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Thread: Using Bioloid Library With Servo Modes

  1. Using Bioloid Library With Servo Modes

    Good Morning

    I was hoping someone else has run into this issue, and possibly had some insight. I want to run three Mx-Servos, in each mode available. ie)

    Servo_1 in Wheel_Mode
    Servo_2 in Joint_Mode
    Servo_3 in Multi_Turn_Mode

    The bioloid library seems to ignore everything when I attempt to Interpolate any Flash poses. Of course it has no issues if I directly command it with ax12 library, I was just hoping to use the smooth scaling of pose interpolating if it was possible.

    Also I was hoping I could find out if there was a way to use the LoadPose with an array that is not loaded into flash? Paving the way for small changes to be made in the array, before it gets loaded into the pose buffer.

    Trevor

  2. #2

    Re: Using Bioloid Library With Servo Modes

    Never tried it... Don't have MX servos... Mostly in past AX12s and now XL430-w250...

    But Bioloid library. I don't think the functions like setNextPose, or loadPose do anything to set modes.

    All these functions do is: Once you setup the next pose it simple does:
    Calculate how much each servo should move per time frame, mine set to 33ms or about 30 frames per second.
    So if the current position of the servos was at 1000 and you want to move it to 200 in 1 second.
    Each time period it will move that servo: (2000-1000)/30 or about 33.33 units per 33ms...

    So at each cycle time, it increments the table of servos with the delta for each servo and then does a SYNC Write of the two bytes for new Goal Position for each of the servos in that table....

    So does setting the GOAL_POSITION value work in the other modes?

    Also The pose code does some stuff to add to the resolution stuff. That is if you were only moving from 10 to 20 and the time you specified was 40 cycles... then (20-10)/40 does not work well...

    So they take the positions and << BIOLOID_SHIFT to give larger numbers and as such larger delta. I Think the default is BIOLOID_SHIFT=3. Which works OK in joint mode with MX as the range of values is 0-4095 and if you
    do 4095<<3 = 0x7ff8 (32760) which still fits into a 16 bit integer...

    However if you are in multi-turn mode with values > 4095, then they may not fit into the 16 bit integers after begin shifted...

  3. Re: Using Bioloid Library With Servo Modes

    Thanks for the reply KurtEck

    The modes are set using the ax12 library easily enough, there are macros already built for it. I tried it again today, without the wheel mode servo in the mix, just the joint and multi_turn, it still will not work. If I change them all to joint mode, they work fine. I am guessing it just was not written with the extended values in a 6 bit, as you said!!

    After I had the three working in unison with Bioloid, I attempted to use an array in the variable context instead of the const uint16_t PROGMEM form (loaded into flash as a constant, and therefore unchangeable) to see if it would be possible to update a field in the array. It was having none of that. I was able to update and verify that it actually did update through serial, however bioloid would not accept it until it was loaded into flash as a const.

    It looks like I will have to do similar to what you have done and break out the frame movements using syncWritePosition. I haven't given up yet though...

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