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Home > Troubleshooting > The power port of the 3F gripper seems to have serial pins, but do they work?
Mohamed_Raessa

Hello Robotiq community, 

We got a ROBOTIQ 3F gripper, and I am trying to figure out the communication connection. If possible, I want to use only one cable for power and communication. After reading the manual, this does not seem to be possible, but I wanted to confirm with you.

The manual says that the RS485 serials pins (inside the power connecter) are UNUSED. I highlighted it. 

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Just for confirmation, does this mean those pins can not be used for communication, and another dedicated cable is needed? 

If the answer is yes, will the best option be the Ethernet, or is USB equivalent to it? 

I am looking forward to your reply. Thanks! 

Best regards,
Raessa 
bcastets

When you buy the 3F you can choose the communication protocol.

If you have the Modbus TCP version for example, you can control the gripper via ethernet thought the communication cable provided with the gripper using Modbus TCP protocol.

It is also possible to control the gripper using the RS485 wires of the power cable and communicate using modbus RTU.

For trouble shooting it is possible to use the USB port of the gripper to connect the gripper on the USB port of your PC and control is with robotiq user interface software.
Mohamed_Raessa

Thank you, @bcastets 

I knew that the selected communication protocol at the purchase was Modbus RTU. The gripper works with a USB cable with Robotiq User Interface software on Windows. I want to control the gripper using ROS. Are you are of a ROS package that can be used with the Modbus RTU connection? 

If not, please guide me to any C++/Python SDK for that purpose, and I will do the ROS part. Thanks again! 
Mohamed_Raessa

I found your Python code @bcastets
https://github.com/castetsb/pyRobotiqGripper

Does it also work with the 3F gripper? Is there a C++ alternative for that? 
bcastets

All 3F have modbus RTU communication available but most of the time modbus TCP or other ethernet protocol are used to control the gripper.

We have a ROS package to controller the 3F with Modbus TCP:
http://wiki.ros.org/robotiq_3f_gripper_control?distro=kinetic

Here is tutorial to make it works:
http://wiki.ros.org/robotiq/Tutorials

If this ROS package does not fit your need you can eventually write your own package. The 3F can be controlled by reading and writing its registers. You can find more information about it in its manual:
https://assets.robotiq.com/website-assets/support_documents/document/3-Finger_PDF_20210617.pdf


Mohamed_Raessa

Thanks, @bcastets for your help. 

I started writing a C language Modbus RTU interface for my ROS nodes. I can confirm that till the time of writing, I can connect to the gripper, initialize it, and read the holding register. However, when I tried to open/close the gripper, I found that the same values were written to the registers, but some Action registers should be set first. Is my understanding correct? 

In the next screenshot from the manual, you shared, pages 50-51. 

zoom
It will be a great help if you explain the steps that should be done because I am not getting that (especially the yellow-highlighted part in the table). Please feel free to write something in Python or a Pseudocode. 

Thanks again!