[Custom Integration] LaCrosse JeeLink Bridge (Native 868 MHz Temperature/Humidity Sensors)

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Hi everyone,

I've got a handful of LaCrosse/TX35/IT+ temperature and humidity sensors around the house, received via a DIY JeeLink Clone USB stick, and previously relied on FHEM to get them into Home Assistant. I wanted to drop that dependency entirely and get a native, local integration instead.

I'm happy to share my native Home Assistant Custom Integration for LaCrosse/JeeLink 868 MHz sensors. It talks directly to the JeeLink stick over serial (57600 baud, OK 9 telegrams), so there's no cloud, no external APIs.

Development Background: The protocol handling is modelled closely on FHEM's proven 36_LaCrosse.pm and 36_JeeLink.pm (dew point calculation, outlier filtering, firmware quirk recovery), since that's the battle-tested reference for this hardware.

  • 100% Local: Direct serial connection to the JeeLink stick, no cloud, no FHEM.
  • Automatic Sensor Discovery: New sensors appear as devices automatically, complete with temperature, humidity (if present), and a calculated dew point (Magnus formula, same as FHEM).
  • Battery Replacement Mode: Press a per-sensor button, swap the battery within the configured window, and the sensor's new random radio ID is mapped onto the existing device — entities and history are preserved.
  • Outlier Filtering: Absolute and delta limits reject bad readings, with configurable confirmation count for genuine jumps.
  • Robust Serial Handling: DTR hardware reset and automatic recovery from known firmware hangs (drecvintr exit, RFM12 hang), with configurable reconnect delay.
  • Optional Notifications: Connection lost/restored, new sensor discovered, battery low, battery replacement detected — all via any notify entity.
  • Multilingual: Full English and German UI, including all dynamic notification texts.
  • HACS Ready: Easy to install via HACS as a custom repository.

GitHub Repository: GitHub - Lu-Fi/ha-lacrosse-jeelink

I've tested this on a JeeLink v3 as well as a DIY Arduino clone (CH340 + RFM69) flashed with the same LaCrosseITPlusReader sketch that FHEM uses, and it's been running reliably with about two dozen sensors. If you've got LaCrosse/Technoline TX25/TX27/TX29/TX35/TX37 sensors or a genuine JeeLink, I'd love to hear how it works for you.

Any feedback, suggestions, or PRs are highly appreciated!

Best regards, Lu-Fi

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I have been interested in getting the data from a LaCrosse sensor into HA.

I have two TX141TH-BV3 433MHz sensors, which won't work with your code. Or will it, if the JeeLink 433 is used?

I notice on the JeeLink website there is a JLink Classic and the JeeLink (v3c), the former having FHEM support. Which to choose?

Perhaps an Arduino Nano (compatible?) with a 433MHz RFM69? Do you have a schematic for this?

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Hi OldSurferDude,

no, the TX141TH-BV3 won’t work with this integration — not with any JeeLink and not with a DIY Arduino either. The problem isn’t the frequency, it’s the radio protocol: your sensors use a different modulation (OOK) than the LaCrosse IT+ sensors this firmware understands (FSK). The JeeLink firmware simply has no decoder for the TX141 family, so a 433 MHz version of the hardware wouldn’t change anything.

For the same reason the Classic-vs-v3c question doesn’t matter here — that choice is only relevant if you use 868 MHz IT+ sensors (TX29, TX35 etc.).

regards

LuFi