[GreenKeys] Nagle's teletype board key part nearing end of life

[Michael Katzmann]

FYI I've been working with the maintainer of the Linux USB serial driver to
fix the Prolific PL2303 driver for arbitrary baud rates.
These are pretty common and inexpensive USB to serial devices.
All the versions of the 2303 will work at arbitrary rates but because the
chip divider algorithm changed with the TA and TB versions, the current
Linux driver did not work for non standard rates.
The patch I worked on fixes the problem. It will roll into the mainstream
kernel soon.
https://git.kernel.org/pub/scm/linux/kernel/git/johan/usb-serial.git/commit/?h=usb-next
If any needs the updated driver now, drop me a line. You can use "dkms" to
replace the current one pretty easily.
It does work at 110Bd and 45 Bd  (the chip will do 45.465 but Linux doesn't
handle fractional rates 8-)

Michael


On Sat, Mar 27, 2021 at 5:59 PM John Nagle <nagle at animats.com> wrote:

> My USD to serial board, described here:
>
> https://github.com/John-Nagle/ttyloopdriver
>
> uses the SiLab CP2102 USB to serial port part.
>
> As of March 2021, the SiLabs CP2102 USB to serial part is "not
> recommended for new designs". The "drop in replacement" CP2012N will not
> work. It will not run at speeds below 300 baud.
>
>  From SiLabs' porting guide: "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."
>
> Ref:
>
> https://www.silabs.com/documents/public/application-notes/an976-cp2102-3-4-9-to-cp2102n-porting-guide.pdf
>
> It's become difficult to find serial devices that will run at 45 baud.
> The CP2102 was one of the last. It's still available, so if you plan
> to build that board, stock up now.
>
>                                 John Nagle
>
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