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