Wireless

FED4 Wireless Capabilities and Hublink

The FED4 supports wireless connectivity via Hublink, which uses BLE to connect nodes (FED4) to a gateway, and the gateway to hublink.cloud for time sync, file uploads, and alerts. FED4 is automatically configured for hublink.cloud through the meta.json file on the SD card—no Hublink-specific code is required beyond enabling it.

Automatic configuration (meta.json)

• The meta.json schema is compatible with hublink.cloud. A hublink section configures BLE advertising and upload behavior:
  • advertise — BLE advertising name (e.g. "FED4").
  • advertise_every — seconds between advertising periods (e.g. 300).
  • advertise_for — duration of each advertising period in seconds (e.g. 30).
  • upload_path, append_path — where files go in cloud storage (e.g. /FED, subject:id).
  • disable — set true to turn Hublink off.
• subject, device, etc. in meta.json are used for metadata and paths. The same file drives both FED4 metadata and Hublink; one config, automatically applied when Hublink is enabled.

Enabling Hublink

• Set fed.useHublink = true before fed.begin(...). begin() then calls initializeHublink() (reads meta.json, starts Hublink). run() calls syncHublink() before sleep—sync is automatic each wake cycle.
• initializeHublink() — init Hublink (uses SD_CS pin); registers onHublinkTimestampReceived for RTC updates.
• syncHublink() — sets battery level, low-battery alerts, and runs hublink.sync() (advertise/connect, upload files, receive time).

What runs automatically

• RTC time sync — timestamps from Hublink update the RTC via adjustRTC().
• Low-battery alerts — battery under 20% triggers hublink.setAlert("Low Battery!") before sync.
• File uploads — log files (and meta.json) are uploaded according to upload_path / append_path when the gateway is in range.

Optional exclusion

• #define FED4_EXCLUDE_HUBLINK before #include <FED4.h> removes Hublink from the build to save code size.

Requirements: Hublink library, SD card with meta.json, gateway in range for BLE, and internet for the gateway → hublink.cloud.

See FED4_Hublink.cpp, Hublink examples, meta.json example. Full config and cloud usage: hublink.cloud/docs.