EC25-au (brazil) LTE not sucess call over LTE (VoLTE)

Dear Sir,
How about your VOLTE test now ? Whether you can make a VOLTE call successful ?
Just as you have said that you have update the MBN file successful which can support TIM Brasil, then you can follow up the test step that we provided to have a try. If still failed, please provided your test AT log and also the debug log. We will help to debug it. Thanks!
By the way, you also can contact our local FAE or send email to to get support on site. Thanks!

Hi yes i have (i need update for more other operators , claro , vivo , oi , and more ) .

In this moment i try using virtual interface audio “AT+QPCMV=1,2” , but i have issues with mic .

I try create my code to fix this , but in this moment is in alpha my code.

Dear Carlos,
Could you tell me why you will use the command AT+QPCMV, which is different application from VOLTE, right ?
As we know that AT+QPCMV is used to enable to transfer PCM Data via USB or UART Port. Thanks!
And about your issue with MIC, could you share more information with me, then we will try to help you to solve it. Thanks!

Frist :

Second :

Tree : ( Quectel_EC2x&EG9x_Voice_Over_USB_and_UAC_Application_Note_V1.0.pdf )

For this i have problem with mic.

Dear Carlos,
Could you describe your issue in detail ? As you know that Voice over USB and UAC are different, and they are all verified.
If you test Voice over USB function, you can try to follow up the following steps to have a try. Thanks!

  1. AT+QGPSCFG=“outport”,“none”
  2. AT+QPCMV=1,0
  4. ATD dials a call or ATA accept the incoming call on the USB AT port.
  5. PCM application on the device will receive 640 bytes of PCM data through USB NMEA port in every 40ms, and process the received data immediately (broadcast or save).
  6. PCM application on the device will obtain MIC recording data through audio process unite. It is required that the PCM application should send 1600 bytes of voice data to USN NMEA port at an interval of 100ms.
  7. Execute ATH command to hang up the phone on the USB AT port or the opposite side hangs up the call, and USB NMEA port will stop outputting PCM data.
  8. Execute AT+QPCMV=0 to disable Voice over USB functionality on the USB AT port.

Yes i know , in frist moment i try use my application to use ec25 UAC , over “alsa/pulseaudio” .

My other code for use with python to create a dashboard for calls , i use USB NMEA , this is next change i need in my code , but in this case is more complex , to create from scratch.

Thanks share specs for use port USB NMEA , you gave me more information than I had separated , big thanks .

After i have success , i share my project over licence GPL in github and in this page too .

Dear Carlos,
Thanks, we will waiting for your news. Any help you need, please do not hesitate to contact us. Thanks!

My code for reference :
Is not finished , but is probable work partial

Thanks for your sharing. Thanks!

Hi i test with my software, i receive audio, but my mic is not send to other side.
I test with windows and have same problem with Qnavigator_V1.6.9.1.

Is there any other parameter that I may have missed?

Dear Carlos,
If you can receive the audio, the module uplink is normal, and about your MIC, it is better to check whether the hardware design have any problem.
And the module have no any other special parameters setting, you can check the following document. Thanks!
Quectel_WCDMA&LTE_Audio_Design_Note_V1.2_20170723.pdf (1.5 MB)

I understand that I must check my hardware.

My question is if the modem supports audio on both sides and if so, what configuration do I need to adjust by serial AT command, to activate the sound on both sides of the connection.

Edit :

I Read this pdf (big thanks) , and i found this sequence :


I not sure if is this option i need configure to receive both side (with NMEA ou UAC) , is possible inform if is this i need to receive both side ? (for me I haven’t fully understood it yet.)

Dear Carlos,
Yes, the module can support audio on both sides. Normally, you do not need to set any special parameters, just need to pay attention to use the right audio path like handset or speaker, of course you should need to connect the external codec chip set. Just the above need to be noted. Thanks!


NB: I have posted the same question here which I hope is OK: /asterisk-volte-support/5232)

Hello Carlos, Kyson,

If this was resolved please could the solution be summarised and published here.

If possible I wish to achieve the following:

Summary: Analog phone FXS calls over VoLTE with Quectel EC25, EP06 and >Cat6 modems

Equipment Bill of Materials

Is this feasible and likely to be successful?

I look forward to hearing from you.

Many thanks,

so the problem is which one is the audio path
ttyUSB0-4, which one

hi, carlos
I am also using asterisk with freepbx on my raspberrypi for a few years, but my USB dongles are from Huawei and all of them are 3G/2G mode. They are working well on CS.
You know GSM/wcdma is getting old, some countries have stopped 2g, this is the reason why i want to change them to VoLTE
I know VoLTE is supported on quectel ec25/ec20, but using on asterisk-chan-dongle, it shows “voice support NO”

*CLI> dongle show device state dongle0
-------------- Status -------------
Device : dongle0
State : Free
Audio : /dev/ttyUSB1
Data : /dev/ttyUSB2
Voice : No
SMS : Yes
Manufacturer : Quectel
Model : EC20F

If you have any update, just write here

Dear Copperfiled,
Please check the following picture which show that ttyUSB0 is DM port that used for catch module debug log and upgrading firmware. What i mean the audio path is not the module USB port, is the path like handset or speaker. Thanks!

It means Audio goes to ttyUSB1

Yes, correct. Thanks!

Good morning from Brazil.

The success I had was just receiving the audio from the person who i talking , but the uploading of sound from my microphone, did not work, through the serial interface.

I am studying how to make the dialing code in python to test 100% both sides of the call sound through the usb interface, if you want to talk, call me on telegram @Casantoslopes.