3 Replies Latest reply on May 30, 2017 11:02 AM by userc_38644

    CX3 w/ Audio

      Has anyone successfully set up a CX3 chip to receive audio in addition to video data?


      We're having trouble finding any electrical components that can work with the CX3.


      1) i2s is a no go.  You can output i2s but not receive i2s.
      2) spi is problematic.  It doesn't seem you can output a constant clock with spi.  There is a pause between SSN signal between word reads and even if there is a way to overcome that there is a larger pause when you switch DMA buffers. 


      So in short, how do you get audio along with your video?

        • 1. Re: CX3 w/ Audio

          1) I2S is supported only in Master mode as transmitter 


          2) Have you tested the USBAudioclass firmware in the SDK. What is the delay between the SSN assertion that you see and how much least can you work with? 

          • 2. Re: CX3 w/ Audio

            The delay between SSN assertion is approximately 4-5 clock cycles.  We've been looking for some type of SPI audio bridge that can input the I2S from microphones but we've found nothing so far that doesn't require a constant SPI clock.  

            • 3. Re: CX3 w/ Audio

              Just in case anyone else has this question, tech support responded that there isn't an off the shelf component that does this in such a way that is compatible with the spi lines as controlled by the CX3.  Instead, they recommended using a small Lattice FPGA that takes in the audio data and then can buffer it in such a way as that it can be read by the CX3 over the spi bus.