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Thread: OKQ1: 4DOF MX Quad Mech

  1. Re: OKQ1: 4DOF MX Quad Mech

    Nice performances, I think I'll learn a lot from your implementation.
    So far, shuffling bytes around in Python hasn't been that fast for me (that's why I'm considering a C++ low level lib + python binding for next time I make a bot).

    This loop is only to read positions, right?
    ---
    Personal blog: http://xevel.org
    USB2AX documentation: http://xevelabs.com

  2. Re: OKQ1: 4DOF MX Quad Mech

    Is there any other scripting language that can be used for this purpose other than python?

  3. #93
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    Re: OKQ1: 4DOF MX Quad Mech

    Yes the packet pictured is close to 170hz then it is to 200hz. The rate seemed to vary quite a bit when I was doing that initial test. It is much more stable now after I made a few more tweaks on both the pc and arbotix code. Not sure where the remaining variability comes into play...

    I have been playing with reading and writing in the same loop the last two nights. I have set my node rate to 100hz and have been doing a sync read to capture all the servo's actual positions then immediately doing a sync write writing all the actual positions back into the servo's goal positions. This produced the curious behavior of being able to pose the robot like a mannequin that is quite interesting.

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    Re: OKQ1: 4DOF MX Quad Mech

    Quote Originally Posted by !!SofiaMiglani!! View Post
    Is there any other scripting language that can be used for this purpose other than python?
    For what purpose? Taking to dynamixels? I am sure you could use any language that has a serial communication library. ROS supports C++, python and Lisp.

  5. #95

    Re: OKQ1: 4DOF MX Quad Mech

    As already said, nice performance.

    Actually I wish the official implementations for ros drivers for Arbotix as well as others Arbotix Pro (and in some case USB2AX) would adopt some of these types of enhancements into the official firmware releases. For example all three of the above should support the group read (USB2AX already does).

    As I mentioned elsewhere I also think all three of these can also offload some additional stuff as well, like interpolation... But as I said I have already mentioned this before.

    As for Python? I am no Python expert, but I keep meaning to rewrite the razor IMU python implementation into C++. I just don't get how some simple function that waits on input from a serial port and then publishes that data on some topic at not that high of rate of speed should consume 20+ percent of a CPU core... Plus I think it may have create several threads as well!.

    Again Great work!
    Kurt

  6. #96

    Re: OKQ1: 4DOF MX Quad Mech

    Python is just generally bad news unless you're very, very, careful.

    The console/controller interface for Onyx 7 runs on a Raspberry Pi (old version.) Initially, I wrote it in Python / PyGame, and got 17 Hz update rate at 100% CPU. I then re-wrote it in C++ and OpenGL, and got 60 Hz update rate, at 20% CPU load.

    Python can be productive, if your goal is programmer speed rather than CPU speed, and you are very careful about performance.

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