[GreenKeys] USB to TTY (model15) interface

Mon Feb 13 12:10:08 EST 2023

Part of this has already been done - something like this (without the
unneeded audio step): https://hackaday.io/project/2836/instructions

Take that, set it up to accept serial data and its essentially similar to
the Black Box Cap (I watched ur vid btw), but instead of having an output
serial port, it has output current loop. This may not be perfect or super
clear, however it does work! I tested it with my Model 32, and on the
Battleship NJ where I volunteer this project is chattering a model 15 when
you walk into the message handling compartment using a 12v loop (so I guess
we'll see how long the relays last).

(Interestingly, I'm still curious about the audio part/integration per se
and had put a little thought into it, as I had asked in the past about ToIP
(teletype over IP), and basically a clean RTTY signal streamed to a
minimodem or a device that can basically be this project would not only
work, but in theory, multiplex several/many "sessions" over one audio feed
(however many 170hz streams can jam into 3k audio reliably, but devided by
2, as its only half-duplex/one-way).

My main use case is that I have a detached garage with no ethernet/data
wiring going out there, and it would be cool to have say, 1-2 "virtual
loops" from the house to the garage so stuff in the house can talk to stuff
in the garage.

Jeff

On Mon, Feb 13, 2023 at 10:59 AM W2HX <w2hx at w2hx.com> wrote:

> Ok so I've been thinking about this problem. I wonder about a possible
> solution. The solution I've been thinking about was to create a kind of
> "audio uart." Someone could write some code (would probably have to be
> native windows, native mac and native linux) that creates a stub or virtual
> serial port device driver, like com22 or something. A terminal program on
> the PC (or other PC software that wants to communicate at 45 baud) would
> connect to this com port.
>
> The virtual com port device driver would take the data coming from the
> terminal program and generate AFSK audio tones out the computer's audio
> port. The virtual serial port would allow configuration to determine which
> audio port to use. At this point, a HAL terminal unit (or any terminal
> unit) could be used to either generate RS232 or high voltage loop keying.
> But if someone wanted a dongle that looked more like a USB-serial
> converter, then some Arduino or equivalent thing could be built.
>
> To that end, someone could design a ardunio or equivalent open source
> hardware dongle that takes that audio from the PC and directly creates
> either RS232 serial or a high voltage loop keying (or both). The virtual
> com port software would send the AFSK at 45 baud (or any baud rate you
> wanted) and do things like create the stop bits as desired but as audio
> keying. The com port device driver could have a combination of a large
> buffer and/or x-on/x-off flow control.  Of course data flow in the opposite
> direction would also occur. Serial data going into the hardware dongle
> would be translated to audio tones to go into the PC. The PC's virtual com
> port would translate the audio tones to data for the com port to send to
> the running software. So from a software perspective, this looks like a
> comport and from a hardware perspective, after this open source hardware
> dongle-thingy it looks like the output of a uart at 45 baud (with a loop
> keyer as desired). The whole thing would be like swapping out a UART with,
> lets just call it an Audio UART.
>
> In this way we are not constrained by hardware limitations, we bypass
> these obsolete chips and instead directly generate (or demodulate) audio
> which can be done at any baud rate. Then we have choices how to deal with
> that audio data, either use a TU directly or use some hardware dongle that
> does the audio conversion.
>
> There are some VERY smart  hardware and software people on this list (I am
> not among them) who could probably make this work.
>
> Just my 2c.
>
> 73 Eugene W2HX
> Subscribe to my Youtube Channel: https://www.youtube.com/@w2hx/videos
>
>
>
>
>
>
> -----Original Message-----
> From: greenkeys-bounces at mailman.qth.net <greenkeys-bounces at mailman.qth.net>
> On Behalf Of John Nagle
> Sent: Sunday, February 12, 2023 3:33 PM
> To: greenkeys at mailman.qth.net
> Subject: [GreenKeys] USB to TTY (model15) interface
>
> On 2/12/23 11:55, greenkeys-request at mailman.qth.net wrote:
> > Message: 7
> > Silicon Devices has, however, a development kit where everything is
> > unlocked.? There is also a utility available to set any arbitrary baud
> > rate that is wanted. Note that you have to use the older development
> > kit.? The one with an "N" in it was "improved" in a way that no longer
> > supports 45 baud.? As far as I know, the original kits are still
> > available but I wouldn't expect them to be around forever.? I bought a
> > couple of spares.
> >
> > More information on the device can be found here:
> >
> > https://www.aetherltd.com/connectingusb.html
> >
> > PDW
>
> Yeah, unfortunately the CP2102N will not go down to 45 Baud.
>
> I brought this up with SIlabs, and they put it in a tech note.
>
>
> https://www.silabs.com/documents/public/application-notes/an976-cp2102-3-4-9-to-cp2102n-porting-guide.pdf
>
> In there, SILabs writes:
>
> The CP2102N is feature compatible with the CP2102/9, with two exceptions:
> • Baud Rate Aliasing
> • Line Breaks / Break Conditions
> Baud Rate Aliasing is a feature that allows a device to use a pre-defined
> baud rate in place of a baud rate that is requested by the user.
> For example, a device using Baud Rate Aliasing can be programmed to use a
> baud rate of 45 bps whenever 300 bps is requested.
> Baud Rate Aliasing is not supported on the CP2102N.
> If Baud Rate Aliasing is used in a CP2102/9 design, the CP2102N is
> incompatible as a replacement.
>
> The CP2102 is now listed as "Not for New Designs".
> DigiKey says they still have 44,000 available, though.
>
> It looks like the end of the line for UART hardware which can operate at
> 45 baud. The future is CPU-emulated UARTs, probably.
>
>                                 John Nagle
>
>
>
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