# Serial communication with Sierra Wireless EM9291

Source: https://forum.modalai.com/topic/3192/serial-communication-with-sierra-wireless-em9291
Category: ESCs, Sensors and Accessories (https://forum.modalai.com/category/15/escs-sensors-and-accessories)
Tags: cellular
Posted: 2024-03-11 06:42:54 UTC by schew
Replies: 7 · Views: 2907

## schew · 2024-03-11 06:42:54 UTC

Hi,

I am using a Sierra Wireless EM9291 modem with VOXL 2 and the carrier board, which I want to connect to over serial to send AT commands. 

I cannot find the device path in /dev, ls /dev/ttyUSB* returns no such file or directory. How should I communicate with the modem?

## Reply by Alex Kushleyev (ModalAI staff) · 2024-03-13 02:46:02 UTC

@schew, hello, have you tried setting up our standard software using `voxl-configure-modem` , following this documentation page https://docs.modalai.com/5G-Modem-user-guide/ ? That would be a good first test.

## Reply by Eric Katzfey (ModalAI staff) · 2024-03-13 15:40:03 UTC

@schew Why do you need to send AT commands to the modem? What are you trying to do with the AT commands?

## Reply by schew · 2024-03-15 04:54:01 UTC

I have configured the standard software with voxl-configure-modem; it works and I can connect to the internet, however the APN is different as I am not based in the US.
I am planning to use the AT commands to configure some of the more specific parameters of the modem e.g. setting bands, etc.

## Reply by Eric Katzfey (ModalAI staff) · 2024-03-15 15:30:40 UTC (in reply to schew)

@schew There are some scripts in our `voxl-modem` repo that use AT commands. https://gitlab.com/voxl-public/voxl-sdk/utilities/voxl-modem/-/tree/master/scripts?ref_type=heads

## Reply by hmlow · 2024-06-01 10:52:49 UTC (in reply to Eric Katzfey)

@Eric-Katzfey 

Did anyone manage to send AT commands to the EM9291?
Doesnt seem to be possible as no virutal serial ports ttyUSB* were created.

While it is possible to use qmicli --nas-xxxx functions to set and query information, it is no where near the flexibility offered by AT commands.
For instance, i may wish to lock preferred network to LTE instead of 5G/LTE to prevent it from switching back and forth.

## Reply by groupo · 2024-06-13 19:10:50 UTC (in reply to Alex Kushleyev)

@Alex-Kushleyev  Hey going off of this... I also have an EM9291, and the forums say "The user will be prompted to select their modem hardware". When running voxl-configure-modem, of the 7 options presented, none seem to be appropriate for my em9291. Is option 7) em9191 a typo? Or should I be using another option? If more appropriate to make a separate post, please let me know and I will.

## Reply by tom (ModalAI staff) · 2024-06-13 19:20:19 UTC (in reply to groupo)

@groupo em9191 should work for you