EG91 and the NAU8810 codec issue


We integrated in our solution the Quectel EG91-EX and the NAU8810 codec.

They work correctly in almost all cases but in order to test our production process, one of the test we must to do is to activate the loopback (AT+QAUDLOOP=1) that seems not to work.

We made the test with a sinusoidal signal generator at 1Khz frequency and 200mV. This signal is get into the microphone input of the codec. If loopback is enabled, the signal it’s going to come out through the speakers and we can measure it with an external instrumentation.

We did this test in past with other Quectel modems that have analog audio, like the M66 without any problems. Also using audio gain commands like AT+CLVL to ensure desired amplitude.

But in the case of EG91-EX and NAU8810 we couldn’t get this test to work even if we know that the microphone and speakers works properly, since we have tested it in a voice call.

Can you help us to understand the issue?

Many thanks

Hello jogagua, thanks for your question
When performing the LOOP test, you need to make sure that the correct CODEC is configured. You can use the AT+QDAI? command to query the audio interface configuration. Your CODEC is NAU8810, then you can change the value to 2. Then you need to configure AT+QSIDET to set the sidetone gain in the current mode. In different audio modes, the default value may be different, so you need to set it (the larger the value, the more obvious the test effect). You can follow the steps below:

  1. AT+QDAI configures digital audio interface (restart after setting)
  2. AT + QAUDLOOP = 1 to open the audio loop test (parameters are not saved)
  3. AT+QSIDET set side tone gain (parameters are not saved)
    You can follow the above method to test, if it is helpful to you, feedback is welcome, thank you.

Hello Duncan, thanks for your help.

I was missing the modem restart step. Now the loopback is working properly.

Thanks a lot for your support!

Hi Jogagua, thanks for your feedback
I am very happy to be able to help you. If you encounter other problems, please ask questions in Quectel Forums. We will continue to help you, thank you.