EC25-E EFAR – USB Audio/UAC not detected and no call audio – Firmware request

Technical Subjects Driver
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1

Hello

I am using a GSM voice gateway containing 8 Quectel EC25-E modules. I need to use the USB Audio Class (UAC) interface to transfer GSM call audio between the EC25-E and a Windows PC, including both microphone input and speaker/output audio.

Module information:
EC25-E
Revision: EC25EFAR08A06M4G
Firmware: EC25EFAR08A06M4G_20.201.20.201
USB VID/PID: 2C7C:0125

Current USB configuration:

AT+QCFG=“usbcfg”
+QCFG: “usbcfg”,0x2C7C,0x0125,1,1,1,1,1,0,1
OK

UAC activation:

AT+QPCMV=1,2
OK

AT+QPCMV?
+QPCMV: 1,2
OK

The GSM voice call itself works correctly with ATD/ATA/ATH and the call is successfully established.

However, there is NO audio in either direction. I cannot hear the remote party and I cannot send microphone audio.

There is also no physical audio connector, speaker or microphone on my gateway. Therefore, I need the call audio to be transferred through USB UAC to the Windows PC.

The main problem is that Windows does not detect any USB Audio/UAC device from the EC25-E. Nothing appears under:

  • Sound, video and game controllers
  • Audio inputs and outputs

Only the USB serial interfaces are detected, for example:
USB Serial Device (COM6)

I also explicitly reapplied the USB configuration:

AT+QCFG=“USBCFG”,0x2C7C,0x0125,1,1,1,1,1,0,1
OK

AT+QPCMV=1,2
OK

AT+QPCMV?
+QPCMV: 1,2
OK

Even during an active voice call, no USB Audio device appears in Windows and there is no usable audio path.

After reboot, QPCMV returns to:
+QPCMV: 0,0
which I understand may be normal because QPCMV=1,2 must be enabled again after boot.

Could you please confirm whether firmware EC25EFAR08A06M4G_20.201.20.201 has any known USB UAC/audio limitation or bug?

If possible, please provide the latest recommended firmware for EC25-E EFAR that fully supports USB Audio/UAC for voice calls, together with the appropriate flashing tool and instructions.

Please confirm that the firmware is compatible with:
EC25-E / EC25EFAR08A06M4G
VID: 2C7C
PID: 0125

I have 8 identical EC25-E modules in the gateway, so I would like to test the firmware on one module first and then update the other 7 if the UAC/audio issue is resolved.

Thank you for your support.

2

Hi mate,

Thanks for the detailed information.

Based on the configuration provided, the AT+QCFG="usbcfg" setting is correct and AT+QPCMV=1,2 is being accepted.

Please note that usbcfg requires a module reboot/power cycle before the USB interface configuration takes effect, while QPCMV=1,2 needs to be enabled again after each reboot.

We recommend the following sequence:

  1. Set AT+QCFG="usbcfg",0x2C7C,0x0125,1,1,1,1,1,0,1
  2. Reboot the module using AT+CFUN=1,1 or power cycle.
  3. After reboot, execute AT+QPCMV=1,2.
  4. Check Windows Device Manager for the USB Audio/UAC interface.

AT+QDAI is not required for USB audio, as it is intended for the physical PCM audio interface.

I have also sent you the latest firmware via email. Please check your email and use it for testing.