Web-based control for a SteppIR SDA 100 antenna controller and a hy-gain DCU-2 rotator controller, used by Jefferson Amateur Radio Club operators on a Flex 6300 setup. Runs on Windows 11. One computer (computer A) has the physical USB-to-serial connections to both devices; operators on the LAN (or remotely via Tailscale) connect with a browser to the steprtool web UI to issue commands.

py -m venv .venv
.\.venv\Scripts\python -m pip install -r requirements.txt
copy .env.example .env
.\.venv\Scripts\python run.py

Open https://localhost:8443/ in a browser. Your browser will warn about the self-signed certificate; accept it. Enter a name and callsign in the modal, then exercise the controls. With SDA100_PORT=MOCK and DCU2_PORT=MOCK in .env (the defaults), commands are computed and the bytes shown in the Last Action panel, but nothing is written to a serial port.

All settings live in .env. Copy .env.example and edit:

To switch a device from mock to live, change its *_PORT from MOCK to the real COM port name and restart steprtool.

SDA 100 — 11-byte fixed frame, no response from device, write-and-wait:

Home and Calibrate command bytes are not yet defined — those buttons exist in the UI and return a NOT IMPLEMENTED response with no bytes and no lock.

DCU-2 — ASCII command set shared with the DCU-1, 4800 baud, 8-N-1:

• AP1xxx; sets target bearing (xxx = 000..359, three digits zero-padded)
• AM1; starts rotation
• steprtool sends them combined as AP1xxx;AM1;

The DCU-2 does not report position back, so steprtool cannot tell when motion has finished. Instead it locks the device for DCU2_WAIT_SECONDS after each command (default 60s, the worst-case full-rotation time).

• SDA 100 panel: frequency input (kHz), buttons for Change Frequency, Home, Calibrate. Only Change Frequency requires the input.
• DCU-2 panel: azimuth input (0–359°), eight compass quick-fill buttons (N, NE, E, SE, S, SW, W, NW), Change Direction button.
• Last Action panel: device, action, operator, status, detail, bytes sent (hex). Updates in place; broadcast to all connected browsers via Socket.IO.
• Countdown timer: while a device is locked, the time remaining is shown next to that device's status. All connected browsers see the same countdown.
• Operator identification: on first visit, a modal asks for name and callsign. Stored in browser localStorage. Sent with every command and written to the log.

• Per-device lock. While one device is locked, commands to it return HTTP 409 with seconds remaining. Commands to the other device are unaffected.
• All connected clients see the same lock state and the same Last Action via Socket.IO; "last write wins" if two browsers race the same device.

• logs/steprtool.log — application log, rotated at 2 MB, 5 backups.
• logs/service.out.log / logs/service.err.log — written by NSSM when run as a service.

Every command logs operator, device, action, bytes, and status.

Install NSSM (https://nssm.cc/), put nssm.exe on PATH, then from an Administrator command prompt in the project root:

.\scripts\install-service.bat
sc start steprtool

To remove:

.\scripts\uninstall-service.bat

run.py                          entry point
.env.example                    template config
requirements.txt                Python deps
steprtool/
  app.py                        Flask + Socket.IO app factory
  config.py                     .env loader and validator
  devices/
    base.py                     lock / wait timer / serial / broadcast
    sda100.py                  SDA 100 command builder + actions
    dcu2.py                     DCU-2 command builder + actions
  routes/
    api.py                      JSON command endpoints
    pages.py                    index template route
  static/css/style.css
  static/js/app.js
  templates/index.html
scripts/
  generate-cert.py              self-signed cert generator
  install-service.bat
  uninstall-service.bat
certs/                          generated cert + key (gitignored)
logs/                           rotated logs (gitignored)