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TLV320AIC3100EVM-U: Microphone input not working

Part Number: TLV320AIC3100EVM-U

Hello,

when i plugged this evm the first time into my pc, then the drivers seems to be correctly installed. After that, i can choose this evm for playback/recording. When i start the "CodecControl" programm, then the evm becomes initialized and the playback is working, also it seems that as default the DIN=>DOUT loopback is active, because i can record to music i feed into the codec. So far so good.

I adjusted and verified the registers with the "Register Inspector" so that the microphone input should be deliverd to DOUT, but this isnt working! The most strange thing is, that the drivers/amplifiers/terminals for playback/recording paths are active after the basic initialization, because i can hear audio on the headphones (also checked page 1). But when i check the page 0, then the ADC/DAC flags are all 0 which is obviously wrong...

What are the steps that must be done, so that instead the loopback the mic input can be recorded?

Thanks and kind regards,

Lukasz

  • Lukasz,

    When Codec Control starts up, it runs an initialization script on the EVM. This can be viewed by going to View/Init Script
    This init script IS setup for recording, there are no register writes made to enable the loopback mode in that script.

    If you press "refresh" in the register inspector, it should reflect the Init script.
    Can you tell me more about the microphone you've chosen to plug in?

    best regards,
    -Steve wilson
  • Hello Steve,

    the microphone is attached to headphones and its from Sennheiser. I cant tell you the exact model because its not written on this headset, but its a cheap one.

    What i can say is that we are using the AIC3100 Codec already on our mainboard and the mic is working there. The reason i look into this evm is, because the input on the mainboard is a little noisy and i want to see how it behaves on the evm, if something can be improved and/or we have to use the DSP blocks.

    The script stuff seems to be very strange, so i can use the AIC3111 scripts for the AIC3100?

    When you say, that the default initialization is for recording, then why are the ADC flags all 0? Why is the Playback working without using any additional scripts, when i occupy the headphone jack, but the DAC flags are also 0?

    Can you tell me what is the exact purpose of the VCOM Terminal?

    Also, i found the reason for my problems: The headphone/microphone jack cant not be used/occupied at the same time .... why?

    Thanks and kind regards,

    Lukas

  • Lukas,

    I admit i hadn't used the register inspector in Codec control. I am going to be blunt and say that the register inspector is a bit clumsy. It doesn't seem to read the ADC or DAC flags. If you open the command window, you can perform a read command on those same registers,
    for example when I run the command r 30 24 01, It returns "C0" and when I run the command r 30 25 01 it reads "BB" which is exactly what I would expect given the init script.
    I would recommend not bothering with the Register inspector as it is clearly buggy.

    Being from the same family the AIC3111 and AIOC3100 have nearly identical register maps. The AIC3100 doesn't have stereo Class D amplifiers like the AIC3111, it has a more powerful mono Class D, but there is no problem running the AIC3111 init script on the AIC3100.

    There is no reason why the headphone and microphone jacks cannot be used at the same time. The MICDET pin is connected to the Headphone jack, but the micDET function is disabled by default, and it wouldn't automatically shut off the mic circuit or anything. can you explain your setup?

    VCOM is connected to the negative input of the PGA with Single ended inputs are used on the positive terminal. this provides a common mode voltage to the negative terminal so that there is no DC offset on the output. All inputs have a common mode offset. If using a differential input, VCom isn't necessary because Mic1LM provides the same common mode offset as MIC1LP. does that make sense?

    best regards,
    -Steve wilson
  • Hi Steve,

    thanks alot for the answers.

    Ok @ Register inspector as it is clearly buggy and AIC3111 and AIOC3100 have nearly identical register maps.

    There isnt much setup going on. I plug the evm into USB, start the CodecControl programm and as last plug in the headphones and/or mic, thats it. Of course i choose in Windows those devices for recording/playback. I also noticed that the switches on the evm behaving strange, i cant get to the blinking led as described in the user manual for switching applications, theres also nowhere any descriptions what those applications are?

    Alright, so VCOM stands for common mode voltage, and sure with differential signals the subtraction will remove the offset. So i guess that VCOM is the CM-Register.

    When should or how should i use it? Because per default, VCOM/CM-Register path is selected in the ControlCodec programm, but when i dont use this path, the recording sounds much better, is that normal?

    Thanks and kind regards,

    Lukas

  • Lukas,

    yes, The applications switching isn't well documented either. The EVMS will not come with any applications pre-programmed. You will need to program this by clicking File->EVM Applications. Then right click that window and choose add application, then Add Script.

    once you've done this, you will need to "update EVM"

    regarding the VCOM, I see what You are saying, it seems that I get a DC offset when I connect the VCOM. Let me reach out to the design team to see what is going on here and I'll get back to you by monday 8/28. (the design team head is traveling so it may be a few days before he can respond) For now no not enable the VCOM input.

    best regards,
    -Steve Wilson