BME280 Platform-Agnostic C++ Driver

A high-performance, zero-allocation C++17 driver for the Bosch BME280 humidity, pressure, and temperature sensor. This project demonstrates modern embedded software practices such as hardware abstraction, dependency injection, and deterministic memory usage.

Key Features

• Platform independent: Uses a pure-virtual Hardware Abstraction Layer (HAL) for I2C communication so the driver can run on anything from bare-metal MCUs to Linux userspace.
• Production-grade math: Implements Bosch-recommended 64-bit fixed-point compensation formulas for targets without an FPU.
• Zero dynamic allocation: All operations use the stack or pre-allocated objects, suitable for safety-critical and real-time systems.
• Burst reads: Reads sensor data in a single 6-byte burst to ensure register consistency.

Architecture

The project follows the Dependency Inversion Principle: the BME280 driver depends on the II2CBus/ISPIBus interface rather than on concrete hardware implementations.

1. include/II2CBus.hpp — The abstract interface defining read/write operations.
2. include/ISPIBus.hpp — The abstract interface defining transfer operation.
3. include/BME280.hpp — Core driver logic, register mapping, and compensation math.
4. src/LinuxI2CBus.hpp & src/LinuxI2CBus.cpp — Linux-specific implementation using /dev/i2c-x.
5. src/LinuxSPIBus.hpp & src/LinuxSPIBus.cpp — Linux-specific implementation using /dev/spidev-x.y.

Sensor Specifications

• Operating range: −40 to +85 °C
• Humidity: 0 to 100% RH
• Pressure: 300 to 1100 hPa
• Interfaces: I2C (up to 3.4 MHz) and SPI (up to 10 MHz)
• Typical current: ~3.6 μA at 1 Hz

SPI Notes

• SPI Modes: The BME280 supports SPI Mode 0 (CPOL=0, CPHA=0) and Mode 3 (CPOL=1, CPHA=1). Configure your host SPI controller accordingly before use.
• Speed limits: The sensor supports SPI clock frequencies up to 10 MHz; choose a safe default (e.g. 1 MHz or 4 MHz) and validate timing on your target.
• Register addressing (SPI): SPI transactions use the 7-bit register address; the MSB (8th bit) is reserved for the R/W flag. In other words, to read register 0xF7 you must send the address byte 0xF7 | 0x80 = 0xF7 (read) or 0x77 for a write command with the R/W bit cleared — check your platform's SPI transfer ordering.
• 3-wire vs 4-wire: This driver assumes 4-wire SPI (separate MISO/MOSI). The BME280 also supports 3-wire SPI by enabling spi3w_en in the config register (0xF5) — enabling 3-wire requires additional host-side wiring and driver changes and is not implemented by this example.

Build Instructions

This project uses modern CMake (target-based). To build:

mkdir -p build
cd build
cmake ..
make

To clean build artifacts:

make clean

Usage Example

I2C Example

#include "BME280.hpp"
#include "LinuxI2CBus.hpp"

int main() {
    try {
        LinuxI2CBus i2c("/dev/i2c-1");
        BME280 sensor(i2c, 0x76);

        if (sensor.begin()) {
            float temperature, pressure, humidity;
            if (sensor.readSensor(temperature, pressure, humidity)) {
                // Use values...
            }
        }
    } catch (const std::exception& e) {
        // Handle open or ioctl error
    }
    return 0;
}

SPI Example

#include "BME280.hpp"
#include "LinuxSPIBus.hpp"

int main() {
    try {
        LinuxSPIBus spi("/dev/spidev0.0");
        BME280 sensor(spi);

        if (sensor.begin()) {
            float temperature, pressure, humidity;
            if (sensor.readSensor(temperature, pressure, humidity)) {
                // Use values...
            }
        }
    } catch (const std::exception& e) {
        // Handle open or ioctl error
    }
    return 0;
}

References

• BME280 Datasheet BST-BME280-DS002