[GreenKeys] ITTY to real Teletype

[Mike Douglas]

It’s not hard to demodulate the audio in software with an input capture timer on a microcontroller, Arduino, etc.  I’m not familiar enough with the pi hardware to know if it can do the same thing or not. Here are two devices I’ve made that decode FSK audio using software:

  https://deramp.com/model15_interface.html
  https://altairclone.com/cassette.html

If you want to start with either of these pieces of hardware, the Altair cassette interface board would be the easiest to connect directly to gpio pins on a pi. You’d have to write software to monitor the gpio data pin and do a “reverse bit-bang” to receive the 45.5 baud data stream into 5-bit baudot. That could then easily be converted to ASCII and sent to your ASR 33 (assuming you have an RS-232 adapter for your 33).

If your ASR 33 is still connected by current loop, then it might be easier to update firmware in the model 15 interface board to convert the FSK it receives to 110 baud ASCII and drive the 33 directly.

Mike D

> On Oct 6, 2024, at 2:18 AM, Rob Jarratt via GreenKeys <greenkeys at mailman.qth.net> wrote:
> 
> Hello,
> 
> Dave was asking this on my behalf, probably unaware that I am on this list too.
> 
> I have seen mention of ITTY Autostart etc and wondered about receiving all this on my ASR 33.
> 
> My thought was to see if I could set up a Raspberry Pi to receive the audio signal over the internet, translate that to ASCII and then send it to my ASR33. I already have the means to connect my ASR33 from software running on a Raspberry PI or a PC via reverse Telnet. The bit I am missing is what software (if any) there might be that I could run on a Raspberry Pi, or Windows that runs in the background (no GUI) to decode the ITTY audio signal. I am a software developer though, so I guess if such a thing doesn't exist then perhaps I can modify the MMTTY code that is published on GitHub.
> 
> Any pointers would be welcome.
> 
> Thanks
> 
> Rob
> 
>> -----Original Message-----
>> From: greenkeys-bounces at mailman.qth.net <greenkeys-
>> bounces at mailman.qth.net> On Behalf Of Jeffrey Golas
>> Sent: 06 October 2024 05:30
>> To: David Wade <dave.g4ugm at gmail.com>
>> Cc: Mailing List Green Keys <GreenKeys at mailman.qth.net>
>> Subject: Re: [GreenKeys] ITTY to real Teletype
>> 
>> Normally the ITTY service is fed to a piece of hardware called a terminal unit
>> (think modem). The service is streaming as RTTY which is normally sent over
>> amateur radio.
>> 
>> 
>> Jeff
>> 
>>>> On Oct 5, 2024, at 5:34 PM, David Wade <dave.g4ugm at gmail.com> wrote:
>>> 
>>> I know there have been several USB to TTY boards produced, but what
>> software would you use to drive one of these from itty?
>>> 
>>> Dave
>>> 
>>> G4UGM
>>> 
>>> ______________________________________________________________
>>> GreenKeys mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/greenkeys
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:GreenKeys at mailman.qth.net
>>> 
>>>>>> 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
>>> 
>>> This list hosted by: http://www.qsl.net Please help support this email
>>> list: http://www.qsl.net/donate.html Message delivered to
>>> jeffg at junknet.net
>> ______________________________________________________________
>> GreenKeys mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/greenkeys
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:GreenKeys at mailman.qth.net
>> 
>>>>> 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
>> 
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html Message
>> delivered to robert.jarratt at ntlworld.com
> 
> ______________________________________________________________
> GreenKeys mailing list
> Home: http://mailman.qth.net/mailman/listinfo/greenkeys
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:GreenKeys at mailman.qth.net
> 
>>>> 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
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to deramp5113 at yahoo.com
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/greenkeys/attachments/20241006/d8b3bb98/attachment.html>