Access code detection threshold in benchmark tx/rx scripts

I’m trying to understand the benchmark receive path. The access code
detection threshold is set to -1 in receive_path.py. After looking at
the digital_correlate_access_code_bb block, it appears the INT32
threshold, -1, is being compared with the UINT32 Hamming distance
between the known code and the received code. If I’m not mistaken, C/C++
will do unsigned comparison and therefore any number of errors <
UINT32_MAX (2^32 - 1) will be accepted. Am I reading this incorrectly?

–sean

Inside receive path you have packet_demod block, which is hier block
written i npython. Inside you can find that they assign positive value.

Nemanja

On Fri, Feb 15, 2013 at 3:02 AM, Nowlan, Sean

Inside receive path you have packet_demod block, which is hier block written i
npython. Inside you can
find that they assign positive value.

Ah, just found it.

gnuradio/gr-digital/python/pkt.py lines 140-141 in class demod_pkts:

if threshold == -1:
threshold = 12

Thanks for pointing this out.

Nemanja

–sean

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