[Gta04-owner] Using a GTA04 of as wifi hot-spot.

NeilBrown neilb at suse.de
Thu Jan 3 01:49:23 CET 2013

I've been away from home during the summer holidays and ended up using my
GTA04 to provide Internet access for the family.
It wasn't perfect, but still more reliable than the 3G USB stick I bought and
intended to use (with Win7 it didn't really work reliably at all, with Linux
and the very latest drivers it worked OK but needed to be reset every few

The wifi in the GTA04 doesn't support access-point mode but I have a little
plug-pack wifi access point so I used that to provide the access point
functionality and to forward packets between various note books and the GTA04.

 - Using wifi and 3G-internet uses more than 500mA, so the battery slowly
   went flat even while plugged in to a normal USB charger.
   When I plugged in my Freerunner charger, which the GTA04 recognises as
   such and draws 800mA from, the battery didn't go flat, and even charged

 - The wifi driver very occasionally locks up.  Maybe once every 2 days it
   would stop working and the evidence strongly suggests wifi as the problem.
   I didn't get any good stack traces but it would be something worth
   experimenting with - run wifi heavily for hours on end and see what

 - The 3G modem would sometimes get into a confused state and stop working.
   The symptoms were:
   (which tries to establish a data call) would result in AT_OWANCALL? (Which
   gets the current status of the call) reporting 
     _OWANCALL: 1, 3
   where the '3' means "Call setup failed".
   Also "AT+CSQ" would get "+CSQ: 0, 99" - i.e. no signal.
   and "AT+CFUN?" would get "+CFUN: 6" - I couldn't find the '6' documented
   When this happened an "AT_ORESET" and then reopen the ports would normally
   get it working again.  Sometimes the modem wouldn't re-appear on the USB
   and I would need to power-cycle.

 - AT_OWANCALL=1,1,1
   should result in asynchronous notification of call status. (The last '1'
   means async notify).  However that notification only ever appears on 
   /dev/ttyHS_Control, much like the 'NO CARRIER' when the remote end hangs
   up only appears on /dev/ttyHS_Modem.
   As I didn't want to use HS_Control in my main modem monitoring app (I
   leave that free to send SMS messages) I just used polling with AT_OWANCALL?
   to get the status.

So: not entirely trouble free, but very educational and I got it working
reasonably well.

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