By default, every Dynamixel servomotor has its ID set to 1. To use several servomotors in a serial way, each of them must have a unique ID.
This is the prefered solution, but it implies that you have a ready-to-use Odroid or Raspberry Pi board, connected to the network, with ipython notebook server started (or a webapp to start the server).
Connect to your robot's jupyter server by entering the URL poppy.local:8888
There are two devices allowing you to connect your Dynamixel bus to your computer: USB2Dynamixel and USB2AX.
The first one is created by Robotis (the conceptors of the Dynamixel devices) and can be used to control RS-232(serial), RS-485 (4-pin) and TTL (3-pin) busses. Be sure to set the selector in the position corresponding to the protocol you want to use. More info
USB2AX is a miniaturized version of the USB2Dynamixel able to control only TTL busses. We are using USB2AX to the rest of the doc.
- Due to differences in sensibilities, new MX-28 and MX-64 servos communicate at a 57600 baudrate with USB2AX and 57142 for USB2Dynamixel.*
USB2AX is the device that will connect the Poppy Humanoid robot’s head to the Dynamixel servomotors. It can also be used to control the servomotors directly from your computer and that’s what we will do to address the motors.
On Linux, no installation is needed, but you must add yourself in the group which own the USB serial ports. It is "dialout" or "uucp" depending on your distribution:
sudo addgroup $USER dialout
sudo addgroup $USER uucp
Otherwise, the driver is available here.
Don’t forget to power up your motors (using a SMPS2Dynamixel) otherwise they won’t be detected !
Use one of the two following software to access the Dynamixel servomotors registers:
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Herborist: tool created by the Poppy Project team.
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Dynamixel Wizard: windows-only tool provided by Robotis.
Herborist comes with the Pypot library, but needs the additional library PyQt4 for graphical interface (sudo may not be needed).
sudo apt-get install python-qt4 python-numpy python-scipy python-pip
sudo pip install pypot
It should then be directly accessible in a terminal:
herborist
Connect each motor one by one to the USB2AX and use the ’scan’ button in Herborist or Dynamixel Wizard to detect it. If it’s a new motor, it should have ID 1 and baudrate 57600bps, apart from AX-12A servos who already have a 1000000 baudrate.
You have to set:
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ID corresponding to the naming convention
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Baudrate to 1 000 000 bps
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Return delay time to 0 ms instead of 0.5 ms
In Herborist, don’t forget to click on the ’Update EEPROM’ button so the changes are taken in account.
If you want your software object to correspond to your robot without having to modify the configuration file, you should stick to the robot naming and addressing convention, described in the assembly doc and in each robot's library. This will ensure that, in your code, when you use a motor’s name, you will really send orders to the corresponding physical motor.