John W1AN
>
> On 29-Aug-24 00:33, Harold Hallikainen via GreenKeys wrote:
>> 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.  Don't know why I never thought of
>>> using BT
>>> to talk to my TU.  I'm constantly tripping over the audio cable from
>>> my
>>> PC to the TU.  Duh.
>>>
>>> Anyway, I have no experience with the Raspberry Pi, but this might be a
>>> good way to get into it.  Can you make (or do you already have) your
>>> project documentation/code available publicly?  It sure sounds like
>>> a
>>> neat package.  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 works  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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>>
>>
>
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>
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