[GreenKeys] Support for serial ports

[John Nagle]

> Sherry Guttery wrote:
>> >  On 6/15/2011 4:00 PM, Chris Elmquist wrote:
>>> >  >I took a slightly different approach to this problem--  which was to put
>>> >  >a small microcontroller (Atmel ATTiny2313) between the upstream serial
>>> >  >port and the TTY.
>>> >  >
>>> >  >
>> >  An elegant solution for sure - but come on Chris, not everyone has
>> >  your talents and skill at making such...  While the CP2102EK does
>> >  require some minor programing (it comes with the program and docs to
>> >  do so) - it requires no hardware assembly nor programming skills...
>> >
>> >  just my .02...
> I didn't mean to imply that this was_THE_  solution... just another.
>
> _My_  experience with USB to serial converters has been poor.  Unless you
> build your own board with one on it, and choose the chip yourself,
> you will probably be playing roulette with which device you actually
> end up with inside an over-the-counter dongle.  That process for me has
> been non-deterministic.
>
> Device driver support for them is also chaotic...  with random behavior
> appearing for things like flow control, speed selection, buffer
> management, etc.
>
> So, I chose to solve the problem in a different part of the chain...
> and I also wanted to connect to legacy serial ports on things like
> terminal servers and old mini-computers where there is no place to plug
> a USB to serial converter.
>
> Chris N0JCF

    There are lots of ways to do this.  I chose the CP2102EK because
1) it's an evaluation board for an IC, with full engineering 
documentation, 2) it's not too expensive, and 3) I had to write a host
side application to drive the Teletype anyway, and splitting the job
between that and custom code in a microcontroller didn't seem
worthwhile.

    The part of my system that gets SMS messages from a phone out on
a Teletype is far too complex, though.  (At steampunk conventions,
we set up a whole Aetheric Mesage Machine Company telegraph office,
with costumed operators and messengers, multiple Teletype machines,
and antique office equipment.  Messages come in from attendees'
cell phones and printed on our Model 15 with a brass and glass case,
stamped and sorted by operators, and delivered around the convention
by messengers. It gets very busy.)

    This works reliably, but has too many parts. I have an account
with Twilio, an SMS gateway to receive SMS messages.  Twilio
then makes a request of a program I have on one of my web sites.
That program checks the message for format and replies via SMS to
the caller, then puts the message in a MySQL database.  Back at
the Teletype, I have a EeePC 2G Surf subnotbook running a Python
program polling my web site every 5 seconds for traffic.  When it
gets a message, it prints it, then notifies the server that printing
is complete.

    When I ran this at the Nova Albion steampunk convention last March,
we had serious problems connecting to the hotel's WiFi network, which
didn't reach into the function rooms.  I had to run out and buy a WiFi
booster to get connectivity.  For the next convention, I'll probably
get a Virgin Mobile WiFi mobile hotspot with the $10 for 10 days plan,
as a back up in case WiFi is being difficult.

    I really should move all that back end machinery into a smartphone
app, have the phone talk to the Teletype through a USB port,
and get up to date.


				John Nagle