Friday, September 19, 2008

The Communication System

As we promised, here is the detailed status of our multi-hop communication system:
  • The low-level control FPGA boards are ready. They implement the PIDs ensuring smooth operation of drivers and sensor readings from the encoders. We devised a flexible protocol to send commands to the motors and get timely sensor readings to and from both the on-board computer and the mid-level control (pattern-generator) board. We used Altera DE2-70 boards, communication takes place over Ethernet.
  • With a well-defined protocol we can now begin porting the Matlab pattern-generator code to the FPGA board which will ensure real-time performance.
  • We are coding the software which will run on the on-board computer. Our current focus is getting good performance out of the stereocamera and delivering a reasonably good (and packet-loss ready) video stream. We are still having some difficulties with buggy libraries and fuzzy-behaving encoding software, had to write to PTgray a couple of times. We have our Linux system running on the Fanless VIA EPIA, we tested all basic interactions with the various components.
  • Good news from the Multi-hop communication system: our Fonera nodes are up and running with B.A.T.M.A.N., a robust multi-hop communication system. Testing shows very good range (with some hops we can communicate from side to side of our large and thick-walled historical building with only 10% packet loss) and a comfortable bandwidth of more than 500 kB/s. The home-made battery pack got us 2.5 hours of run-time in little weight.
As we reported in our previous post, we are still waiting for some equipment. As more and more subsystems get ready, our tests are becoming increasingly realistic. In a short time we'll run a complete motor tele-operation test.

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