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Thread: Robotis OpenCM9.04 need help.

  1. #1

    Robotis OpenCM9.04 need help.

    We have bought 6 MX 64T and a CM9.04B.


    We are totally new to these products and need technical help on controlling them.



    Here is a brief description on what we did with the motor and controller.


    One TTL port of the motor was connected to the TTL port available on the controller.
    An example code on the software was uploaded. On the other port available on the motor, we had connected a 12v DC battery with the positive wired to the pin 2 and the ground wired to the pin3 and pin 1 was left free. A red light on top of the motor lighted up for a moment and got switched off. We tried powering up the motor through the controller using the + and - pins instead of powering the motor directly. That also gave the same result.


    When we tried reading the values on the RAM of the motor, every memory location gives the same output, that is, 255.


    Expecting an early and positive reply from your side.

  2. #2
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    Re: Robotis OpenCM9.04 need help.

    Having the LED flash once at power up is perfectly normal operation. The reason you cannot access the servos is likely because you are using the default baudrate of the CM-904 and AX servos (1 Mbps), while the MX servos have a default baud of 57600 bps. You will need to open the DXL device at the slower baudrate and test reading the address table. If it works, then you can change the baudrate to the higher speed by writing to the appropriate location in the address table.

    http://support.robotis.com/en/techsu...tor_Address_04
    The baudrate address is 4 and the default value for the MX-64 is 34, while the default value for AX-12 is 1. Be very careful that you do not change the baudrate to an uncommon value, or you may require a USB2Dynamixel to reset it.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh

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    Re: Robotis OpenCM9.04 need help.

    Since you are completely new I'm assuming you haven't even set the ID's on each servo, thus they are all set to 1. Unplug all of them except one and get it going. Then set the ID's one at a time when you have a handle on how these work and are confident on how to work with the CM-904.

  4. #4

    Re: Robotis OpenCM9.04 need help.

    Thanks for your time.

    I tried connecting just one MX 64T and I suppose, it has a default ID of 1. But, still, it isn't working. Anyways, I have to check with the baud rate issues. What could be the other possible reasons?

    Thank you in advance

    Hari

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    Re: Robotis OpenCM9.04 need help.

    What code are you referring to? It will help us help you.

  6. #6

    Re: Robotis OpenCM9.04 need help.

    Thanks for your time.

    Quote Originally Posted by tician View Post
    You will need to open the DXL device at the slower baudrate and test reading the address table.
    What does the above sentence mean and how am I supposed to change the baud rate of the controller? How am I supposed to OPEN the DXL device?

    Thank you in advance

    Hari

  7. #7

    Re: Robotis OpenCM9.04 need help.

    The examples code available on the IDE provided with the controller

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    Re: Robotis OpenCM9.04 need help.

    Quote Originally Posted by Hari View Post
    Thanks for your time.



    What does the above sentence mean and how am I supposed to change the baud rate of the controller? How am I supposed to OPEN the DXL device?

    Thank you in advance

    Hari
    Tician means initialize the bus at the default baud rate of the MX-64. The CM-904 defaults to 1 Mbps, while the MX servos have a default baud of 57600 bps.
    Last edited by KevinO; 03-04-2014 at 06:59 PM.

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    Re: Robotis OpenCM9.04 need help.

    Also give us a heads up if you are new to programming. We are probably short handing our answers and might not make sense if you are just starting out.

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    Re: Robotis OpenCM9.04 need help.

    Apparently the github version of the IDE as two sketches just for this occasion ("File->Examples->06. Dynamixel" named "d_Dxl_ID_Change" and "e_Dxl_Bps_Change"). Basically, upload this sketch to the CM-904 and connect one servo, let the sketch run until the servo starts panning back and forth. After it is moving, you disconnect everything, change the desired ID number in the sketch and re-upload to the CM-904, and repeat the process for the next servo.

    YOU MUST CONNECT ONLY ONE SERVO AT A TIME TO THE CM-904. IT USES THE BROADCAST ID, SO ALL SERVOS ON THE BUS WILL CHANGE THEIR BAUDRATE AND ID TO THE SAME VALUE.
    Code:
    Dynamixel Dxl(1); //Dynamixel on Serial1(USART1)
    
    void setup() {
      // Initialize the dynamixel bus:
      Dxl.begin(34);  //57600bps
    
      Dxl.writeByte(0xfe, P_ID, 1); //Change dynamixel ID #1 (argument #3 is desired ID number)
      Dxl.writeByte(0xfe, P_BAUD_RATE, 1);  // Set baudrate to 1 Mbps
    
      // Re-initialize dynamixel bus at 1Mbps
      Dxl.begin(1);  // initialize again at new baudrate 1Mbps  
    }
    
    void loop() {
      delay(500);              // Wait for 0.5 second (500 milliseconds)
      Dxl.writeWord(1, P_GOAL_POSITION_L, 512); // Rotate dynamixel ID 1 to position ~45 degrees
      delay(500);              // Wait for 0.5 second 
      Dxl.writeWord(1, P_GOAL_POSITION_L, 3584);// Rotate dynamixel ID 1 to position ~315 degrees
    }
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh

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