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

[Johnathan Corgan]

On Wed, Jul 9, 2008 at 11:40 AM, Chris Stankevitz <address@hidden> wrote:

> I am troubleshooting a problem with my GPS receiver.  Is it possible to
> collect some 64 MHz data?  I understand the collect will not be long because
> USB2 can't handle the bandwidth, but perhaps buffers on the USRP will allow
> me to make a 1ms collect?

You would have to modify the FPGA code to do so, but it is indeed
possible if not trivial.

The gr-radar-mono code does this (there are of course a lot of
unrelated customizations to the FPGA code as well).  During the
interval in time the USRP is listening for radar echos, is streams
data at 64 Msps into a new FIFO, which accepts 1 sample per clock.
This FIFO is connected to the existing rx_buffer FIFO, which then
streams out the USB at 1 sample per 8 clocks.    This implies it can
only sample at a maximum of 12.5% duty cycle.  (The radar code uses
the gap to send its transmit pulse out and wait for the range gate to
arrive.)

Probably not what you wanted to hear :)

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