Re: [Gumstix-users] GSMstix Preview

[MadAlexGumstix <Gum...@ma...>]

On Wed, 02 May 2007 18:16:16 -0700, "Gordon Kruberg"
<go...@gu...> said:
>
> Thanks for all the feedback.  I just updated the test version's
> information to:
>
> <http://pubs.gumstix.com/boards/GSMSTIX/PCB00014-R1502/>
>
> Lots of great feedback-- thanks very much.  A few key points about
> this version.
>
> 1) We are still evaluating how to connect to the GPS and GSM over the
>    UART.  We are leaning towards using a switch that would allow
>    multiplexing and use just the stuart for this.  This leaves the
>    btuart open for the bt module on the verdex if it's so used.

Given the expected desire to preserve "traditional" GPS serial port
access, will a mux'd serial port "play well with others" when shared
between the GPS and GSM modules?

 - Same default port settings for both GPS and GSM?
   - Special init script(s) required to setup/select "default" device

 - Is the serial port required/desirable for the GSM?
   - Command/control/status? SMS?

The NEO-4S also supports USB connectivity. If the serial port is mux'd,
could the USB be connected? Note that some folks on the gpsd-dev mailing
list have been trading info about u-blox GPS modules' USB I/O - the
modules they've been testing appear to have a USB-serial bridge chip
built in that shows up as a COM port on Windows and Mac PCs.


> 2) Given the above (i.e. get us your feedback) we did not switch to
>    3.0V logic for the GPS module. It's a good idea

Well, assuming you have the space for a SOT23-8 or TDFN-8, you _could_
put a dual, bi-directional level translator between your serial port mux
circuit and the GPS module - e.g. a Maxim MAX3372E, MAX3373E, 3394E or
MAX13014 for ~ $1.00 ea in quantity.

;)

<http://para.maxim-ic.com/cache/en/results/5043.html>