Re: [Discuss-gnuradio] setting registers

[Brian Padalino]

On 7/16/07, George Nychis <address@hidden> wrote:
> So I think what Leo is getting at is how to actually perform the read or
> the write to a register for the C/S packets.  For instance we have the
> read/write register commands where the application says read from
> register X or write this data to it.
>
> This would pertain to OP_WRITE_REG, OP_WRITE_REG_MASKED, OP_READ_REG,
> and OP_READ_REG_REPLY:
> http://gnuradio.org/trac/browser/gnuradio/trunk/usrp/doc/inband-signaling-usb
>
> I'm assuming what Leo is wondering, is when I pass him register 3 for
> instance, how he can actually perform the read or write.

Major surgery.  Disconnect the I2C pins between the FX2 and the FPGA
logic (float the pins coming in, and ground the pin going out?).  Then
every register has to be put into a register file which the C/S state
machine has the ability to read/write, and create input ports for each
of the modules which have registers associated with them.

You may be able to use a spare pin connected to the FX2 to perform
some weird loopback thing where the host sends to FX2 which then sends
to the FPGA.  The FPGA notices it must write a register, so it sends a
special packet back to the FX2 which the FX2 parses after it reads (no
DMA here) and then performs the I2C write, but that is a big old mess
too.

Both are pretty involved modifications - at least that's my take on
the whole affair, which I could be completely wrong about.

Brian