No Response received from the remote unit/Unable to decode response

[Aruen24]

[WARN] [1731057089.221400004] [robotiq_2f_85_controller_node]: Waiting for robotiq connection...
[INFO] [1731057090.222165911] [robotiq_2f_85_controller_node]: Connected to robotiq gripper!
ModbusIOException occured!
Modbus Error: [Input/Output] Modbus Error: [Invalid Message] Incomplete message received, expected at least 2 bytes (0 received)
ModbusIOException occured!
Modbus Error: [Input/Output] No Response received from the remote unit/Unable to decode response
ModbusIOException occured!
Modbus Error: [Input/Output] No Response received from the remote unit/Unable to decode response
ModbusIOException occured!
Modbus Error: [Input/Output] No Response received from the remote unit/Unable to decode response
ModbusIOException occured!
Modbus Error: [Input/Output] No Response received from the remote unit/Unable to decode response
ModbusIOException occured!
Modbus Error: [Input/Output] No Response received from the remote unit/Unable to decode response

[harumo11]

@Aruen24 I have get same error.
In my environment, in addition to the error message, the LED is flashing red and blue. Have you found a solution?

[noskiper-chwy]

I had same issue. Fixed it by the following:

First, install Robotiq 2f URcap on the teach pendant. Then I went to Tool I/O and set 'Controlled by' to the Robotiq option. This makes it so that when going to Installation -> URCaps and clicking on the Robotiq gripper option, you should be able to activate the gripper. This should move the gripper, but obviously we need the driver to launch and we want to move the gripper with ROS2, so this doesn't solve much. But this is important for the next step which fixes the issue.

Next, what you need to do is change the ID of the gripper on the pendant. This is the little number next to the gripper in the same window we were in and it opens a dropdown. You need to change this from whatever it is (either 2,3,or 4 I'm guessing) to 1. Basically because this grippers ID was wrong, the Unit ID in the robotiq node we were trying to launch above to get the driver launched didn't match up to it.

In robotiq_modbus_server.py, if you changed line 10 trying to debug the issue, change it back to:
def init(self, unit_id = 0x0009, input_addr = 0x03E8, output_addr = 0x07D0):

Now, with the teach pendant setting the gripper ID to 1 and the Unit ID being 0x0009 (important), we are all set. You need to remove the Robotiq 2f URcap from the URCaps which will cause you to restart the pendant. Obviously, you need the rs485 urcap for this to work so I assume you have that installed on the pendant already. Then, simply follow the read me to launch the UR driver then launch the robotiq driver like before and it will not error anymore! Light should finally turn blue.

Hope this helps someone in the future!