Focuser Device - aaronwmorris/indi-allsky GitHub Wiki
Mechanical Focusers
indi-allsky supports electronic focuser mechanisms to automate and fine-tune lens optical focus directly from the web interface or via command-line utilities.
Focusers are configured in the web interface under Configuration → Focuser.
1. Supported Focuser Hardware
| Driver Class | Supported Controller / Motor | Interface | Typical Pin Configuration |
|---|---|---|---|
focuser_28byj |
28BYJ-48 Stepper with ULN2003 Driver | 4 GPIO Pins | Pin 1: IN1, Pin 2: IN2, Pin 3: IN3, Pin 4: IN4 |
focuser_a4988 |
A4988 / DRV8825 with NEMA 14 / NEMA 17 | 2–3 GPIO Pins | Pin 1: STEP, Pin 2: DIR, Pin 3: MS1 (Optional half-stepping) |
focuserMotorKit |
Adafruit Motor Shield / Motor FeatherWing (PCA9685) | I2C (0x60) |
stepper1 or stepper2 channel |
focuserSerial28byj |
Arduino / Custom Serial Microcontroller | USB / Serial | Serial device path (e.g. /dev/ttyUSB0 or /dev/ttyACM0) |
focuserSimulator |
Software Simulation Driver | Software | Virtual device for interface testing |
2. Wiring & Controller Details
28BYJ-48 Stepper with ULN2003 Driver
The 28BYJ-48 is an inexpensive 5V geared unipolar stepper motor (most commonly 1:64 reduction ratio) driven by a ULN2003 Darlington transistor array:
- Connect 5V and GND to the board power rail.
- Connect IN1, IN2, IN3, and IN4 to four available GPIO pins (e.g.,
D17,D18,D27,D22). - Ensure appropriate GPIO Permissions are granted to the
indi-allskyservice user.
A4988 / DRV8825 Bipolar Stepper Driver
For higher-torque NEMA 14 or NEMA 17 stepper motors:
- STEP: Pulses motor position (1 pulse = 1 step).
- DIR: Logic level sets clockwise or counter-clockwise rotation.
- MS1 / MS2 / MS3: (Optional) Microstepping selection pins.
Adafruit MotorKit (I2C)
The Adafruit Motor Shield uses I2C communication (default address 0x60).
[!WARNING] If utilizing the Adafruit MotorKit for both focuser control and dew heaters/fans, ensure that I2C bus concurrency conflicts do not occur between the capture process and web worker processes.
3. Web Interface Focus Calibration
In the web interface:
- Navigate to Tools → Focus Assistant.
- Select target step increments (
1,10,50,100steps) and direction (In / Out). - Inspect live star metrics (FWHM, HFD, and SEP star counts) as focus position varies to identify the critical focus zone.