Problem activating RobotiqGripperHardwareInterface

[Cavalletta98]

Hi, when i try to use the driver with a real robotiq 2F-140 connected to a UR10e without an external USB cable and with the ROS485 URCap active, i got this errors
[ros2_control_node-1] [WARN] [1746261825.413040664] [DefaultDriver]: Resending the command because the previous attempt (1 of 5) failed: IO Exception: Requested 8 bytes, but got 0, file /home/ws/src/ros2_robotiq_gripper/robotiq_driver/src/default_serial.cpp, line 62. [ros2_control_node-1] [WARN] [1746261825.912814109] [DefaultDriver]: Resending the command because the previous attempt (2 of 5) failed: IO Exception: Requested 8 bytes, but got 0, file /home/ws/src/ros2_robotiq_gripper/robotiq_driver/src/default_serial.cpp, line 62. [ros2_control_node-1] [WARN] [1746261826.412683502] [DefaultDriver]: Resending the command because the previous attempt (3 of 5) failed: IO Exception: Requested 8 bytes, but got 0, file /home/ws/src/ros2_robotiq_gripper/robotiq_driver/src/default_serial.cpp, line 62. [ros2_control_node-1] [WARN] [1746261826.912489852] [DefaultDriver]: Resending the command because the previous attempt (4 of 5) failed: IO Exception: Requested 8 bytes, but got 0, file /home/ws/src/ros2_robotiq_gripper/robotiq_driver/src/default_serial.cpp, line 62. [ros2_control_node-1] [WARN] [1746261827.412284725] [DefaultDriver]: Resending the command because the previous attempt (5 of 5) failed: IO Exception: Requested 8 bytes, but got 0, file /home/ws/src/ros2_robotiq_gripper/robotiq_driver/src/default_serial.cpp, line 62. [ros2_control_node-1] [ERROR] [1746261827.412331835] [DefaultDriver]: Reached maximum retries. Operation failed. [ros2_control_node-1] [FATAL] [1746261827.412469339] [RobotiqGripperHardwareInterface]: Failed to communicate with the Robotiq gripper: DriverException: Failed to deactivate the gripper..
Does someone knows why?

[frankWang67]

I've met the same problem with USB connection and fixed it. I don't know whether it works for the URCap situation, but I'd like to share my solution for those who encoutered with this problem to have a try.

The reason might be incorrect slave_address. The default slave_address is 9, hard-coded in the driver codes. You can use mbpoll to find out your correct slave address:

sudo apt install mbpoll
mbpoll -m rtu -a 9 -b 115200 -P none -t 3 -r 1000 /dev/ttyUSB0

Since 9 is incorrect, it should output:

-- Polling slave 9... Ctrl-C to stop)
Read input register failed: Connection timed out
-- Polling slave 9... Ctrl-C to stop)
Read input register failed: Connection timed out
-- Polling slave 9... Ctrl-C to stop)
Read input register failed: Connection timed out
-- Polling slave 9... Ctrl-C to stop)
Read input register failed: Connection timed out
^C--- /dev/ttyUSB0 poll statistics ---
4 frames transmitted, 0 received, 4 errors, 100.0% frame loss

Then you can change the value after -a to look for the correct slave address. For me, it's 2:

-- Polling slave 2... Ctrl-C to stop)
[1000]: 	0
-- Polling slave 2... Ctrl-C to stop)
[1000]: 	0
-- Polling slave 2... Ctrl-C to stop)
[1000]: 	0
-- Polling slave 2... Ctrl-C to stop)
[1000]: 	0
-- Polling slave 2... Ctrl-C to stop)
[1000]: 	0
-- Polling slave 2... Ctrl-C to stop)
[1000]: 	0
^C--- /dev/ttyUSB0 poll statistics ---
6 frames transmitted, 6 received, 0 errors, 0.0% frame loss

After finding the correct slave address, you can modify line 45 of robotiq_driver/src/default_driver_factory.cpp from:

constexpr uint8_t kSlaveAddressParamDefault = 0x09;

to:

constexpr uint8_t kSlaveAddressParamDefault = 0x02; // change it to your correct slave address

Then go back to the workspace and colcon build again, it should work now!