delto_hardware¶

Unified ros2_control hardware interface for all Delto gripper models.

Note

What is ros2_control? ros2_control is a ROS 2 framework that provides a standardized way to interface with robot hardware. It separates the hardware driver (how to talk to the motors) from the controller (what commands to send). This means you can switch between different control strategies (position control, effort control, etc.) without changing the hardware driver code. Think of it as a universal adapter between your software and the gripper hardware.

Overview¶

The delto_hardware package provides a single SystemInterface plugin called delto_hardware/SystemInterface. This one plugin supports all Delto gripper models (DG-3F-B, DG-3F-M, DG-4F, DG-5F, DG-5F-S, DG-5F-S15) through model-aware configuration. The model is automatically detected from the gripper firmware when the connection is established.

How It Fits in the System¶

Your Application
    |
    v
ros2_control Controller  (e.g., JointTrajectoryController)
    |
    v
delto_hardware/SystemInterface  <-- this package
    |
    v
delto_tcp_comm  (TCP communication library)
    |
    v
Gripper Firmware  (physical hardware)

The hardware interface reads sensor data from the gripper (position, velocity, current, temperature, F/T sensors, GPIO) and sends motor current commands back to the gripper. Controllers sit on top of this interface and translate your high-level commands (e.g., “move to position 0.5 radians”) into the low-level effort commands that the hardware interface sends to the gripper.

Hardware Parameters (URDF/XACRO)¶

These parameters are configured in the URDF/XACRO file that describes the gripper hardware. They are passed to the hardware interface when it initializes.

Parameter	Description	Default
`delto_ip`	IP address of the gripper on the network	`169.254.186.72`
`delto_port`	TCP port the gripper listens on	`502`
`delto_model`	Model ID (hexadecimal). Determines joint count and motor direction	Auto-detected from firmware
`hand_type`	`left` or `right` (only for DG-5F and DG-5F-S)	`left`
`fingertip_sensor`	Enable F/T sensor data reading	`false`
`IO`	Enable GPIO reading and control	`false`

In the XACRO file, these appear like this:

<ros2_control name="DeltoGripperSystem" type="system">
  <hardware>
    <plugin>delto_hardware/SystemInterface</plugin>
    <param name="delto_ip">169.254.186.72</param>
    <param name="delto_port">502</param>
    <param name="fingertip_sensor">false</param>
    <param name="IO">false</param>
  </hardware>
  <!-- joint definitions ... -->
</ros2_control>

You typically do not need to edit these files directly. Instead, pass values as launch arguments (e.g., delto_ip:=192.168.1.100), and the launch file forwards them to the XACRO processor.

Connection Behavior¶

The hardware interface implements automatic background reconnection:

If the TCP connection to the gripper is lost (cable disconnected, gripper rebooted, etc.), a background thread attempts to reconnect at 1-second intervals, for up to 10 retries.
During reconnection, the read() and write() functions return OK with the last known data. This prevents ros2_control from deactivating the hardware interface during temporary disconnections.
You can monitor the connection status programmatically using the system/connection_status state interface:
- 1.0 = connected
- 0.0 = disconnected

To check the connection status from the command line:

ros2 control list_hardware_interfaces | grep connection_status

State Interfaces (Data You Can Read)¶

State interfaces are read-only data published by the hardware interface. Controllers and broadcasters use these to report the gripper’s current state.

Interface	Per	Description
`position`	Joint	Current joint position in radians
`velocity`	Joint	Current joint velocity in radians/second
`effort`	Joint	Current motor current in amperes
`temperature`	Joint	Motor temperature in degrees Celsius
`force.x`, `force.y`, `force.z`	Finger	Fingertip force (if `fingertip_sensor` enabled)
`torque.x`, `torque.y`, `torque.z`	Finger	Fingertip torque (if `fingertip_sensor` enabled)
`gpio/output_1`, `gpio/output_2`, `gpio/output_3`	System	GPIO output states (if `IO` enabled)
`gpio/input_1`	System	GPIO input state (if `IO` enabled)
`system/connection_status`	System	TCP connection status (1.0 = connected, 0.0 = disconnected)

Command Interfaces (Data You Can Write)¶

Interface	Per	Description
`effort`	Joint	Motor current command. This is the only command interface – all controllers ultimately output effort commands

Note

Why effort only? The Delto gripper firmware accepts motor current (effort) commands directly. Position control is implemented by the ros2_control controllers (like JointTrajectoryController) which read the current position, compute the error, and output an effort command through a PID loop. This design gives you maximum flexibility to choose or implement your own control strategy.

Services¶

The hardware interface creates several ROS 2 services for calibration and GPIO control. The service names include the gripper’s namespace.

Replace <ns> with your gripper’s namespace (e.g., dg5f_right, dg4f, dg3f_m, dg5f_s_right).

/<ns>/delto_hardware_interface_node/set_ft_sensor_offset: Type: std_srvs/srv/Trigger; Zero-calibrate all fingertip F/T sensors. Call when nothing is touching the fingertips to set the current readings as zero.
/<ns>/set_gpio_output1: Type: std_srvs/srv/SetBool; Set GPIO output 1 (true = high, false = low)
/<ns>/set_gpio_output2: Type: std_srvs/srv/SetBool; Set GPIO output 2
/<ns>/set_gpio_output3: Type: std_srvs/srv/SetBool; Set GPIO output 3

Example – calibrate F/T sensors:

ros2 service call /dg5f_right/delto_hardware_interface_node/set_ft_sensor_offset std_srvs/srv/Trigger

Example – set GPIO output 1 to high:

ros2 service call /dg5f_right/set_gpio_output1 std_srvs/srv/SetBool "{data: true}"

Supported Models¶

The hardware interface supports all Delto gripper models through a unified codebase:

Model ID	Model Name	Motors	Bytes/Motor	GPIO	Sensor
`0x3F01`	~~DG-3F B~~	12	5	Yes	–
`0x3F02`	DG-3F M	12	8	Yes	F/T, TACTILE_M
`0x4F02`	DG-4F	18	8	Yes	F/T, TACTILE_M
`0x5F12`	DG-5F Left	20	8	Yes	F/T, TACTILE_M
`0x5F22`	DG-5F Right	20	8	Yes	F/T, TACTILE_M
`0x5F14`	DG-5F-S Left	20	8	–	F/T, TACTILE_S
`0x5F24`	DG-5F-S Right	20	8	–	F/T, TACTILE_S
`0x5F34`	DG-5F-S15 Left	15	8	–	TACTILE_S
`0x5F44`	DG-5F-S15 Right	15	8	–	TACTILE_S

Control Flow¶

For those interested in the internal workings, here is the lifecycle of the hardware interface:

on_init()       -> Parse URDF parameters, establish TCP connection, create ROS 2 services
on_activate()   -> Verify connection is active
read()          -> Receive joint/sensor/GPIO data from gripper, process service callbacks
write()         -> Convert controller effort commands to motor duty values, send to gripper
on_deactivate() -> Disconnect from gripper

The read() and write() functions are called by the controller manager at the configured update rate (typically 100-300 Hz).