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Pure Data on Raspberry Pi 2 with real-time kernel and Cirrus card?

dmlandrum

I'm aiming to create a Korg Wavedrum-like project. The idea is to have a tensioned drum head miked with two piezo contact mics (one at center and one at edge) feeding into the Cirrus card so the signals can be processed by PD into something more interesting. I'm not talking about just using the piezos as triggers: the audio they capture can be part of the final sound.

 

I know people have said the RPi is not a good platform for DSP, but I think for this application it will be good enough. The problem I'm having right now is with how to set up a real-time kernel on the RPi 2, which is what I'd like to use as it has more RAM and processor power. I've tried Google and the search here, but didn't find anything I understood. Is this possible, and does anyone know where some good information can be found on it? It's been a long time since I've used Linux, so I'm really rusty at the moment.

 

Thank you very much for your help.

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  • 0

    I'm not so sure the Cirrus card will work for me now. It looks like they combined the mic input and audio output together into one connector. I need both available at once. I've tried looking up documentation for what the header pins are connected to, but I can't find anything (the link to the schematic is a 404). Can anyone help me with this? Thank you!

     

    Honestly, it looks like they're not using anything close to the full potential of the chip, unless those header pins let me get at it.

Reply
  • 0

    I'm not so sure the Cirrus card will work for me now. It looks like they combined the mic input and audio output together into one connector. I need both available at once. I've tried looking up documentation for what the header pins are connected to, but I can't find anything (the link to the schematic is a 404). Can anyone help me with this? Thank you!

     

    Honestly, it looks like they're not using anything close to the full potential of the chip, unless those header pins let me get at it.

Children
  • 0 in reply to dmlandrum

    Hello Darren,

     

    I have collected a really wide documentation on Cirrus while working on the audio part of the Meditech project. The problem is that I can't attach nothing to a comment post. Let me how can I send you some images and pdf.

     

    BTW, it seems I am a bit obsessed on the mutability of the Internet but when I find good documentation on some site, especially personal blogs or small forums, I print the pdf of the content just to avoid in future those damn error 404 from disappeared sites image Let me check if I can do attaching some images.

     

    Enrico

  • 0 in reply to dmlandrum

    Well, maybe I have got it image The following image is where the jack are positioned on the board and their meaning:

    image

    So fron left to right, from the Cirrus Logic Audio Card schematics you can see:

    image

    A normal mono microphone line-in jack

    image

    A normal stereo line-out jack

    image

    This is the jack that interest you. The order of the pins (as shown in the schematic) is the same of the earphone + microphone smartphone plugs.

     

    Take in account that the use of one input and output channel respect another (line in, headset, line out, speakers etc.) should be configured in the system with one of the available bash scripts.

     

    Enrico

  • 0 in reply to balearicdynamics

    Okay, so I might have to use the line-in with a pair of external mic preamps, which isn't that big of a deal (I'll need a very high-impedance input for piezo contact mics anyway), as I'll still need a bipolar power supply (+/-12V should do) for balanced line drivers.

     

    I was really hoping there was a way to separately access all the functions of the chip, but this will do. Thank you for the help!

  • 0 in reply to dmlandrum

    Hi Darren,

     

    I suggest you explore the content of the scripts that automatically set the different input and output lines of the board. It is part of the pre-installed RT Kernel and is explained in the manual. As you edit the sources you will see a good documented set of commands that probably are what you are searching for. These batches are just scripts that automate the presets but with a simple analysis you can do your own as needed. Let me know if you need help about this.

     

    Enrico