[GreenKeys] Old Dog with some New Tricks.

Harold Hallikainen harold at w6iwi.org
Thu Aug 29 12:08:27 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:
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>>>>>> 1998-to-2001 greenkeys archive:
>>>>>> http://mailman.qth.net/archive/greenkeys/greenkeys.html
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>>>>>> http://comcents.com/tty/greenkeyssearch.html
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>>
>>
>
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>>>> 1998-to-2001 greenkeys archive:
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>>>> http://comcents.com/tty/greenkeyssearch.html
>
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