Thomas Ales [M S E]
391 lines
10 KiB
Markdown
391 lines
10 KiB
Markdown
# ThorLabs BBD203 Motor Controller Driver
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## Overview
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This directory contains a complete implementation of the ThorLabs BBD203 3-channel benchtop brushless DC motor controller driver. The driver implements the full APT (Advanced Positioning Technology) binary communications protocol as specified in the BBD203_Communications_Protocol.md document.
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## Architecture
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The BBD203 driver is split into three layers:
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### 1. Protocol Layer (`bbd203_protocol.py`)
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Low-level protocol implementation that handles:
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- Binary message construction and parsing
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- APT protocol message IDs and structures
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- Unit conversions (mm ↔ encoder counts, velocity/acceleration scaling)
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- Status bit definitions
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**Key Classes:**
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- `MessageID`: Enumeration of all APT message IDs
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- `APTMessage`: Message builder and parser for binary protocol
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- `APTProtocol`: High-level protocol interface with unit conversions
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### 2. Driver Layer (`bbd203_driver.py`)
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Complete driver implementation providing:
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- Serial communication with automatic message reception thread
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- 3-channel management (independent motor control)
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- Blocking and non-blocking move operations
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- Status monitoring with automatic updates
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- Event callbacks for move/home completion
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- Thread-safe operation
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**Key Classes:**
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- `BBD203Channel`: Represents state of a single motor channel
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- `BBD203Driver`: Main driver class for controller communication
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### 3. Stage Interface Layer (`thorlabs_stage.py`)
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Application-specific wrapper that:
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- Maps 3 motor channels to X/Y/Z axes
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- Provides simplified API for stage control
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- Integrates with the nueScan application
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- Maintains compatibility with existing UI
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**Channel Mapping:**
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- Channel 1 → X-axis
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- Channel 2 → Y-axis
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- Channel 3 → Z-axis (optional)
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## Features
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### Communication
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- Binary APT protocol over USB/RS232
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- Baud rate: 115200 (configurable)
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- Automatic message reception in background thread
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- Command/response handling with proper timeout
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### Motion Control
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- Absolute positioning
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- Relative moves
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- Velocity control
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- Immediate and profiled stops
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- Configurable acceleration
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### Position Feedback
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- Real-time position updates (encoder counts)
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- Position in mm (with configurable scaling)
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- Status bit monitoring (homing, moving, errors, etc.)
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### Homing
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- Individual axis homing
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- All-axes homing
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- Blocking or non-blocking operation
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- Completion callbacks
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### Safety
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- Interlock checking before moves
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- Error detection and reporting
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- Motion error monitoring
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- Limit switch status
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## Usage
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### Connection Methods
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The driver supports two connection methods:
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#### Method 1: Connect by Serial Number (Recommended)
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Similar to ThorLabs Kinesis library - automatically finds the USB device:
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```python
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from hardware.bbd203_driver import BBD203Driver
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# Create driver instance
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driver = BBD203Driver(encoder_counts_per_mm=20000)
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# List available ThorLabs devices
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devices = driver.list_thorlabs_devices()
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for device in devices:
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print(f"Serial: {device['serial']}, Port: {device['port']}")
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# Connect by serial number (auto-finds the port)
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driver.connect_by_serial('83123456') # Serial printed on controller
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```
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#### Method 2: Connect by Port Name
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Direct connection to a specific port:
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```python
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# Connect to specific port
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driver.connect('/dev/ttyUSB0') # or 'COM3' on Windows
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```
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### Basic Movement
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```python
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# Enable all channels
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driver.enable_channel(1, True) # X-axis
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driver.enable_channel(2, True) # Y-axis
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driver.enable_channel(3, True) # Z-axis
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# Home all channels (blocking)
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driver.home_all_channels(wait=True, timeout=60)
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# Set velocity parameters
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driver.set_velocity_params(channel=1, max_vel_mm_s=5.0, accel_mm_s2=10.0)
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# Move to absolute position (non-blocking)
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driver.move_absolute(channel=1, position_mm=10.0, wait=False)
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# Move to absolute position (blocking)
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driver.move_absolute(channel=2, position_mm=25.0, wait=True, timeout=30)
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# Move relative
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driver.move_relative(channel=1, distance_mm=-5.0, wait=True)
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# Stop motion
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driver.stop(channel=1, immediate=True)
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# Get position
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pos = driver.get_position(channel=1)
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print(f"Position: {pos} mm")
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# Get detailed status
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status = driver.get_channel_status(channel=1)
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print(f"Enabled: {status['enabled']}")
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print(f"Homed: {status['homed']}")
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print(f"Moving: {status['moving']}")
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# Disconnect
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driver.disconnect()
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```
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### Using the Stage Interface
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```python
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from hardware.thorlabs_stage import ThorLabsStage
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# Create stage controller
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stage = ThorLabsStage(encoder_counts_per_mm=20000)
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# List available devices
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devices = stage.list_devices()
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for device in devices:
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print(f"BBD203 Serial: {device['serial']}")
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# Connect by serial number (automatically enables all channels)
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stage.connect('83123456') # Serial number from controller label
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# Home all axes
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stage.home_all_axes(wait=True)
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# Move to position
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stage.move_absolute(x=10.0, y=20.0, wait=True)
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# Move relative
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stage.move_relative(dx=5.0, dy=-2.5, wait=True)
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# Get position
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pos = stage.get_position()
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print(f"X: {pos['x']} mm, Y: {pos['y']} mm, Z: {pos['z']} mm")
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# Check status
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status = stage.get_status()
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print(f"Ready: {status['ready']}")
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print(f"X Homed: {status['x_homed']}")
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# Disconnect
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stage.disconnect()
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```
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### Event Callbacks
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```python
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# Define callback function
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def on_move_complete(channel):
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print(f"Channel {channel} move completed!")
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# Register callback
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driver.register_move_complete_callback(1, on_move_complete)
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# Start non-blocking move - callback will be called when complete
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driver.move_absolute(channel=1, position_mm=50.0, wait=False)
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```
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## Configuration
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### Encoder Scaling
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The encoder resolution must be configured to match your specific motor/stage combination:
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```python
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# Example: MLS203 stage with 20,000 counts/mm
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driver = BBD203Driver(encoder_counts_per_mm=20000)
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# Example: Custom stage with 2,000 counts/mm
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driver = BBD203Driver(encoder_counts_per_mm=2000)
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```
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Common encoder resolutions:
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- **MLS203**: 20,000 counts/mm
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- **DDS220**: 2,000 counts/mm
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- **Custom**: Varies (check motor specifications)
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### Velocity and Acceleration
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Velocity and acceleration use the APT scaling formulas:
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```
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VEL_APT = EncCnt × 102.4e-6 × 65536 × Vel
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ACC_APT = EncCnt × (102.4e-6)² × 65536 × Acc
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```
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The driver handles these conversions automatically:
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```python
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# Set velocity to 5 mm/s, acceleration to 10 mm/s²
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driver.set_velocity_params(
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channel=1,
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max_vel_mm_s=5.0,
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accel_mm_s2=10.0
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)
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```
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## Integration with nueScan
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The driver is integrated into nueScan through the `ThorLabsStage` wrapper class. The connection is simplified using serial number auto-detection:
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### Connecting in the UI
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1. **Find Serial Number**: Look at the label on your BBD203 controller (e.g., `83123456`)
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2. **Enter Serial**: Type the serial number in the "ThorLABS MLS Stage Serial" field
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3. **Connect**: Click "Connect" button
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- Driver automatically finds the USB device
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- All 3 channels are enabled
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- Status updates begin
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4. **Ready**: The controller is now ready to home and move axes
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### Connection Process
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When you click "Connect":
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- The driver scans all USB ports for ThorLabs devices (FTDI VID: 0x0403)
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- Finds the device matching your serial number
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- Automatically uses the correct COM port
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- Enables all channels (X/Y/Z axes)
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- Sets default velocity parameters
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### Troubleshooting Connection
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If connection fails, a dialog will show:
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- The serial number you entered
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- List of all detected ThorLabs devices with their serial numbers
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- Helps you identify the correct serial to use
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## Protocol Details
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### Message Structure
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All APT messages consist of:
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- 6-byte header (message ID, length, destination, source)
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- Optional data packet (variable length)
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### Destination Addressing
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- `0x21`: Channel 1 (X-axis)
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- `0x22`: Channel 2 (Y-axis)
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- `0x23`: Channel 3 (Z-axis)
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- `0x11`: All channels
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- `0x50`: USB interface
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### Status Bits
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Key status bits monitored by the driver:
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| Bit | Mask | Meaning |
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|-----|------|---------|
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| HOMING | 0x00000200 | Homing in progress |
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| HOMED | 0x00000400 | Axis has been homed |
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| TRACKING | 0x00001000 | Following target position |
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| SETTLED | 0x00002000 | Position settled |
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| MOTION_ERROR | 0x00004000 | Following error exceeded |
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| MOTOR_ENABLED | 0x80000000 | Motor drive enabled |
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| IN_MOTION_FORWARD | 0x00000010 | Moving forward |
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| IN_MOTION_REVERSE | 0x00000020 | Moving reverse |
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## Troubleshooting
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### Connection Issues
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**Problem:** Cannot connect to controller
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**Solutions:**
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- Verify COM port name is correct (`ThorLabsStage.list_available_ports()`)
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- Check USB cable connection
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- Verify no other software has the port open
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- Try different baud rate (default: 115200)
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- Check device permissions on Linux
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### Homing Fails
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**Problem:** Homing timeout or never completes
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**Solutions:**
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- Increase homing timeout parameter
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- Check limit switches are functioning
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- Verify motor is enabled
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- Check for mechanical obstructions
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- Review homing parameters (direction, velocity)
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### Position Errors
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**Problem:** Reported position doesn't match reality
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**Solutions:**
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- Verify `encoder_counts_per_mm` setting matches your stage
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- Check encoder connections
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- Reset position counter if needed: `driver.cmd_set_position_counter()`
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- Verify stage is homed before moves
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### Communication Errors
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**Problem:** Commands not acknowledged or responses missing
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**Solutions:**
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- Increase serial timeout
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- Check for message buffer overflow
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- Verify automatic status updates are enabled
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- Add delays between rapid commands
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## Debug Output
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The driver provides extensive debug output:
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```
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INFO: Messages about successful operations
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DEBUG: Detailed command/response information
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ERROR: Error conditions and failures
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WARNING: Potential issues
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```
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Enable Python logging to capture all output:
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```python
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import logging
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logging.basicConfig(level=logging.DEBUG)
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```
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## Performance Notes
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- Message processing runs in separate thread (no blocking)
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- Typical command response time: 10-50ms
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- Position updates: ~10Hz when status messages enabled
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- Move completion detected via asynchronous message
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- Thread-safe for concurrent channel operations
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## References
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- **Protocol Documentation**: `BBD203_Communications_Protocol.md`
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- **APT Protocol Version**: 42.1
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- **Product Manual**: Available from Thorlabs.com
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- **Technical Support**: techsupport@thorlabs.com
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## License
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Copyright (C) 2025 Thomas Ales
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Licensed under GNU General Public License v2.0
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