Digital Loggers – ASCOM Alpaca Server for Digital Loggers ePDUs

A FastAPI-based server, implementing the ASCOM ISwitchV3 interface. Communication is via REST to the onboard TCP server of the ePDU. Uses the dlipower library.

---

Implemented ISwitchV3 capabilities as of this driver version

Property/Method	Supported
MaxSwitch	✔
CanAsync	✘
CanWrite	✔
GetSwitch	✔
GetSwitchDescription	✘
GetSwitchName	✔
GetSwitchValue	✔
MinSwitchValue	✔
MaxSwitchValue	✔
SetAsync	✘
SetAsyncValue	✘
SetSwitch	✔
SetSwitchName	✘
SetSwitchValue	✔
StateChangeComplete	✘
SwitchStep	✔

Tested on the Digital Loggers EPC7.

---

Architecture

File	Purpose
main.py	FastAPI app, lifespan, router wiring
config.py	Pydantic config models, YAML loader
config.yaml	User-editable configuration
switch.py	FastAPI router – ISwitchV3 endpoints
switch_device.py	Low-level driver
management.py	/management Alpaca management endpoints
setup.py	/setup HTML stub pages
discovery.py	UDP Alpaca discovery responder (port 32227)
responses.py	Pydantic response models
exceptions.py	ASCOM Alpaca error classes
shr.py	Shared FastAPI dependencies / helpers
log.py	Loguru config + stdlib intercept handler
test.py	Quick smoke-test script
requirements.txt	Python package dependencies
Dockerfile	Container build

---

Configuration

Edit config.yaml to match your dome setup.

Currently assumes that the user defines names that match those set via the DLI web API.

Multiple Digital Loggers switches can be registered by adding further entries under devices: with distinct device_number values.

---

Quick start

pip install -r requirements.txt
python main.py

The server starts on 0.0.0.0:6000 by default (configurable in config.yaml).

---

Smoke test

# Requires hardware connected, i.e. will move dome
python test.py

---

Docker

docker build -t alpaca-digital-loggers .
docker run -d --name alpaca-digital-loggers \
    -v ./config.yaml:/alpyca/config.yaml:ro \
    --network host \
    --env-file .env \
    --restart unless-stopped \
    alpaca-digital-loggers
docker logs -f alpaca-digital-loggers

---

ASCOM Conformance

Last tested with ConformU 4.3.0 (Build 49708.0503dc7) on 2026-05-16 (python test_conformu.py):

Device	Errors	Issues	Info	Status
EPC7_1 (Switch #0)	0	0	111	✓ PASS

Errors may be non-zero when no hardware is attached (NotConnectedException is the expected response). Issues == 0 indicates Alpaca protocol conformance.