Sensor Logger
Demonstrates how to log timestampped sensor data and transmit this data when connectivity is available
Overview
The Sensor Logger example periodically measures temperature, humidity, and watches for motion events (sudden motion in any direction). This information is stored in a on-device journal in RAM for later transmission. It can be beneficial to store data and transmit it in batch if connectivity to the network might not always be available or to reduce power consumption as the cost of establishing a connection to the network is amortised across many sensor readings.
On devices with multiple LEDS, the application can be configured to provide visual feedback of the sensor reading. LEDs can be configured to light up when the measured temperature is rising and falling. Also, an LED can be used to show when the device is connecting to the Blecon network.
Source Code
The source code for this app is provided in the sensor-default directory of the blecon-oem-device-firmware repository: https://github.com/blecon/blecon-oem-device-firmware/tree/main/apps/sensor-default
Supported Devices
This code supports the following Zephyr board types:
Configuration Options
Configurations for each board type is found in the configuration sub-directory.
Sensor Measurement and Reporting Frequency
SAMPLING_PERIOD_SEC- Configures how frequently the device takes readings from sensors. Defaults to 60s.REPORTING_PERIOD_SEC- Configures the maximum frequency with which the device submits logged data to the cloud. If connectivity is not available when the device requests a connection, the device will continue to request
LED mapping
LED mappings are configured in the app.overlay file for the selected board under the chosen node. In the example, the blecon-led-sampling-1 and blecon-led-sampling-2 properties point to an LED device to select when the temperature is dropping or rising, respectively.
The blecon-led-status property can be assigned to an LED device to configure the LED used to show Blecon status like whether the device is announcing its ID and connected to Blecon.
Blecon LED Status Library
To display Blecon connection status on LEDs, the BLECON_LED_LIB option must be enabled. For devices with limited memory, this library can be disabled to reduce the application's memory footprint.
Receiving Data
The application 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 arrives as events with the namespace sensor and with the method log
A typical log report payload from a device 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
}
]
}uptime
device uptime in seconds
battery
device battery voltage in mV
events
list of logged temperature and motion events
Events
id
ID to disambiguate events
time
timestamp of the event
type
temperature_humidity_update , motion_start, motion_stop, or motion_vector
Temperature/Humidity Updates
temperature
Temperature in °C
humidity
% Relative humidity
Motion events
motion_start- time movement startedmotion_stop- time movement endedmotion_vector- (x,y,z) acceleration vector of resting position
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