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Add controls for the camera orientation

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Matt Spencer
2026-04-16 21:41:48 +00:00
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@@ -1,11 +1,15 @@
# my_robot — Motor Controller Node
# my_robot
ROS 2 package for differential-drive motor control on the Yahboom Raspbot V2 platform.
ROS 2 package for the Yahboom Raspbot V2 platform — differential-drive motor control and pan/tilt camera orientation.
---
## Architecture
Both nodes share the same I²C bus. The Linux kernel serialises individual transactions, so they can run as separate processes without additional locking.
### Motor controller
```
┌───────────────────────────────────┐
│ MotorControllerNode │
@@ -28,7 +32,7 @@ ROS 2 package for differential-drive motor control on the Yahboom Raspbot V2 pla
└───────────────────────────────────┘
```
### Topics
#### Topics
| Topic | Direction | Type | Description |
|---|---|---|---|
@@ -36,16 +40,63 @@ ROS 2 package for differential-drive motor control on the Yahboom Raspbot V2 pla
| `/wheel_speeds` | Subscribed | `std_msgs/Float32MultiArray` | Direct per-wheel speed override `[FL, FR, RL, RR]` in library units (0–255) |
| `/current_wheel_speeds` | Published | `std_msgs/Float32MultiArray` | Current wheel speeds read from hardware, published at 10 Hz |
### Parameters
#### Parameters
| Parameter | Default | Description |
|---|---|---|
| `wheel_base` | `0.3` | Distance between left and right wheels in metres |
| `max_speed` | `1.0` | Maximum motor speed in library units |
### Hardware interface
---
The node drives the Yahboom Raspbot V2 motor controller over **I²C bus 1** (device address `0x2B`) using the bundled `raspbot_v2_interface` library. The only host device required is `/dev/i2c-1`.
### Camera orientation controller
```
┌──────────────────────────────────────┐
│ CameraOrientationNode │
│ │
/joint_command ────────>│ JointState (names: pan, tilt) │
(sensor_msgs/ │ position in radians │
JointState) │ │
│ pan → servo 1 (0°–180°) │
│ tilt → servo 2 (0°–110°) │
│ │
│ ▼ │
│ raspbot_v2_interface │
│ I²C bus 1, addr 0x2B │
│ ▼ │
│ /dev/i2c-1 ──────> Pan/tilt servos │
│ │
/joint_states <────────│ current angles @ 10 Hz │
(sensor_msgs/ │ position in radians │
JointState) │ │
└──────────────────────────────────────┘
```
#### Topics
| Topic | Direction | Type | Description |
|---|---|---|---|
| `/joint_command` | Subscribed | `sensor_msgs/JointState` | Commanded pan/tilt angles. Joint names `"pan"` and `"tilt"`, positions in **radians**. Unknown joint names are ignored. |
| `/joint_states` | Published | `sensor_msgs/JointState` | Current angles reflected from the last command, published at 10 Hz |
#### Parameters
| Parameter | Default | Description |
|---|---|---|
| `pan_servo_id` | `1` | Raspbot servo channel for pan |
| `tilt_servo_id` | `2` | Raspbot servo channel for tilt |
| `pan_min_deg` | `0.0` | Pan lower limit (degrees) |
| `pan_max_deg` | `180.0` | Pan upper limit (degrees) |
| `tilt_min_deg` | `0.0` | Tilt lower limit (degrees) |
| `tilt_max_deg` | `110.0` | Tilt upper limit (degrees) — hardware cap |
| `pan_center_deg` | `90.0` | Startup and shutdown park position for pan |
| `tilt_center_deg` | `60.0` | Startup and shutdown park position for tilt |
| `state_rate_hz` | `10.0` | `~/joint_states` publish rate |
#### Hardware interface
The node drives the pan and tilt servos over **I²C bus 1** (device address `0x2B`). The same `/dev/i2c-1` device used by the motor controller is sufficient — no additional device node is required.
---
@@ -126,7 +177,57 @@ docker run --rm \
If your board exposes the motor controller on a different bus (check with `ls /dev/i2c-*` on the host), substitute the correct device node (e.g. `--device /dev/i2c-0`).
### Overriding parameters at launch
### Camera orientation node
Override the default `CMD` to run the camera orientation node instead:
```bash
docker run --rm \
--network=host \
--device /dev/i2c-1 \
--env ROS_DOMAIN_ID=0 \
my_robot:latest \
ros2 run my_robot camera_orientation
```
#### Overriding parameters at launch
```bash
docker run --rm \
--network=host \
--device /dev/i2c-1 \
--env ROS_DOMAIN_ID=0 \
my_robot:latest \
ros2 run my_robot camera_orientation \
--ros-args -p pan_center_deg:=90.0 -p tilt_center_deg:=45.0
```
#### Commanding the camera from the host
Pan to centre (90°) and tilt to 30°:
```bash
ros2 topic pub --once /joint_command sensor_msgs/msg/JointState \
"{name: ['pan', 'tilt'], position: [1.5708, 0.5236]}"
```
You can command a single axis by omitting the other joint name:
```bash
# Pan only
ros2 topic pub --once /joint_command sensor_msgs/msg/JointState \
"{name: ['pan'], position: [0.0]}"
```
#### Verifying orientation state
```bash
ros2 topic echo /joint_states
```
---
### Overriding parameters at launch (motor controller)
ROS 2 parameters can be passed through `--ros-args`:
@@ -172,11 +273,14 @@ ros2 topic echo /current_wheel_speeds
.
├── Dockerfile # Two-stage production image
├── docker-entrypoint.sh # Sources ROS overlays before exec
├── package.xml # ROS package manifest
├── setup.py # ament_python build definition
├── my_robot/
│ ├── __init__.py
│ └── motor_controller_node.py
├── src/
│ └── my_robot/
│ ├── package.xml # ROS package manifest
│ ├── setup.py # ament_python build definition
│ └── my_robot/
│ ├── __init__.py
│ ├── motor_controller_node.py # Differential-drive motor control
│ └── camera_orientation_node.py # Pan/tilt servo control
└── raspbot_v2_interface/ # Vendored Yahboom hardware library
└── Raspbot_Lib/
└── Raspbot_Lib.py # I²C driver (smbus, bus 1, addr 0x2B)