Re: [Discuss-gnuradio] Queries regarding FPGA

[Eric Blossom]

On Mon, Feb 27, 2006 at 10:41:10AM -0500, Clark Pope wrote:
> 
> FYI, It's not clear that going to a driver is going to make too much
> difference.  It might, but I'd start with the user mode code.
> Measure twice, cut once ;)
> 
> There is some fairly straight-forward work that can be done to reduce
> the latency of the user mode code, and that's probably a good first
> step.  This would also including enabling real-time scheduling for the
> signal processing threads (SCHED_FIFO), reducing the amount of user
> space buffering for the USRP (no need to mess with the generic
> buffering in GNU Radio, it's not the problem), and transfering smaller
> chunks of data across the user/kernel boundary (that that won't help
> throughput!).
> 
> Eric
> 
> Yes, I will probably monkey around from within user space originally, but I 
> should have mentioned that my end goal is to have the USRP appear as an 
> 802.11 network node to the OS so that it integrates with ethereal and other 
> network tools just like any wi-fi card would. So I'm stuck with developing 
> a custom device driver (probably adapted from wlan-ng)  anyway.
> 
> -Clark

You can do that from user space.  Not sure about the wifi specific
extensions, but there's already code in user space that has GNU Radio
show up as an "ethernet" interface (gr0 under GNU/Linux).  We use the
tun interface.  See gnuradio-examples/python/gmsk2/tunnel_ip_null_mac.py
and the README in the same directory.  It talks about how to ifconfig
the gr0 interfaces, add routes, etc.  See also
/usr/src/linux/Documentation/networking/tuntap.txt

Eric