[Ovmsdev] Crashes with streaming mode

[Mark Webb-Johnson]

Michael,

Looking at the design for 3G modules, I noticed something recommended for those modules that seems to be supported for the SIM900 base we use (both SIM900 OVMS v1 and SIM908 OVMS v2). CMUX mode.

http://www.m2m-platforms.com/seminars/2007seminar_material/Telit_CMUX_2_M2M_Platforms_seminar_2007.pdf

This is GSM 7.10 TE-MS multiplexor protocol.

The main problem we have is co-ordinating all the different comms channels of OVMS onto a single serial link to the modem. Incoming SMSes, status indicators, outgoing GPRS TCP data, etc, all run over each other.

The CMUX protocol appears to allow us to have 3 (or 4?) virtual async links, over a single physical async port. We could use one for SMS, another for TCP, and a third for GPS polling. The 3G modules even allow the GPS NMEA data to be streamed back over one of the virtual ports (but I don't think that is available in the SIM908 module we use - hard to tell as the CMUX documents focus on SIM900 not SIM908 [the SIM908 embeds SIM900 and adds GPS]).

It would mean some major restructuring of the comms layer (NET), and we would have to build a small library to encode/decode GSM 7.10, but may be a much more stable approach in the long-term.

SIMCOM seem to implement a subset of the full GSM 7.10 functionality. Here's the manual on it for SIM900:

http://www.mt-system.ru/sites/default/files/sim900_multiplexer_user_manual_application_note_v1.3.pdf



Regards, Mark.

On 29 Apr, 2013, at 11:48 PM, Michael Balzer wrote:

> Am 28.04.2013 17:06, schrieb Michael Balzer:
>> I just checked in my fix for the USSD reply handler. My tests with streaming enabled did not produce any more crashes, so I think that was the problem.
> 
> I was wrong, it's still crashing. I have to dig deeper it seems.
> 
> Has anyone observed crashes with streaming mode on other vehicles, or is this a Twizy specific bug now?
> 
> Thanks,
> Michael
> 
> -- 
> Michael Balzer * Paradestr. 8 * D-42107 Wuppertal
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