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Thread: Numa V2 - Quad Mech

  1. #21

    Re: Numa V2 - Quad Mech

    Well, that capacitor will work great as a pull-down for a short while :-)

    I recommend the Saleae kit. Even their cheapest one is better than running blind. Rolling your own is fun and all, but the Saleae software is very nice. Not super feature-ful, but highly polished.

  2. #22
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    Re: Numa V2 - Quad Mech

    Quote Originally Posted by Brooks View Post
    Connectors are how Murphy emerges from his evil lair. Consider cutting the connector off the servo wire and soldering all three wires to the board...
    The wires going to the board are all non-moving. The runtime of the robot is measured in tens of hours at most, and so I won't be worrying about these wires. The ones between the servos on the leg on the other hand will at least be fully replaced with new ones.

  3. #23
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    Re: Numa V2 - Quad Mech

    Still working on this! Slowly. Satisfying things I've accomplished sporadically:

    - Desoldered the ARM chip off my Hydrabus and procured replacement (from china, hopefully not fake); haven't soldered new on on yet.
    - Got fancy hot air reflow tip for hitting the pins of the chip exactly.
    - Generally finished porting all the logic... Now I need an actual robot.
    - Got plotting script working so I can plot the positions that my IK is generating for servos (a few things need fixing)
    - Used the mnfy python3 module to make a script to minify the modules that I upload to the HydraBus board. I think I was over the storage size available thanks in part to copious comments.

  4. #24

    Re: Numa V2 - Quad Mech

    Celebrating progress is what it's all about -- nothing's ever "finished" anyway :-)

    thanks in part to copious comments
    Can you upload compiled pyc/pyo files? If so, python -O will strip the comments.

  5. #25
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    Re: Numa V2 - Quad Mech

    That is a good point, heh. Not 100% sure I'll use the minification always, either, as you can live-debug with the python interpreter running on the board. I may need that for debugging frequently :|

  6. #26
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    Re: Numa V2 - Quad Mech

    Switched to a pyboard instead of the hydrabus. It's only disadvantage is fewer mounting holes. And maybe that I like blue more than green :P

    Correspondingly made a perf-board shield for the pyboard with 5V regulator, pololu power switch, dynamixel connectors, and a few headers for laser and for camera power. Nothing too fancy.

    In addition to a earlier plotting script that I got working, I got a test script to do a bunch of time-step calculations for the walking. It looks like the IK currently uses about 18% of CPU cycles running at 50 Hz. So I won't be doing any speed-based optimization...

    Ironed out a few bugs along the way there, too. I think these mostly related to not realizing that array objects in micropython don't implement __mul__(), and then realizing I'm just doing 2D vector products and working with lists is good enough.

    Next, up, get the full code running and making sure the shoulder servos move as expected!

  7. #27
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    Re: Numa V2 - Quad Mech

    More slow progress, mostly yesterday. Got the pyboard properly communicating with the motor drivers. It was a series of mistakes that I had to find along the way to getting that working. It seems the micropython docs are inconsistent, with some old and new ways of doing things (like PWM) and only minimal examples (so I didn't realize I also needed to enable the associated timer, for example).

    I also managed to drain my LiPo battery at some point, at least I have spares sitting around.

    It seems the dynamixel wizard no longer works properly on my Windows desktop, even after a reinstall. But it does see the 4 shoulder servos, so I don't think I fried any of them.
    Click image for larger version. 

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    The servos seem to move a bit, but not like I'd expect; Probably issue with my positions being generated.

    Next step is getting the servos moving cleanly. Then probably cleaning up the values that I generate from my gaits. I may seek out a cheap set of phantomX leg plastic, rather than designing my own set of legs right away.
    Last edited by Gertlex; 10-16-2017 at 01:22 AM.

  8. #28

    Re: Numa V2 - Quad Mech

    How does the PyBoard compare to, say, a Raspberry Pi Zero W?
    The Pi has a much beefier CPU, and more RAM, and stuff. And is still cheap.
    And you can run as much Python on it as you want :-)
    The PyBoard has some peripherals that the Pi doesn't, but at $45, you could just add a Teensy LC or something to that Pi and still come out ahead :-)
    (Except on size)

  9. #29
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    Re: Numa V2 - Quad Mech

    Quote Originally Posted by jwatte View Post
    How does the PyBoard compare to, say, a Raspberry Pi Zero W?
    The Pi has a much beefier CPU, and more RAM, and stuff. And is still cheap.
    And you can run as much Python on it as you want :-)
    The PyBoard has some peripherals that the Pi doesn't, but at $45, you could just add a Teensy LC or something to that Pi and still come out ahead :-)
    (Except on size)
    While I've played with a RPiA, I've never used the zero. I certainly wouldn't want to be running raspbian, and I don't have any desire to experiment with more minimal OSes... so the pyboard is ultimately a win in the "up and running" category for me. And yeah, size is at a premium; I'm not building a MX64 quad here!

  10. #30

    Re: Numa V2 - Quad Mech

    so the pyboard is ultimately a win in the "up and running" category for me
    Got it! I'm wondering if there is an arbitrage opportunity to sell pre-made Pi/Teensy/Raspbian kits that kind-of work like Micro Python, but have higher performance. All in software!

    I'm not building a MX64 quad here!
    But maybe ... maybe you should be? :-D

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