Wanderer Snowflake Filter Wheel

Overview

The Wanderer Snowflake is a motorised electronic filter wheel available in two versions:

Model	Clear aperture	Supported filters
WSFW368	36 mm	up to 8 positions
WSFW508	50 mm	up to 8 positions

The wheel communicates via a USB-to-serial interface (CDC) using a simple numeric command protocol at 19200 baud, 8N1. The device continuously streams its status over the serial port, which the driver uses to track position without any dedicated polling command.

Features

• Supports both WSFW368 (36 mm) and WSFW508 (50 mm) variants
• Up to 8 filter positions per wheel
• Strict model validation — only a WSFW368 or WSFW508 is accepted; a different Wanderer Astro device on the selected port is rejected
• Model & firmware display — the model (WSFW368/WSFW508) and firmware version are read at handshake and shown in the read-only Device Info property
• Automatic calibration sent at every connection (mirrors the official Wanderer ASCOM driver behaviour)
• Zero-position detection (mechanical home to filter 1) accessible from the INDI control panel
• Per-filter name and focus offset storage on the device (configurable via the protocol)
• Device ID read/write (0–10) to distinguish several wheels on the same host
• Continuous status stream parsed in real time — current filter position is known at all times
• Firmware requirement — firmware ≥ 20260124 is required
• Full simulation mode for testing without physical hardware

Requirements

• Wanderer Snowflake filter wheel (WSFW368 or WSFW508)
• USB cable (the wheel appears as a CDC serial port, typically /dev/ttyUSB0)
• 12 V DC power supply connected to the wheel (required for motor movement)

Connection

1. Connect the wheel to your computer via USB and ensure the 12 V power supply is plugged in.
2. In KStars / Ekos, open the Equipment Profile and add Wanderer Snowflake Filter Wheel under Filter Wheel.
3. Select the correct serial port (e.g. /dev/ttyUSB0) in the Connection tab.
4. Click Connect.

On successful connection the driver will:

• Verify the model is WSFW368 or WSFW508 and that the firmware is ≥ 20260124.
• Read the current filter position, per-filter names, focus offsets and device ID from the status stream.
• Populate the Device Info property with the model and firmware version.
• Send the automatic calibration command (1500002) so the next filter movement performs a self-calibration pass.

NOTE

If the 12 V power supply is not connected the wheel will accept commands but will not move. The status stream will still be available.

IMPORTANT

If the wrong serial port is selected and the attached device is not a Snowflake (for example a Wanderer FilterCube or another Wanderer Astro device), the driver refuses to connect and reports a model mismatch instead of silently taking over the wrong device.

Operation

Changing filters

Select the target filter in the Filter Slot field (1–8) or use the Filter tab in Ekos. The driver sends the move command (200X) and monitors the continuous status stream until the wheel reports the target position.

Filter names and offsets

Filter names and focus offsets can be set in the Filter tab of the Ekos equipment manager. Each name is stored on the device as a single letter in the range B–Z (letter A is reserved by the protocol as the field delimiter). Invalid entries are rejected and the previous value is restored. Offsets are stored on the device as integer values (0–255).

Calibration

Two calibration actions are available in the Calibration group on the Main Control tab:

Button	Protocol command	Description
Auto calibrate	1500002	Flags the device so the next filter movement performs an automatic calibration pass (incremental, typically < 5 s overhead).
Zero detection	1002	Drives the wheel to its mechanical home position (filter 1), then stops. Use this if the wheel loses synchronisation.

Auto calibrate is also sent automatically at every connection, matching the behaviour of the official Wanderer ASCOM driver.

Troubleshooting

Symptom	Likely cause	Fix
Failed to read status / model mismatch at connect	Wrong port, or a different Wanderer Astro device is attached	Select the correct serial port for the Snowflake
Firmware is outdated	Firmware < 20260124	Update the firmware to the latest version
Wheel does not move	12 V not connected	Connect the power supply
Filter position shown as wrong number after startup	Partial status frame received during resync	Disconnect and reconnect; the driver re-reads the status stream
Timed out waiting for filter wheel to reach target	Very slow move (calibration pass) or mechanical obstruction	Wait and retry; run Zero detection to home the wheel

Issues

• Filter names use a single letter (B–Z) per position. Letter A is reserved by the protocol as the field delimiter and is rejected; the previous value is restored.