SMI230 Input Sensor-API and Sensor Driver

Table of Contents

• Introduction
• License
• Sensor interfaces
• Architecture
• Continuous Integration
• Operation examples

Introduction

SMI230 is a system-in-package inertial measurement unit which offers accurate acceleration and angular rate measurements. Due to system-in-package approach of SMI230 (two sensors in single package), the gyroscope and acceleration data is acquired in a non-synchronized manner. However, synchronization between accelerometer and gyroscope can be achieved: The software modules in this repository are provided as reference for SMI230 users and shall demonstrate exemplarily the usage of the following features:

• Data synchronization.
• Data collection from FIFO.

Note: SMI230 is rather an Industrial I/O (IIO) than an input device. Therefore, we now implement SMI230 as an IIO driver (see GitHub). Further development will only happen on the IIO driver, not on the input driver anymore.

Note: The sensor driver utilizes a sensor API, which is following BMI08x's sensor API, available on GitHub.

Note: The data synchronization feature utilizes the sensor's configuration, which is following BMI08x sensor configuration, available on GitHub.

License

See LICENSE file

Sensor interfaces

• I2C
• SPI

Architecture

                  User space
-------------------------------------------------------
                 |          |
               sysfs       dev
                 \          /
               input-subsystem
                      |
sensor_API <-- smi230_driver --> smi230_SPI/I2C_driver
                                           |
                                      SPI/I2C_bus
                                           |
-------------------------------------------------------
                  Hardware

Operation examples

1. Userspace The driver exposes a device file node under /dev/input/event*, which can be read as a normal Linux file. Tools like evtest can also be used for read data out. E.g.:

sudo evtest /dev/input/event0

The data will be displayed on the console with timestamp.

2. Sysfs The driver also exposes a set of sysfs nodes under /sys/devices/virtual/input/input*, where users can get information about the sensor and also control the sensor. E.g.:

# read the acc power config
cat /sys/devices/virtual/input/SMI230ACC/pwr_cfg

# set the acc power config active, this command is needed if acc needs to be fully fuctional.
echo 0 > /sys/devices/virtual/input/SMI230ACC/pwr_cfg

# set the acc power config suspend
echo 3 > /sys/devices/virtual/input/SMI230ACC/pwr_cfg

# read the gyro power config
cat /sys/devices/virtual/input/SMI230GYRO/pwr_cfg

# set the gyro power config active, this command is needed if gyro needs to be fully fuctional.
echo 0 > /sys/devices/virtual/input/SMI230GYRO/pwr_cfg

# set the gyro power config suspend
echo 3 > /sys/devices/virtual/input/SMI230GYRO/pwr_cfg

# read the chip id
cat /sys/devices/virtual/input/SMI230GYRO/chip_id

# read the synced acc data
cat /sys/devices/virtual/input/SMI230ACC/data_sync

# read the asynced acc data
cat /sys/devices/virtual/input/SMI230ACC/acc_value

# read the gyro data
cat /sys/devices/virtual/input/SMI230GYRO/gyro_value