[hpsdr] [OT] Shipping container overload

[Eric Blossom]

On Wed, Mar 15, 2006 at 12:03:04PM -0800, Christopher T. Day wrote:
> It's all still musings in my head at this stage, but I wouldn't think
> the CPU core of the FX2 had to do anything in a great hurry; all the
> heavy USB transfer lifting would still be done by the USB core. The CPU
> would only have to handle configuration changes and COMMAND messages.
> This would make a USB device that could - maybe anyway, I have to read
> the MS DDK documentation - yield a device that worked with generic USB
> Audio Device drivers.

Makes sense.  
I suggest checking the USB specs for the audio device class.  It's a standard.

> And speaking of commands, since the FX2 has a direct I2C master on chip,
> it could be used to send configuration commands to the ADC/DACs and save
> some space in the FPGA.

You could do that.  

That's what we did on the USRP, but in retrospect, I think it was a
mistake.  The problem is that if you hang it all off the FX2 I2C, then
the FPGA *can't* control the stuff.  It all depends on what you think
you might want to do.  If it's possible that you might want to run a
control loop in the FPGA that needs access to the I2C bus, then hang
it off the FPGA.  [Actually on the USRP, we controlled the ADC/DACs
over the SPI bus, which we bit-banged from the FX2.  Same conclusion,
however.]

Eric

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