Re: ZTE modem problems and workrounds

[Dan Williams <dcbw redhat com>]

On Wed, 2009-07-01 at 19:33 +0100, Rick Jones wrote:
> --On Wednesday, July 01, 2009 08:11:51 -0400 Dan Williams
> <dcbw redhat com> wrote:
> > Ok, we need to figure out what commands it actually responds to, and
> see
> > if there's some way to distinguish the specific ports.  Are you able
> to
> > get a program like minicom or screen running on the ports so we can
> try
> > out some commands.  If you can do that, try the following commands
> on
> > all the ports the modem exposes, and let me know what they return
> > (including what port you entered it on):
> > 
> > ATI
> > AT+CGMM
> > AT+CGAP?
> 
> Using minicom, both ports give identical responses to all these:
> ATI:
> Manufacturer: ZTE INCORPORATED
> Model: MF627
> Revision: BD_3GHAP673A4V1.0.0B02
> IMEI: 358066024082082
> +GCAP: +CGSM,+DS,+ES
> 
> AT+CGMM:
> MF627
> 
> AT+CGAP? is ERROR, or did you mean AT+GCAP:
> +GCAP: +CGSM,+DS,+ES
> (same as last line of ATI response).
> 
> Functionality is definitely tied to the IF number. IF0 is effectively
> dead (supposedly NMEA, but I don't know what it's meant to support).
> IF1 & IF3 both behave like a modem (usually), and seem very closely
> tied together. E.g. if you use ATE0 to turn off echo on one port, it
> is turned off on both. Very occasionally, IF1 will not respond to AT
> commands, but the modem still works on the correct IF3 port, and IF1
> still spits out messages.

How often does IF1 spit out messages?  What do they look like?

Dan

> UMs always come out together on both ports (except when IF3 is
> connected of course).
> 
> I haven't tried every possible AT command, but AFAICS from those I
> have tried, they all work the same on both ports, EXCEPT for dialling.
> A valid ATDT string on IF3 produices an immediate CONNECTED response,
> but on IF1 there is no response, and the port hangs. This also
> effectively crashes the device, because once you disconnect from the
> ports the device shuts down and all the ttyUSB nodes disappear.
> 
> I kinda wonder if the device is actually really buggy and IF1 is not
> supposed to accept commands at all.
> 
> I can't see any way to detect the difference between the ports
> heuristically, it seems to need hard-coded knowledge of IF3. I started
> using it on an earlier OS, Ubuntu 8.10 (Hardy), and that required
> addition of a custom fdi file that explicitly identified IF3 as a GSM
> modem, and it always used the correct port. I can't remember exactly
> what kernel version that was.
> 
> Now with 2.6.29 that file isn't necessary, and there doesn't seem to
> be any reference to the device in the standard fdi files, so the
> mechanism is different, but I don't quite understand how. Maybe it's
> because Hardy used NM 0.7.0 ?
> 
> It would be good to be able to use HAL or similar to explicitly
> declare the interface, or even declare IF1 as non-available just to
> stop it being probed. Is that possible?
> 
> > Second, do any of the non-usable ports spontaneously emit messages?
> > Huawei devices emit a variety of AT^BOOT, AT^RSSI, etc on the
> secondary
> > port that can't be used for PPP, and that's something we can detect.
> 
> To confirm what I said above, all the spontaneous UMs are identical on
> both ports, so not muc help there :(
> 
> Not sure where this gets us ...
> 
> -- 
> Cheers
> Rick