KKM S5-BCN

Reference for the KKM S5-BCN temperature/humidity/motion sensor

Overview

The S5-BCN temperature, humidity, and motion sensor is a Blecon device made by KKM and distributed by Blecon. The S5-BCN comes ready to connect to your Blecon network. The S5-BCN is IP67-rated and suitable for use in wet/humid environments.

The pre-installed firmware is fully open-source and includes built-in support for Memfault OTA update. This means you can easily make modifications and customisations to the pre-installed firmware and deploy them without having to physically flash the hardware.

Hardware

System

Processor / SoC	Nordic nRF52833
External SPI Flash	512KB
Temperature and Humidity Sensor	Sensirion SHT40
Motion Sensing	ST LIS3DH
LED	1x Red (inside enclosure)
Input	1x Tactile Switch (inside enclosure)
Battery	CR2477

Physical

Dimensions	38mm diameter x 12 mm height
Weight	24g
Environmental	IP67

Pre-installed Firmware

The firmware that is pre-installed on the S5-BCN logs humidity and temperature readings every minute as well as sudden motion events. The S5-BCN attempts to submit logged data via Blecon requests every 5 minutes. The pre-installed firmware also comes with Memfault support built-in and is ready to connect to a Memfault account to enable OTA update.

If you need to customise the behaviour of the S5-BCN, the Zephyr-based firmware for the S5-BCN is fully open source and available from the Blecon GitHub repository.

Receiving data from the S5-BCN

The S5-BCN submits logged data to the Blecon network and the messages it sends can be connected to any integrations you have set up on your network.

Data from the S5-BCN arrives as events with the namespace kkm_s5_bcnand with the method log

A typical log report payload from the S5-BCN has the following structure (after decoding):

{
    "uptime": 305,
    "battery": 2950,
    "events": [
      {
        "id": 123
        "time": "2025-01-21T22:00:02+00:00",
        "type": "temperature_humidity_update",
        "temperature": 25.82,
        "humidity": 49.05
      }
    ]
}

Field	Description
uptime	device uptime in seconds
battery	device battery voltage in mV
events	list of logged temperature and motion events

Events

Field	Description
id	ID to disambiguate events
time	timestamp of the event
type	temperature_humidity_update , motion_start, motion_stop, or motion_vector

Temperature/Humidity Updates

Field	Description
temperature	Temperature in °C
humidity	% Relative humidity

Motion events

• motion_start - time movement started

• motion_stop- time movement ended

• motion_vector- (x, y, z) acceleration vector of resting position

Memfault Setup and OTA

To connect S5-BCN devices with Memfault, follow the instructions in the Memfault Integration guide. Use the default namespace of memfault.

When building new versions of the firmware for OTA, the firmware needs to be configured with and uploaded to Memfault with the following scheme:

Configuration Field	Value
Software type	main
Hardware version	kkm_s5_bcn
Software version	major.minor.patch with optional pre-release and metadata suffixes. Example: 3.3.2+sensor-memfault-metrics

Alternative firmware variants

The Blecon firmware repository contains alternative firmware variants for the S5-BCN. These can be built and directly flashed onto the hardware or deployed using OTA.

The sensor-memfaultvariant of the firmware exercises more of Memfault's metric capturing and crash reporting features. For instance this variant allows a flag to be set to cause the firmware to crash.