Bosch BSEC Sensor Fusion Library for Apache Mynewt

Introduction

This repo packages the Bosch BSEC Sensor Fusion Library for the BME680 Environmental Sensor into an Apache Mynewt-compatible package.

Quick-Start

1. In a new or existing Mynewt project, add mynewt-bosch-bsec to the list of repos. The repo name is mynewt-bosch-bsec. Use the following for the repo details:

repository.mynewt-bosch-bsec:
    type: github
    vers: 1-latest
    user: amrbekhit
    repo: mynewt-bosch-bsec

2. Run newt upgrade to download and install the repo.
3. Download the Bosch BSEC Sensor Fusion Library. After extracting the archive, identify the correct binary for your device and toolchain under algo/bin/Normal_version. Copy the libalgobsec.a file into the repos/mynewtbosch_bsec/src folder.
4. Make sure to include the BME680 package in your app. This can be found in @apache-mynewt-core/hw/drivers/sensors/bme680.
5. Configure the mynewt-bosch-bsec library. The most important syscfg values are BOSCH_BSEC_TIMER_INIT and BOSCH_BSEC_CONFIG. It is possible to reuse an existing timer rather then set up a new one - if so, simply set BOSCH_BSEC_TIMER_INIT to 0.
6. Persistence of the library state is configured using BOSCH_BSEC_SAVE_STATE. This uses the Mynewt fs library to save a file containing the state.
7. In order to access the data from the sensor, create a callback of type output_ready_fct, and register it with the BSEC library by calling the bosch_bsec_output_cb function. When new data is ready, the callback function will be called with all the new data values.

How It Works

The mynewt-bosch-bsec library creates a thread, called bsec, which initialises the BSEC library and then starts the BSEC loop. This loop regularly polls the BME680 sensor and processes all of the sensor inputs, calling the output_cb function with the new data. If enabled, the library will periodically save the library state to disk. This state is loaded back into the library on bootup.

Lower Power Recommendations

The following is based on using the nRF series of micros with the BME680

• In between polling the sensor, the bsec thread sleeps and thus allows the OS to run the idle task, putting the CPU to sleep and consuming minimal power.
• The main source of power consumption is the timer. It is recommended to use the RTC timer (and adjust BOSCH_BSEC_TIMER_FREQ accordingly), as this can run while the CPU is in sleep mode and consume very little power.