First flight with the Raspberry Pi 3

We managed to get our hands into a Raspberry Pi 3 and decided to give APM a try with it using the PXFmini. Here’s a walkthrough over some of the tests that our team conducted: 

Benchmarking

So, down to the benchmarks, we performed 3 types of tests using sysbench and the default Raspbian images (no APM running for now). SysBench is a modular, cross-platform and multi-threaded benchmark tool for evaluating OS parameters that are important for a system running a database under intensive load. The output of sysbench looks like this:

sysbench --test=cpu --cpu-max-prime=20000 run

sysbench 0.4.12:  multi-threaded system evaluation benchmark

Running the test with following options:

Number of threads: 1

Doing CPU performance benchmark

Threads started!

Done.

Maximum prime number checked in CPU test: 20000

Test execution summary:

   total time:                          477.3324s

   total number of events:              10000

   total time taken by event execution: 477.3236

   per-request statistics:

        min:                                 47.69ms

        avg:                                 47.73ms

        max:                                 85.54ms

        approx.  95 percentile:              47.72ms

Threads fairness:

   events (avg/stddev):           10000.0000/0.00

   execution time (avg/stddev):   477.3236/0.00

 

The output is graphed against the Raspberry Raspberry Pi 2 (note that smaller bars indicates better results):

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sysbench --test=cpu --num-threads=1 run



HinsJCn2SeFkgFTYC-TDFUR0pVB6Dv1ddZy0dzMpWRq0HLSFqsjmuyCHKODO6IM3_5rSdCzT0j9ThNMsQQ-0uWX2K_Nrl2OVVC10I1Jl8cfzrMYjHSS6WhHSHfcyfxrDweaFmahL

sysbench --test=memory run --memory-total-size=2G

rURY_MBXrYtN-rqabZnH8VUv6iduqjH7r6XHCi4EnCh5nLgu5L-uZm5Y9FnuCXvB_Jgn5hau0pECBAupVCMUYI6NL6VN4ZJuZE8M0YKHybFqtEfKtxbb1rBafPPZjVwcqxh2tSpC

sysbench --test=memory run --memory-total-size=2G --num-threads=1 --memory-oper=read

The 64 bits CPU of the Pi 3 dramatically improves the results of this particular tests over the Pi 2. It’s 40% - 60% faster.

Mounting the autopilot:

We mounted the shield as follows which proved to be robust enough. Vibrations were kept at a reasonable level as will be shown later in the log analysis:

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Flying with APM and log analysis

After a short flight we started some checks. The official documentation of APM will tell us:

“Check the scale on the left and ensure that your vibration levels for the AccX and AccY are between -3 and +3.  For AccZ the acceptable range is -15 to -5.“

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Fine on this. We also felt that the drone was reacting really good so made a few plots that convinced us about the autopilot responses with the Raspberry Pi 3:

dyBj024hPwbAOYdrU9EFfT45nomahOT_rh3JOoEtow-x5foj-DHiYmRX7e5fMX-nobv2G8Dgea64VkjCkwp62HqPtaHSpBRZfCBNPrPbjxAZJSxgVGof3XulLSuhTf-1SJkbTQ1N

 kpzZsCpTKZ3GHyCAZq623y_9CN9wbYO2m6f3d91B6j1It7N0h1NVUMTo_-CTydPPzswm6wj0nq9mkm8ZuZIxcYyI7uaiJJUJeFNWEix371Ef88chwdqomkPI1bt4N0jJPGCFZkTb

Conclusion

Raspberry Pi 3 is a great candidate to make APM Linux autopilots using the PXFmini!. Having Bluetooth and WiFi is indeed a great asset removing the need of using additional USB dongles unfortunately, WiFi is solely b/g/n and does not support the 5 GHz frequency band (which comes handy when flying with RC controllers that work in the 2.4 GHz band).

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Comments

  • The OS is available for download on our docs. In case you want to try it.

  • @JB, I agree that the new Raspberry compute module if it will feature the new SoC of the Pi3 should make an excellent cheap CC. 

    I have the old version and I am very happy with it, it has a very small footprint

  • Lol Jerry. Do you mean this one that RS carries still (and element 14 etc):

    http://au.rs-online.com/web/p/processor-microcontroller-development...

    ---

    @Victor

    There's a new compute module coming with the 64Bit Pi3 hardware.

    Jurgen from Auvidea is already making boards with PXH2, Edison and TX1.

    If another version of the PXF is made I'd really like to see a MCU instead of the PCA. Plus it will be necessary to route out both some USB and the MSI for camera etc use. With the SO-DIMM slot connections of the compute module I'd try to keep it as compact as possible for small frames. It should also follow the same schematic as the existing module, so it's possible to get a head start now already before it comes out. It could be marketed as the "improved version" of the Zero PXFmini, with computer vision, for only some $35 more. (the cost of the Pi3 Module over Zero).

    Layout wise I'd have the 2x USB/MSI up one end for camera/ext. wifi with PWM/RC up the other end for ESC etc. It's also possible to integrate a 4ch ESC in the same form factor as a extra daughterboard underneath the PXF for super compact setups with 3 stacked PCBs (under 50g).  

    Regards

  • Hi Jerry,

    The TX1 is indeed interesting. I'll PM you on this matter.

    Regards,

  • Pi computing Module has been obsolete now, RS-online now dropped it.

  • Great report for the timing and quality.

    I will begin tests on nVidia TX1, hope we can work together.

  • JB,

    I have no experience with the pi compute modules but sounds like an interesting idea. Will give it a though.

    Kabir,

    No it does not unless you apply a lot of force. The header and the spacers seem to do a pretty good job.

  • Developer
    Nice!
    Does the single-sided mounting make plugging in connectors difficult? Does the board not flex or bend?
  • I like forward to the new A53 Pi compute model based PXF mini....when will you make it? The new compute module will be here in a few months. ;-)

  • None that i've been able to identify. For now, we are powering the Pi3 through the autopilot shield and using several dongles on it. Raspberry pi org mentions that it may be more power hungry though:

    This time round, we’re recommending a 2.5A adapter if you want to connect power-hungry USB devices to the Raspberry Pi.

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