Re: [Discuss-gnuradio] Fewer than 8 bits per sample FPGA support

[Eric Blossom]

On Tue, Mar 13, 2007 at 01:10:53PM +0100, Davide Anastasia wrote:
> Il giorno dom, 04/03/2007 alle 22.55 -0800, Peter Monta ha scritto:
> > > The "short" version doesn't touch the data.  You'll be able to
> > unpack
> > > it youself.
> > 
> > Strange, I had some problem with rx_cfile not seeming to respect
> > the width parameter.  I'll try it again. 
> 
> Hi List,
> I'm sorry to reuse this old topic, but I'm working on this feature.
> 
> I recompile FPGA firmware using Peter' mod to obtain 1, 2, 4 and 8 bit
> width sampling. I'm using this firmware and the script attached to try
> it, but seems it doesn't work. I don't know if Peter (or someone else)
> use correctly this mod.
> 
> I receive that:
> 
> address@hidden:/home/rocker/Tesi/My Works/GNU Radio
> Experiment/rx_cfile# ./usrp_rx_cfile.py -m -f 1.575G -w 4 -R A -d 16 -N
> 1000 output.samples.4
> Upload new firmware!
> Using 4 bit sampling
> format = 0x248
> set_format = False
> Using RX d'board A: DBS Rx
> USB sample rate 4M
> 
> Format setting fail.

I suspect you're getting caught by the sanity check in the host
library code.

Take a look at usrp_standard.cc, usrp_standard_rx::set_format and
remove the test for rx_format_is_valid.

I think the right way to work around this is to add another field to
the FPGA capability register that indicates whether or not the shifter
is implemented.

Eric