ble-sensor

BLE Sensor — Real IoT Application

A complete IoT sensor node that reads temperature from an I2C sensor, computes a CRC checksum, and advertises the data over BLE. This example demonstrates how multiple EoS modules work together in a real application.

What it demonstrates

• BLE initialization, advertising, and data transmission
• I2C sensor communication (read temperature register)
• CRC32 checksum computation for data integrity
• Kernel task creation for periodic sensor sampling
• GPIO LED toggle for activity indication

Modules used

Module	Header	Functions
HAL Core	eos/hal.h	eos_hal_init, eos_gpio_init, eos_gpio_toggle
HAL I2C	eos/hal.h	eos_i2c_init, eos_i2c_read_reg
HAL BLE	eos/hal_extended.h	eos_ble_init, eos_ble_advertise_start, eos_ble_send
Kernel	eos/kernel.h	eos_kernel_init, eos_kernel_start, eos_task_create, eos_task_delay_ms
Crypto	eos/crypto.h	eos_crc32

Hardware

• MCU: nRF52840 (or any BLE-capable MCU)
• Sensor: I2C temperature sensor (TMP102, LM75, or similar) on I2C port 0
• LED: Connected to pin 13

How to build

# Cross-compile for nRF52
cmake -B build \
  -DCMAKE_TOOLCHAIN_FILE=../../toolchains/arm-none-eabi.cmake \
  -DEOS_PRODUCT=iot
cmake --build build

# Host build (simulated peripherals)
cmake -B build -DEOS_PRODUCT=iot
cmake --build build
./build/ble-sensor

Expected output

[ble-sensor] BLE advertising as 'EoS-Sensor'
[ble-sensor] Sensor task started
[ble-sensor] Starting kernel...
[ble-sensor] TX seq=0 temp=23.50°C crc=0xa1b2c3d4
[ble-sensor] TX seq=1 temp=23.56°C crc=0xe5f6a7b8
...

Data format

The BLE advertisement payload is a sensor_packet_t:

Field	Type	Description
temperature_x100	int16_t	Temperature in 0.01°C units (2350 = 23.50°C)
sequence	uint32_t	Monotonic packet counter
crc	uint32_t	CRC32 of the preceding fields