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Interfacing external electret MIC to AIC3100 EVM

LJay
Prodigy 90 points

Hello,

I am evaluating AIC3100 EVM. I was able to verify Line IN, Line OUT and Speaker interfaces. But I am not able to get the board working with an external electret microphone. I tried using MIC LP and MIC RP pins and both cases didn't work. Here is what I tried:

Case 1:

1. Soldered MIC across J2, Pin 2, MIC LP and J2, Pin 1-GND.

2. Jumpered W3.

3. Jumpered W1, Pins 2-3

 

Case 2:

1. Soldered MIC across J2, Pin 3, MIC RP and J2, Pin 1-GND.

2. Jumpered W2.

3. Jumpered W1, Pins 2-3

Please let me know, how I can test the board with external MIC.

 

Thanks,

Lakshmi

 

  • 0
    TI__Mastermind 46195 points

    Hello Lakshmi,

    Please try the attached script with Case 1. Jumper W1 can remain as 1-2, since MICDET is suitable for headset-type environments.

    Also, it would be good to measure the mic output with a scope while playing a sinetone in front of the mic to verify that the mic is working properly.

    Regards,

    J-

  • 0 in reply to J-
    Prodigy 90 points

    Hi,

    I tried the script you provided. I played a ringtone from my phone near the MIC at full volume. It showed a sine wave, but the amplitude (pk-pk) was only 300mV. The AGC gain (0 to 59.5dB) does not seem to have any effect.

     

    I also, tried playing music through the LINE IN connector (no MIC). With even very low volume on the input, the output on the headphone was very good when I used max gain settings. But I saw good signal only on the MIC RP pin (2V + signal swing). The MIC LP pin did not have Bias voltage. I noticed when I used an external MIC and also plugged in a headphone, it removed the MIC Bias voltage. When I checked the datasheet for the register settings, it looks like by default the MIC Bias must be present regardless.

    The MIC I am using has a sensitivity of -42dB and a Sound Pressure Level of 110dB. So it should work fine. Please comment.

    Thanks,

    Lakshmi

  • 0 in reply to LJay
    Prodigy 90 points

    Hi,

    The script you sent actually disables all the MIC connections.

    Except audio through LINE IN (fed from another device), audio from an external electret microphone or a PC type microphone does not work. Even with LINE IN, even though it works, I am not able to measure a good signal on the MICLP or MICRP inputs. The gain settings (0 to 59.5dB) and DVol settings seem to have no impact.

    Please reply ASAP.


    Thanks,

    Lakshmi

  • 0 in reply to LJay
    TI__Mastermind 46195 points

    Hello Lakshimi,

    Could you try executing the script using the command-line interface of this software: http://www.ti.com/litv/zip/slac349a ?

    Regards,

    J-

     

  • 0 in reply to J-
    Prodigy 90 points

    That did not work either. Its a very simple interface right ? Does it need a pre-amp ?