GSM 0710 Multiplexing

[dgotfroi]

Hello,

I use an IMX28 to communicate with a GPRS modem SIM900.

I would like to be able to send AT commands during data session (ppp), so I intend to use the GSM 0710 standard to multiplex the serial port.

I think the option to check in the kernel menuconfig is "GSM MUX line discipline support", isn't it ?

But after the compilation, how can I multiplex my serial port on my board ? What are the commands to enter?

I use Yocto + bitbake with kernel 3.12.

Many thanks and best regards.

[alejandrolozan1]

Hi,

Do you want to configure the pin configuration in runtime?

Or you just need to configure those pins for UART? If so, the configuration needs to be done in the .dts file.

You can find that file in the linux source code. There you can find a very good example for the pins you need.

At runtime, I believe there is no an API that changes the pin configuration, you will have to implement it.

Best Regards,

Alejandro

[dgotfroi]

Excuse me but can you tell me where I can find the example for multiplex UART ?

I search in .../git/documentation but I didn't find anything about UART multiplexing.

Many thanks

[alejandrolozan1]

Hi,

The dts that you can use as rerence is found at tmp/work/imx6sxsabresd-poky-linux-gnueabi/linux-imx/3.10.31-r0/git/arch/arm/boot/dtstmp/work/imx6sxsabresd-poky-linux-gnueabi/linux-imx/3.10.31-r0/git/arch/arm/boot/dts.

This file contains the description of the devices and pin configurations you need to modify.

Remember that this configuration is performed at the very beginning of Linux boot up.

Best Regards,

Alejandro

[dgotfroi]

I think there is a misunderstand.

I don't want to configure a GPIO as an AUART instead of SSP (for example), what we do in the dts.

But I would like to multiplex AUART 1 (so /dev/ttyAPP1) with GSM 0710 MUX protocol in order to have 2 virtual COM port (/dev/ttyAPP1a and /dev/ttyAPP1b).

It is often used with GSM which has only one serial interface. You can multiplex this serial port following the GSM 0710 MUX protocol to have, together, a data connection (ppp) and a command connection (AT command).

I found "GSM MUX line discipline support" option in kernel menuconfig but I didn't find how to use it.

I work with an IMX283 and I use Yocto + bitbake with kernel 3.12.

Many thanks for your help

[dgotfroi]

Hello.

Thanks for your answer.

I need to enable 0710 GSM Multiplex for one specific AUART.

I will try to find this example.

Many thanks

[jamesbone]

alejandrolozano, Can you please check this ?