Hi everyone, I am using a USRP E312 with GNU Radio 3.7.10.2. GNU Radio has an inbuilt FEC block that supports Turbo Product Codes (TPC). I'm trying to run a flowgraph (completely in simulation) on the E312 that includes a TPC encoder and decoder. The TPC parameters are:
parallelism: 0 row encoding polynomial: 3 column encoding polynomial: 123 K Row: 3 K Column: 18 B: 0 Q: 6 This is a standard 1/2 rate TPC with 6 data byte frame and 12 coded byte frame as per slide 6 on https://kirankarra.files.wordpress.com/2016/01/sep18_02_karra_turbocodes.pdf. On my host machine running Ubuntu 16.04 LTS the flowgraph simulates as expected and my ASYNC FEC encoding and decoding blocks with TPC work and decode properly. I copied across the exact same flowgraph to my E312 and ran it on there, but the decoded bits that come out of the FEC Decoder (diagnosed using a Message Debug block) are all 0s. It's as if the TPC decoder has not attempted to decode at all and prints out the default initialised vector of 0s. I tried all types of TPC decoding including LOG-MAP C factor, LOG-MAP LUT factor, Constant LOG-MAP, max LOG-MAP and Linear LOG-MAP with various levels of iterations from 1-6. All yielded the same response. I even tried to use a ZMQ push/pull sink/source and offloaded the FEC decoding to my host machine while everything else leading up to it was done on the E312 - this works perfectly and the FEC decoding performs as expected on my host laptop. I suspect there's a subtle bit of code that is malfunctioning on the E312, but there's no diagnosis output that hint at where this may be. For reference, I followed the instructions here https://kb.ettus.com/Software_Development_on_the_E3xx_USRP_-_Building_RFNoC_UHD_/_GNU_Radio_/_gr-ettus_from_Source to setup my E312. I have not faced an issue like this before with any other block either in tree or out of tree. Has anyone experienced an issue like this before or know where I should look? Thank you for reading and for your help in advance :). Kind Regards, Ronakraj
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