Re: [Discuss-gnuradio] Queries regarding FPGA

[Eric Blossom]

On Wed, Mar 01, 2006 at 11:02:12PM -0500, amit malani wrote:
> i am sorry for asking it again, but few of my questions got lost with the
> flow of discussion.
> 
> how control signaling is done?..whats the protocol for it?
> actually when i say these lines.

Please take a look at the code in usrp_standard.{h,cc},
usrp_basic.{h,cc}, and usrp_prims.{h,cc}.  They all go over the USB as
control messages to endpoint 0.  The control messages are parsed in
the FX2 and acted upon.  Generally speaking they end up issuing
transactions on the I2C bus or SPI bus.

The FPGA registers, AD9862 regs and daughterboards appear on the SPI bus.
The configuration eeproms and daughterboards appear on the I2C bus.

See the USRP schematics for details.

usrp/firmware/include/usrp_spi_defs.h contains the defs for the SPI bus.
usrp/firmware/include/usrp_i2c_addr.h contains the standard i2c
addresses.  Some daughterboards use others that are a function of
which slot the d'board is plugged into.

>         src = usrp.source_c (0, decim)
>         src.set_rx_freq (0, IF_freq)
>         src.set_pga(0,20)

> how actually it gets translated and conveyed to the master_control(?) module
> on FPGA to do the needful. am I not he right path?
> 
> please let me know,
> thanks in advance
> 
> amit

Eric