[GreenKeys] USB to Loop TTY Control Device

[eric]

Like this?

https://www.heepy.net/index.php/USB-teletype

I'm sure there are still some floating around, between Jordan and myself 
we probably built 150 or more of them. I probably still have a couple 
available.    I do think you would be hard pressed even in 2024 to build 
it for $5 in materials, though.

I don't mean to suggest there isn't room for a newer design, but I think 
if someone were to do that it would make sense to *really* update it, 
for instance with USB-C, WiFi, tcp/ip connectivity, maybe onboard FSK 
en/decoding, etc.  MCUs are powerful now.

eric

On 2024-03-13 17:17, ad7i wrote:

> Greeting Greenkeyers --
> 
> I've been reading on this group about the discontinued manufacture and 
> availability of USB to SERIAL (bridge) devices that can run 5 bit 45 
> baud data on the serial side.
> 
> I can't offer any alternative device suggestions that can do that 
> USB-SERIAL bridge function natively like the older devices do, but I 
> wanted to ask the group if anyone had an interest in a device that 
> would accept USB Serial ASCII and the output would be a loop control 
> switch (like an opto-coupler) that would key a loop with 5 unit TTY 
> code, as controlled by the host PC?  It would be also possible for the 
> host computer to send 5 unit code to the TTY by putting the device in 
> mode where it only looks at the lowest 5 bits of the incoming ASCII 
> code and then sends that 5 unit code to the TTY (which moves the 
> responsibility of coding of FIGS and LTRS from the device to the host 
> computer).  That type of functionality would *not* be compatible with 
> existing PC or Linux code that drives one of the older USB-SERIAL 
> devices that can run a 45 bps.  But if you had access to the source 
> code it should be a straightforward task to modify that code to use the 
> device I describe to drive a 5 unit TTY.  Control of the device (change 
> mode from ASCII to BAUDOT or BAUDOT to ASCII, set bit rate (45, 50, 75, 
> 100), disable/enable loop control inversion, etc. would be done through 
> something like an escape character followed by two letters or numbers.  
> I'd propose to use the ASCII caret symbol (^,  0x5E) as the escape 
> character.   So to set the loop baud rate to 45.45 bps the host 
> computer would send ^45 (which would not print on the TTY).  To set the 
> code to BAUDOT the host computer would send ^BA (which would not print 
> on the TTY), etc.  The particular escape character and the two 
> character command that followed could be most anything, as long the 
> escape character is not a symbol that a TTY would print.  The device 
> could also include functionality to send data from the TTY Keyboad loop 
> to the host PC.
> 
> I think something like this device could be constructed for less than 
> $5 in parts, including the PCB.  Power would be supplied to the device 
> from the Host computer via the USB cable.
> 
> If this might be of interest to you please let me know and we can kick 
> around the specifics of functionality and specifications.
> 
> 73, Paul, ad7i
> ad7i at ad7i.net
> Middletown, NJ
> 
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