ttyUSB2 to run 3G and AT commands at the same time


ttyUSB2 port is used for both 3G/4G and AT commands. When we use 3G/4G, ttyUSB2 is locked and we can't send AT commands to the mounted 3G/4G device. Vice versa, when we can send AT command, we can not use 3G/4G.

Is there any solution to use both 3G/4G and AT commands at the same time for port ttyUSB2?

Can anyone help?

Thank you in advance.


Which modem? Which driver(s)? Is usb-modeswitch installed?

Typically, one either uses AT commands or QMI (or similar) protocol on a single port. Some device drivers create multiple serial ports, one for each supported protocol (and possibly GPS data).

I am using ZBT826 working with MC7455.
Yes, I need to send AT command to get GPS data, but it seems I can only use ttyUSB2 for only one service at a time 3G/4G or AT command.

Yes, I have installed usb-modeswitch

I have tried to remove the lock file in /var/lock/LCK..ttyUSB2, but it wasnot working yet.

Can you give me a solution?

See if the forum search will give you some useful information:


I can't find any solution from the link you sent.

Please anyone has any idea?

Thank you,


is there anyway to configure AT command on another port?


Try to use cmux with activated n_gsm option in kernel. It's create 4 multiplexed at ports

1 Like

Hi Tony ,
i am facing same problem actually i am huawei E3276s modem it gives two port /dev/ttyUSB2 and /dev/ttyUSB3 when i am connecting 3g mode ttyUSB2 not working but at sometime ttyUSB3 work to send msg but it also add some garbage value and sometime skip some msg body content.if you solve this problem please.................................... guide me if you any idea about it please share with me or if any one solve this issue please help me.

Thank you