Re: [Discuss-gnuradio] USRP FPGA 8-bit Data Ordering

[Paul Creekmore]

Paul Creekmore wrote:
Context: I'm adding new quantization (sample width) options to the 
USRP FPGA configuration.  (Long time in coming; yes, I know.)

Question: I'm seeing that in 8-bit mode, the USRP outputs samples from 
its internal channels in the following sequence (an 8-bit, 8-channel 
example):

    1, 0,     3, 2,     5, 4,     7, 6,    1,0,   3,2,     ...

where each grouping of two channels makes one 16-bit word.

----> What is the rationale behind this convention? 

As I'm deciding how to output 4, 2, and 1-bit samples, it makes much 
more sense to me to use a sequential order, like this (4-bit, 
8-channel example):

    0, 1, 2, 3,   4, 5, 6, 7,    0, 1, 2, 3,   ...

This way if the user writes the data directly to a file, one word 
after another, everything is in sequential order for whatever 
post-processing later.

----> Will the GNU Radio world fall apart if use a sequential channel 
ordering for my output and submit this development for inclusion in a 
future release?


Thanks,
Paul
Amendment:

I see now why the sequence is as it is.  As a real-time program reads 
one word at a time and picks off samples from LSB to MSB, the ordering 
makes sense.  I may just include a setting to reverse the sample order 
for more efficient data recording.  If the powers that be have any other 
thoughts, please let me know.

--Paul
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