Voice Calls using EM7565


We are in the process of replacing some obsolete Quectel UC20 modules with EM7565s. These will solely be used to make and receive voice calls and possibly SMS.

Our Linux application interacts at our low level with the Quectel using:

  • AT strings via a file descriptor opened from /dev/ttyUSB2
  • 16 bit PCM audio data via a file descriptor opened from /dev/ttyUSB1

Both file descriptors (using event handles) are added to poll() to receive events from the Quectel module.

My questions are:

  1. Can the EM7565 be used in this low level way without any Gobi drivers via ttyUSBx?

  2. If not, which API/interface would be recommended to implement simple voice calls? The full API looks overkill but the lite-API appears to support funcctions to esablish and receive calls.

  3. How does the audio data work when using the GobiNet Ethernet interface? During a voice call, what format is the audio data and how is it addressed?

you might try with qcserial to enumerate the USB serial port, but I am not sure if it works or not as it is not come from SWI.

I don’t think the module is supporting voice as there is no audio PCM/I2S hardware interface

Thanks, I’ve some follow on questions:

  1. When you refer to no voice support, I assume thatiin this mode t only acts as a LTE data interface providing internet access?

  2. WWith reference to my first question, how does the EM7565 process a dial command e.g. ATDxxx or voice_SLQSVoiceDialCall() from teh liteAPI, sand pecifically wow tis eh audio path iandled?

  3. Which Sierra Wireless LTE module would support voice calls where a PCM audio path wouldd be available to connect to?

  1. Yes, lte data only
  2. I guess error will be returned
  3. You can try wp76 module


I can confirm the EM7565 (or any of the MC/EM products) does not support voice, it is certified for data only.