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Hackfest March 2014 in Karlsruhe[edit]

Post-WSR 2014: 13th to 15th of March 2014 at CEL in Karlsruhe


  • Philip Balister
  • Martin Braun
  • Moritz Fischer
  • Attila Kinali
  • Sebastian Koslowski
  • Jan Krämer
  • Sylvain Munaut
  • Marcus Müller
  • Tom Rondeau
  • Balint Seeber
  • Dimitri Stolnikov


GNU Radio Buffer Architecture[edit]

Primarily Tom Rondeau

  • Buffers need to be more flexibility for accelerators
  • Modifying buffers is potentially hazardous and not trivial
  • first step: get in-place buffers to work
  • if that works, other buffers should be manageable, too
  • for sync blocks without history, that should be doable
  • for concatenated blocks, the most upstream one needs to know the read pointer position of every single downstream buffers
  • missed something in setting up the buffer readers for all upstream blocks

' fixed afterwards for proof-of-concept

  • interweaved backpressure might lead to inefficiencies
  • forking flowgraphs may need special treatment

QT instrumentation[edit]

Tom Rondeau

  • number sink completes the QT toolkit (now equal to WX)
  • nicely configurable, sensible defaults, QT style sheets usable
  • discussion: switch default gen. option to QT (prob. will do)
  • discussion: hide "wrong" gui toolkit for gen. option (problem being that the error message is non-intuitive)
  • Tabs in block properties to reduce complexity


  • Discussion of already available Proposals
  • testing of VNA feasibility (Sylvain Munaut)
  • does work theoretically
  • requires patching UHD, pull req. on github
  • data consistent
  • annoying: B210 does not support timed commands, gives no information on time of tuning
  • not encouraging people to generate last minute proposals


Sebastian Koslowski

  • improved fault handling
  • When block is missing, in the past all connections were undone, the block would just be invisible
  • new: red box, disabled, invalid; gives name of missing block as key
  • all parameter types now string
  • after generation of missing block, everything will fall into place
  • external tool button -> filter design tool
  • external filter tool setting file, but taps just get exported, no external file dependencies of the .grc file
  • tabs
  • new xml element <param><tab></tab></param>, as defined in <param_tab_order>
  • core affinity, buffer sizes, etc always in Advanced tab
  • If no tabs specified, defaults to General tab (means we don't have to change old XML files)
  • Documentation tab for easier viewing of docs

PFB channelizer[edit]

Sylvain Munaut

  • benchmarking
  • trying to improve speed
  • doing a tree of PFBs can sometimes be better than one large PFB
    • channels > 512 can be broken into multiple stages of channelizers
    • cache or other memory constraints may explain why this helps
  • deinterleaving inside the PFB block instead of using a stream_to_streams block didn't work out

QT GUI in external applications[edit]

Sylvian Munaut

  • Support for QTGUI sinks in C++ FGs
  • fixing some swig-related bugs


Balint Seeber

  • based on John Malsbury's work
  • revolves around Simple MAC block
  • OFDM as well as GMSK as Radio interface work
  • TUN/TAP and socket to socket
  • implemented ARP cache equivalent (802.3 Tracker)
  • broadcast for unknown MAC addresses
  • demonstration is awesome
  • test application: send an image progressively
  • ARQ actually working
  • Demo'd by bridging Sylvain over a GR link and routed through Balint's laptop to connect with IRC

GPS receiver in GR[edit]

Attila Kinali

  • self-built GRC flow graph unfeasible large
  • Literature complicated to the uninitiated
  • GNSS-SDR exists
  • highly complex
  • highly modular
  • framework for receiver generation
  • you feed in receiver parameters
  • builds flow graph on runtime
  • great flexibility, but complicated to understand if you're new to this
  • GNSS seems to be using only one core, not realtime
  • Tom needs to revisit GNSS-SDR, refresh friendship with them

' Corgan already working with GNSS and continuing the relationship


  • Discussion on the new FAQ
  • make a meta-FAQ entry point
  • 4 target audiences
  • Students
  • Commercial interested
  • Software Hackers
  • Hams

Some updates to docs and Doxygen[edit]

Martin Braun

  • Better looking
  • Search box available
  • Older versions of Doxygen will generate warnings but still complete