Re: [Discuss-gnuradio] No decimation -- collect at 64MHz

[Johnathan Corgan]

On Wed, Jul 9, 2008 at 11:18 PM, Chris Stankevitz <address@hidden> wrote:

>> The gr-radar-mono code does this (there are of course a lot of
>> unrelated customizations to the FPGA code as well).
>
> I'm going to look at this.  I'll be back with questions...

There are some nuances.  The existing rx_buffer FIFO can only accept
samples at a maximum of 1 sample per 3 clocks. (In the standard build,
it never needs to go even this fast.)  Rather than rewriting the
rx_buffer FIFO, which has a lot of Cypress FX2 battle scars in it, I
created a new FIFO (fifo32_2k.v), then joined it to the existing one.
So the 64 Msps samples go into the new FIFO, and a process streams
these out at 1/3 the clock rate into the existing FIFO.  Finally, the
samples are streamed out to the USB controller at 1/8 the clock rate.
Look in radar_rx.v for this.

There is a state machine in radar_control.v that drives the
rx_control_o wire to enable all this.

-- 
Johnathan Corgan
Corgan Enterprises LLC
http://corganenterprises.com/