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Dual role USB+I2S on CC85x1

d0m
Prodigy 65 points

I know this is not possible with the current version of PurePath Wireless Configurator, but I'm sure it could be accomplished in software. What I'd like to see is Autonomous mic base station prior to USB enumeration and USB mic soundcard afterwards.

Looking at a pair of images generated for these roles, there appears to be substantial overlap. I can't see it being too difficult to enable I2S output prior to enumeration. Autonomous base station seems rather trivial and a subset of USB mic soundcard as the PLL can be kept fixed rather than having to adapt to USB SOF rate. In fact I don't see the need to synchronize to SOF even in USB mode in case of mic application - the easiest solution would be asynchronous IN endpoint and fixed audio PLL settings.

A crude workaround for this scenario would be to re-flash the CC85x1 every time the device role changes, but apart from it being decidedly non-elegant, it seems one would quickly run into the stated maximum 1000 flash erase cycle limit.

Could some good soul at Ti/CC customize the firmware for us?

  • 0
    TI__Mastermind 21125 points

    Hi d0m, 

    There are limitations in HW preventing this from being possible I'm afraid and am not aware that this limitation will go away anytime soon. 

    Regards, 
    Kjetil

  • 0 in reply to Kjetil
    Prodigy 65 points

    Hi Kjetil,

    As I understand it, the chip runs an arbitrary code from flash. I could understand why simultaneous I2S and USB is not possible, but why should it be impossible to do either/or? Is the internal flash size the limit? Could there not be a powerup option - via GIO or EHIF or nonvolatile store - to start either autonomous I2S or autonomous USB? No need to switch between the two on-the-fly, just a way to select one of the modes after reset.

    The USB code is capable of running the wireless streaming and synchronizing the wireless network clock to USB SOF. How much difficulty can there be in keeping the clock fixed and sending data to the I2S peripheral instead of the ISO endpoint buffer? Need not be elegant, need not be full featured basestation, 48kHz only etc. same as for USB soundcard mode.

    Thanks for chiming in on this!

  • 0 in reply to d0m
    TI__Mastermind 21125 points

    Hi d0m,

    I can't go beyond just stating that there are limitations preventing this from being possible and there is no short term fix around this. 

    Understand that this pose some real limitations to our system (you are not alone in wanting a feature like this), but if you can sink the board space and cost associated with two CC85xx devices on the master side you could let the VBUS line from USB drive the reset pin on the 2nd device to GND. If this can be a possibility, add me as friend here and we can talk more openly about this opportunity and how this can be achieved. 

    Regards, 
    Kjetil