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[Discuss-gnuradio] Problem with 8-bit option and dropped samples

From: Lisa Creer
Subject: [Discuss-gnuradio] Problem with 8-bit option and dropped samples
Date: Mon, 20 Aug 2007 23:15:36 -0400

I'm testing the -8 option in various example programs, and haven't been successful in receiving valid data.  The following test resulted in a very brief, flat line being displayed, then absolutely no data showed on the graph, but the program continued to run.

 ./usrp_fft.py -f 100M -d 4 -8
format = 0x288
set_format = True

I decided to try decimating by 4 without specifying the 8-bit option, and I received the 'uO' indicating that samples were dropped from the USRP to host, but data was displayed on the graph, and it was 16MHz wide.  What's going on?

./usrp_fft.py -f 92.7M -d 4

I've also written a data capture script that simply writes data from the USRP to a file, and when I use the usrp.source_s () function (after using make_format, set_format) I get a few initial non-zero bytes, but the rest of the data file is zeroed out.

Any idea what is happening here? I'm wondering if my signal is so weak, that the 8-bit option is truncating all the data off. When running usrp_wfm_rcv.py I can only get one strong FM radio station.

Other questions are:

Is the 'uO' the only indication that samples have been dropped?
Does the number of 'uO's correspond to the number of samples dropped?
What are the buffer sizes?


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