SHOP News & Articles Contact Impressum

Unable to communicate with the AX 12 A servo motor


I am using DSC controller and trying to communicate with the Dynamixel AX12A servo motor from my RasPi 3B. I have followed the steps described in the following link

I have also configured the con.yaml file as mentioned in the above link. I am able to run the dsc.launch file and also the serial_node in rosserial_python. When I check the /mydata ros topic, all the values are -1. But I have connected a servo motor to the second slot. Can you help me with that?

I am using the ubiquity linux image for my RasPi


Dear Kumaar,

do you’ve checked if the connection between the DSC and RPi is established?
Could you please post the con.yml file here? I would like to check if you have used Tabs or Spaces for formating it. You have to use spaces, if you are using tabs the file will not work.


MYBOTSHOP Support :robot:


Here is the code inside the con.yaml file. Unfortunately I could not post file other than images.
use_lib: “true”
joints: {
j1: {id: [1]},

Yes the connection is established. I able to see the port /dev/ttyAMA0 and the Arduino IDE is able to detect the controller


Dear all,

thanks for the file content.

Could you please tell me at least step by step which commands you’ve typed into the command line?


After building the catkin project and sourcing it, I typed the following commands,

  1. roscore
  2. rosrun rosserial_python /dev/ttyAMA0
  3. rostopic echo /mydata

No data was read from the servo motor,
For all the sequence number, the output was like below
position: [-1, -1, -1, -1]
temperature: [-1, -1, -1, -1]
voltage: [-1, -1, -1, -1]


Do you have a USBasp Programmer? If so, could you please upload the DYNAMIXEL Write Example to make sure the Servomotor is working properly?

Thanks in advance :robot:


I am sorry. I do not have a USap programmer. Is there any other alternative. And for your information I have checked with 2 dynamixel motors. It did not work with neither of them.