SIM5320 CMUX problem, Having problem implementing multiplexer with SIM5320 Опции

[bernarduh]

Hello.

I'm prototyping a board that uses a SIM5320. Currently i have a prototype that is working with the uart interface without multiplexer.

My next and crucial step is to get the uart interface to use the multiplexer function so that i can have 3G/GPRS and GPS at the same time.

The module is connected through a null modem connection (RTX -> TXD/ TXD -> RXD).

To implement the 07.10 Multiplexer protocol i'm using the Linux kernel driver n_gsm. Currently i have already modified this driver in order to get some comunications out of the SIM5320 in CMUX mode.
I'm able to establish the DLC0 but after that the only thing that the SIM5320 sends is sequences of F9 F9 F9 F9. After a lot of digging i found out that the module can send this flags in a few situations:

Indicate the connection is established.
Module has wake up from sleep mode.
Module is out of sync and is discarding the frames until i send it F9 F9 F9 F9.

I already tried to send it back the F9 F9 F9 F9 but the module send them back :s.

ATI

Manufacturer: SIMCOM INCORPORATED
Model: SIMCOM_SIM5320E
Revision: SIM5320E_V1.5
IMEI: 861311000924364
+GCAP: +CGSM,+DS,+ES

OK

Currently this is the only issue stopping me from sending the board for PCB production so this is kind of urgent.
I'm really need help on this topic.

Thank you for your attention.

Sorry for posting in English but i Portuguese and can't speak Russian.