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TMDX5535EZDSP: Using L/R stereo channels for signal read and feedback for Active Noise Cancelling

dadriano
Prodigy 40 points
Part Number: TMDX5535EZDSP
Other Parts Discussed in Thread: TMS320C5535, , CC3200, BOOST5545ULP, MSP430FR5994

Hi All,

First post from a complete and absolute noob here wanting to build an Active Noise Cancellation Algorithm using a TMS320C5535 DSP. So I was planning to use the TMDX5535EZDSP development board (budget reazons), but then I realised that it might not be suitable for my problem, so I'll want get some of your feedback.

The basic problem is:

1. Input 1: Incoming sound (Microphone 1)

2. Output: Generate an inverted wave of #1 ( Speaker/Actuator )

3. Input 2: Read remaining sound after the actuator, which is used to adaptively adjust the gain of 1 (Microphone 2). 

So the second reading (#3) is totally necessary to make the circuit work/test. However this board only has one Mic-Input. So, my idea is/was that stereo sound is irrelevant for my application, just need one channel, so say that I could use the left-channel for Input-1 and the  right-channel for Input-2.

Question: Does that sound feasible at all? If not, which "budget and Active" development board would you recommend instead for my application?

Thanks!

  • 0
    TI__Guru 65405 points
    Hi Dadriano,

    I've forwarded this to the design experts. Their feedback should be posted here.

    BR
    Tsvetolin Shulev
  • 0 in reply to Cvetolin Shulev-XID
    Prodigy 40 points

    Thanks, I am looking forward to hear the response, my dev board hasn't ship out yet, so I am still on time to cancell it if it doesn't work for this application.

  • 0
    TI__Mastermind 29270 points
    Hi Dadriano,

    I think you will have an easier time using www.ti.com/.../BOOST5545ULP

    This BoosterPack has an on-board mic, can accept a microphone plugged into the line in jack, and can use the mic of a headset plugged into the headphone jack. All 3 mics sources are biased with the MICBIAS from the audio codec. However, the codec can only route 2 microphones to the left and right channels of the output I2S stream (as you have realized). Once inside the C55, the left and right channels are in separate registers and can be treated separately, so no problem. It will be nice to sample these channels synchronously with the CODEC so there is no concern of delay between input and error samples.

    The boosterpack can be run stand-alone or attached to a launchpad like MSP432 Launchpad or CC3200 Launchpad.

    The C5535 eZdsp can also connect two microphones, but you will have to remove R111 and then solder a wire and series resistor to bias the second mic since we only routed MICBIAS to STEREO IN left channel. Alternately, you can use a dynamic mic that does not require any bias, and make the C5535 eZdsp work.

    Several methods are available for ANC. Have you seen this comprehensive app note?
    www.ti.com/.../spra042.pdf

    Hope this helps,
    Mark
  • 0 in reply to Mark Mckeown
    Prodigy 40 points
    Hey, thanks for your recommendation, completely understood. Unfortunately TI sent the packet ~2 hours before your response, so couldn't cancel it on time. I'll try to work out swapping it. Just in case... would be possible to get some schematic of how to modify the C5535 eZdsp ti get the second microphone to work? I hope TI-sales understands my problem and allows me to swap the board. Thanks a lot!!!
  • 0 in reply to dadriano
    TI__Mastermind 29270 points

    Hi Dadriano,

    See below schematic mods to make the right channel have a MICBIAS to connect it to a microphone. You will still need to cut apart a stereo auxiliary cable solder mics to left and right channels, and share the GND wire with the two microphones (GND the body of a can mic).

    I do not think you can return the board after making any modifications like this.

    Hope this helps,
    Mark

  • 0 in reply to Mark Mckeown
    Prodigy 40 points
    Hey Mark,

    Thanks for all the useful information. TI will help me to exchange the device for the BOOST5545ULP. So I have one last question regarding this:

    Would the MSP430 launchpad also be suitable for the BOOST5545ULP, since it has also a DSP? Or rephrasing it: which one would you choose/recommend if cost is not a limitation:

    1. MSP430FR5994 www.ti.com/.../msp-exp430fr5994
    2. MSP432P401R www.ti.com/.../msp-exp432p401r
    3. SimpleLink Wi-Fi CC3200 www.ti.com/.../cc3200-launchxl

    Best,
    Daniel
  • 0 in reply to dadriano
    TI__Mastermind 29270 points

    Hi Daniel,

    To help get you started, the C5545 Boosterpack includes diagnostic software that tests communication with both the MSP432P401R Launchpad and CC3200 Launchpad.

    I have not tried it with the MSP430FR5x FRAM microcontroller, but the Launchpad/ Boosterpack header standard should allow interoperability, and Energia examples for the MCUs are abundant and easy to play around with.

    Here is a great resource for understanding compatibility: http://embeddedcomputing.weebly.com/launchpad-msp430fr5994.html

    Hope this helps,
    Mark