LP-700 Server

WebSocket bridge for the Telepost LP-500 / LP-700 Digital Station Monitor. One server owns the meter's USB HID handle; many clients (browsers, phones, logging PCs) get live telemetry and can issue control verbs, with every client kept in sync.

Companion of VU3ESV/LP-100A-Server. Same fan-out semantics, same WebSocket frame shape, same Pi-first deployment story — HID instead of serial.

See ARCHITECTURE.md for the design and CLAUDE.md for the LP-500/700 USB HID protocol reference.

Quick start (development, on a Mac)

go mod tidy
go test ./...
go run . -backend simulator -config deploy/config.example.toml
# open http://localhost:8089/

The reference web client is embedded in the binary — no separate frontend build step.

Building for the Raspberry Pi

./deploy/build-pi.sh                  # arm64 (Pi 3/4/5 with 64-bit OS)
ARCH=arm ./deploy/build-pi.sh         # ARMv7 (Pi Zero/1, 32-bit)

Pure Go (/dev/hidraw + sysfs on Linux), so no CGO toolchain is needed — GOOS=linux GOARCH=arm64 go build works with whatever Go you have.

Deploying on the Raspberry Pi

./deploy/redeploy.sh pi@raspberrypi.local

Self-bootstrapping: on a fresh Pi redeploy.sh creates the lp700 system user, installs the systemd unit + udev rule + default config, enables and starts the service, and runs a /healthz check. Subsequent runs only push the binary unless --service or --keep-config are explicitly used. SSH multiplexing means you authenticate once per redeploy and ssh -t lets sudo prompt interactively (or, with passwordless sudo, the deploy is silent).

./deploy/redeploy.sh pi@host --service       # also reinstall systemd unit
./deploy/redeploy.sh pi@host --keep-config   # binary only (skip toml/udev)
./deploy/redeploy.sh pi@host --restart-only  # bounce service only
ARCH=arm ./deploy/redeploy.sh pi@host        # 32-bit ARMv7 target

After install, confirm:

ssh pi@raspberrypi.local
systemctl status lp700-server
journalctl -u lp700-server -f
curl http://raspberrypi.local:8089/healthz

The udev rule matches the meter's Microchip default 04D8:0001 USB IDs (plus a fallback on the Product string "LP-500" / "LP-700"). If your meter uses different IDs, edit /etc/udev/rules.d/99-lp700.rules and run sudo udevadm control --reload-rules && sudo udevadm trigger.

CI / releases

• .github/workflows/ci.yml — go vet, go test -race, go build on every push and PR.
• .github/workflows/release.yml — runs on every push to main, i.e. every merged PR. It bumps the patch number of the highest vX.Y.Z tag, vets and tests, cross-compiles linux/{amd64,arm64,armv7} + darwin/{amd64,arm64} + windows/amd64, pushes the new tag, and publishes a GitHub Release with the binaries, SHA256SUMS, and notes auto-generated from the PRs since the previous tag. A failed test or build pushes no tag. The tag is stamped into each binary (-ldflags "-X main.version=<tag>"); lp700-server -version prints it.

For a minor or major bump, push the tag yourself; the tag push releases that version and later merges continue from it:

git tag v0.3.0 && git push origin v0.3.0

Configuration

/etc/lp700-server/config.toml:

Field	Default	Notes
meter.backend	auto	auto, hid, simulator
meter.vendor_id	0x04D8	Microchip default; 0 = match by Product string
meter.product_id	0x0001	PIC32 firmware default
meter.poll_ms	40	25 Hz; the meter pushes IN reports faster than we read them
server.listen	0.0.0.0:8089	:8089 to leave 8088 for LP-100A-Server
server.allow_control	true	Set false for a read-only port
server.max_clients	32
server.heartbeat_ms	2000
updates.check	true	GitHub new-release check — see Updates

After editing: sudo systemctl restart lp700-server.

Logging

Defaults to error so the journal stays quiet. Two ways to turn it up:

• At start time: pass -v (debug). Edit /etc/systemd/system/lp700-server.service's ExecStart.
• At runtime, no restart: open the web UI's Setup overlay and pick a level. Or hit the API directly:

  curl -s http://host:8089/api/log-level
  curl -s -XPOST http://host:8089/api/log-level -d '{"level":"debug"}'

Updates

The server tells you when a newer LP-700-Server release is out. About a minute after start, and then at most once a day while it runs, it makes one anonymous request to GitHub — GET https://api.github.com/repos/VU3ESV/LP-700-Server/releases/latest — and compares the release tag with its own version (vX.Y.Z tuples; a pre-release such as v1.0.0-rc.1 sorts below v1.0.0, and a git describe build such as v0.2.1-3-g92ace11 sorts above the tag it follows). A newer release is:

• shown as a notice at the top of the web UI — "LP-700-Server vX.Y.Z is available (running …) — release notes";
• logged once per release (journalctl -u lp700-server), whatever the log level is set to;
• reported by GET /api/update (read-only JSON: {enabled, automatic, current, update_available, latest, html_url, checked_at}).

Nothing is downloaded or installed — update the usual way (release binary, or deploy/redeploy.sh). The check runs on its own goroutine and never touches the meter or the WebSocket clients. If GitHub can't be reached it stays silent and tries again an hour later; the 24 h clock only starts after a successful answer. Nothing is written to disk, so a restart checks once more about a minute after start.

• Turn it off: [updates] check = false in config.toml, then restart the service. deploy/redeploy.sh keeps that setting when it regenerates config.toml.
• Development builds (a plain go build / go run, version dev) never check, and neither does a binary whose version has no vX.Y.Z core. deploy/build-pi.sh stamps git describe --tags --match 'v[0-9]*', and the release workflow stamps the tag.
• See the notice against the real latest release: run with LP700_SERVER_UPDATE_TEST_VERSION=0.0.1 set (ignored unless set); the first check comes a minute after start.

Diagnostic subcommands

sudo /usr/local/bin/lp700-server probe -list                          # enumerate every HID
sudo /usr/local/bin/lp700-server probe -dump                          # live raw + decoded frames
sudo /usr/local/bin/lp700-server probe -capture out.bin -duration 5s  # capture for offline analysis

These never run the WS server — they're hardware-only.

Security

There is no authentication. Anyone with network access to the listen address can read telemetry and issue control commands. This is intentional for LAN-only deployment. For remote access, front the server with Tailscale or WireGuard and bind the listen address to the VPN interface (or 127.0.0.1).

HTTP / WebSocket surface

Path	Purpose
/	Embedded reference web client
/ws	Telemetry stream + control verbs (see ARCHITECTURE.md §4)
/healthz	ok\n — for systemd / monitoring probes
/api/config	{backend, allow_control, title, version} — UI bootstrap
/api/log-level	GET / POST the running slog level (error/warn/info/debug)
/api/update	GET — cached result of the GitHub release check (see Updates)

Smoke test from the command line:

# requires websocat (brew install websocat)
websocat ws://raspberrypi.local:8089/ws
echo '{"type":"command","id":"1","action":"peak_toggle"}' | websocat ws://raspberrypi.local:8089/ws

Web client

Mirrors the LP-500/700 Power/SWR screen — Avg power, Peak power, SWR, channel pills (Auto / 1..4), range cycle, Peak/Avg/Tune buttons, alarm enable/tripped indicator.

The Waveform/'Scope and Spectrum modes are not mirrored to the web UI (the Mac client in LP-700-App renders them); the mode_step verb (still accepted on /ws) cycles the meter's on-LCD display so an operator can switch into them remotely if needed. While the meter is on the waveform or spectrum LCD page, the server emits {"type":"scope"} / {"type":"spectrum"} WebSocket frames at ~4 Hz alongside the regular telemetry stream — each carries a 320-element 8-bit array assembled from the firmware's cmd-'1'..'5' segments (see CLAUDE.md "Scope and spectrum sample buffers" and ARCHITECTURE.md §4).

Numeric alarm thresholds, callsign, coupler model, and firmware revision live in the meter's NVRAM and aren't transmitted via USB at all (confirmed by USB pcap audit — see CLAUDE.md) so those rows are absent from the UI.

Operations cheatsheet

journalctl -u lp700-server -f                                         # tail logs
sudo systemctl restart lp700-server                                   # after config change
sudo systemctl disable --now lp700-server                             # stop / disable
curl -sf http://localhost:8089/healthz && echo OK                     # health check
sudo -u lp700 /usr/local/bin/lp700-server -config /etc/lp700-server/config.toml -v
                                                                       # foreground debug run
curl -s -XPOST http://localhost:8089/api/log-level -d '{"level":"debug"}'
                                                                       # bump verbosity live

Layout

.
├── main.go                       # config -> hid -> hub -> http
├── internal/
│   ├── config/                   # TOML loader + defaults
│   ├── lpmeter/                  # HID owner, decoder, snapshot, simulator, probe
│   ├── hub/                      # WebSocket fan-out / fan-in / heartbeats
│   ├── update/                   # GitHub new-release check + /api/update
│   └── web/static/index.html     # reference web client (go:embed)
├── deploy/
│   ├── config.example.toml
│   ├── lp700-server.service      # systemd unit
│   ├── 99-lp700.rules            # udev rule (matches VID 0x04D8 PID 0x0001 + product string)
│   ├── build-pi.sh               # cross-compile from any Go-equipped host
│   ├── install.sh                # first-time install on the Pi
│   └── redeploy.sh               # subsequent updates (build + scp + restart, self-bootstraps)
├── examples/
│   └── node-red/                 # importable Node-RED flow + migration guide
└── .support/links.txt            # URLs to the external sources we decoded against

For Node-RED users coming from KD4Z's LP-500/700 HID DIRECT flow, see examples/node-red/ for a drop-in replacement that talks to /ws instead of /dev/hidraw* (output msg.payload shape is unchanged, so downstream nodes keep working).

Acknowledgements

Telepost Inc. designed and manufactures the LP-500 and LP-700. This project is unaffiliated; product names and trademarks belong to TelePost. The protocol decoding was grounded in the manufacturer's VB6 source archive (LP-500_DataLogger / LP-500_VM, downloadable from telepostinc.com), a USB pcap capture of LP-500_VM.exe driving a real meter, and KD4Z's Node-RED LP Dice and Slice parser. URLs in .support/links.txt.