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Analog and Digital Volume Control with 8531 and 3204

Arthur Matteson
Prodigy 25 points
Other Parts Discussed in Thread: CC2591, CC8531, TLV320AIC3204

Hello,

We have successfully used the CC8531, CC2591, and TLV320AIC3204 to implement a wireless microphone system for guitars.  Our master (marketed as a transmitter) mounts inside a guitar and currently takes two analog inputs from two different types of microphones, on the left and right channels.  An analog volume control is converted to up/down button pulses with an 8-bit microcontroller and the 8531 changes the volume inside the 3204 accordingly by means of the analog PGAs.  These two channels are then sent over the air to a slave (marketed as a receiver) where they are balanced and mixed, including a volume control.  All of this works great now.

Due to low availability of our analog electret microphone, we would like to replace it with a digital microphone.  We also hope to reduce audible noise by doing this.  Our concern is that the volume control via the 8531 will not work due to one of the 3204 PGAs now being out of the loop when using a digital source.  Our questions are the following:

1. Do registers P0/0x53 and P0/0x54 affect the volume of a digital microphone on the 3204?

2. If not, what options are available to change the volume of a digital microphone locally?  What about filter gains?

3. Is it possible for the 8531 to write to two different registers in the 3204 to change volume, i.e. the PGA on the right channel and the digital control on the left channel?  Is this accessed through "aic3204.ppwadd"?

Thank you for any help that you can provide.

Arthur Matteson

  • 0
    TI__Expert 7160 points

    Hi Arthur,

    I am sorry for the delayed answer. 

    I believe your two first questions are better suited in this forum: http://e2e.ti.com/support/data_converters/audio_converters/default.aspx

    Can you please post these two questions here instead?

    For question 3:

    You are right. Inside the aic3204.ppwadd you will see the following at the bottom of the file:

    <vol_ctrl_spec dir="Input" type="Volume" io_channel_mask="01">
        <pre_patch_cfg_sequence>
            w 30 00 01 # Select register page 1
        </pre_patch_cfg_sequence>
        <vol_precision>1</vol_precision>
        <vol_negate>0</vol_negate>
        <vol_add_value>0</vol_add_value>
        <vol_left_shift>24</vol_left_shift>
        <vol_field_size>8</vol_field_size>
        <patch_i2c_addr>30</patch_i2c_addr>
        <patch_reg_addr_size>1</patch_reg_addr_size>
        <patch_reg_addr>3B</patch_reg_addr>
        <patch_reg_data_size>1</patch_reg_data_size>
        <patch_reg_data>00</patch_reg_data>
        <patch_read_mask>00</patch_read_mask>
    </vol_ctrl_spec>

    The first line here is important. It specifies whether this is for input volume or output volume. It also specifies that this is for type: Volume (you have similar sections for mute and unmute). And it specifies the logical channel "01". So this section specifies what happens with the left audio channel input volume when the input volume changes. As you can see the CC85xx will write to the register address 3B in the aic3204. And the pre-patch sequence makes sure that we use page 1. Page 1 register 3B is the Left MICPGA volume control (see the TLV320AIC3204 Application Reference Guide: http://www.ti.com/lit/ml/slaa557/slaa557.pdf). You have a similar section for logical section "02" and you will see here that the register is 3C which corresponds to Right MICPGA volume control.

    You are free to change this as you like. I recommend to take a copy of the aic3204.ppwadd and paste it in:

    C:\Users\<user>\Documents\Texas Instruments\PurePath Wireless Configurator\audio_devices\

    Then you do your modifications to this file. In the PPW configurator this new file will have precedence over the one in the PPW Configurator install folder and you will see that you are using the file in My Documents because you should now see a # before the audio device name in the drop down list in the PPW Configurator.

    Hope this answered your question.

    Best regards

    Kristoffer

  • 0 in reply to Kristoffer S
    Prodigy 25 points

    Kristoffer,

    Thank you for your detailed answer.  It sounds like I should be able to get this to work properly.  I will post my other questions in the appropriate forum.

    The only other curiosity for me was what "vol_precision" and "vol_left_shift" do.  I would have expected the shift value to be zero without exact knowledge of what it does.  Also, is it possible to write to multiple registers at once by duplicating a certain part of the sequence?

    Regards,

    Arthur

  • 0 in reply to Arthur Matteson
    TI__Expert 7160 points

    Hi Arthur,

    Have a look at the chapter Audio Device Definition Files in the built-in help system in the PPW Configurator. Also to see how this is done in practice you can study the examples allready there (for example tha aic3101.ppwadd or the aic3204.ppwadd) and at the same time look at the corresponding data sheet with register description for these devices.

    Unfortunatelt it's possible to control only one register per audio channel for volume control.

    Best regards

    Kristoffer