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Accelerometer and Magnetometer
Many Gateworks board families come standard with either an Accelerometer, Magnetometer, or other inertial measurement unit (IMU) options.
Supported Devices
The specific devices used on our boards are described by the following table:
| Family | Board | Device | Location |
|---|---|---|---|
| Venice | GW82xx | LIS2DE12 accelerometer | i2c2@0x19 |
| LIS2MDL magnetometer | i2c2@0x1e (loading option) | ||
| GW71xx | LIS2DE12 accelerometer | i2c2@0x19 | |
| LIS2MDL magnetometer | i2c2@0x1e (loading option) | ||
| GW72xx | LIS2DE12 accelerometer | i2c2@0x19 | |
| LIS2MDL magnetometer | i2c2@0x1e (loading option) | ||
| GW73xx | LIS2DE12 accelerometer | i2c2@0x19 | |
| LIS2MDL magnetometer | i2c2@0x1e (loading option) | ||
| GW74xx | LIS2DE12 accelerometer | i2c2@0x19 | |
| Newport | GW64xx-C+ | LIS2DE12 accelerometer | i2c0@0x19 |
| GW63xx-E+ | LIS2DE12 accelerometer | i2c0@0x19 | |
| GW62xx-B+ | LIS2DE12 accelerometer | i2c0@0x19 | |
| Ventana | GW553x | LSM9DS1 IMU | i2c2@0x1c (mag) i2c2@0x6a (accel/gyro) |
| GW54xx | FXOS8700 accelerometer | i2c3@0x1e | |
| GW53xx | FXOS8700 accelerometer | i2c3@0x1e | |
| GW522x | FXOS8700 accelerometer | i2c3@0x1e | |
| GW520x | FXOS8700 accelerometer | i2c3@0x1e |
Individual device information:
| Device | Datasheet | Notes |
|---|---|---|
| LIS2DE12 | link | 3 axis accelerometer |
| LSM9DS1 | link | 9 axis internal mass unit (IMU) (accel/mag/gyro) |
| FXOS8700 | link | 6 axis accelerometer, defaults to low power standby mode and must be enabled |
See examples below for more information.
Software Support
The API used to access these devices varies depending on the device and sometimes the kernel version.
| Device | Kernel API | Kernel Driver |
|---|---|---|
| LIS2DE12 accelerometer | iio | IIO_ST_ACCEL_I2C_3AXIS |
| LIS2MDL magnetometer | iio | IIO_ST_MAGN_I2C_3AXIS |
| LSM9DS1 imu | iio | IIO_ST_MAGN_I2C_3AXIS (mag) IIO_ST_LSM6DSX_I2C (accel/gyro) |
| FXOS8700 accelerometer | iio | FXOS8700_I2C |
Linux industrial I/O bus
The modern approach to IMU devices is to use the Linux IIO subsystem. IIO aims to fill the gap between the somewhat similar hwmon and input subsystems. While the hwmon API is directed at low sample rate sensors (like fan speed control or temperature measurement) the input API is focused on human interaction input devices (keyboard, mouse, touchscreen). In some cases there is considerable
overlap between these and the iio API.
Userspace applications can interact with an IIO driver via either:
/sys/bus/iio/devices/iio:deviceX/- represents a hardware sensor and groups
together the data channels. Common attributes are name, dev,
sampling_frequency_available, and standard attributes. See sysfs-bus-iio for details.
- Example (GW54xx with FXOS8700)
# cat /sys/bus/iio/devices/iio\:device0/sampling_frequency_available 1.5625 6.25 12.5 50 100 200 400 800 # echo 100 > /sys/bus/iio/devices/iio\:device0/sampling_frequency # for i in `seq 1 10`; do cat /sys/bus/iio/devices/iio\:device0/in_accel_x_raw ; done 70 70 70 70 90 90 90 90 90 90
/dev/iio:deviceX- character device node interface used for buffered data transfer and for event information retrieval
- libiio - library for interfacing with Linux IIO devices (Ubuntu: libiio-utils iiod, OpenWrt: iio-utils iiod):
- Example (GW54xx with FXOS8700)
# iio_info Library version: 0.18 (git tag: v0.18) Compiled with backends: local IIO context created with local backend. Backend version: 0.18 (git tag: v0.18) Backend description string: Linux OpenWrt 4.19.106 #0 SMP Tue Feb 25 22:49:24 2020 armv7l IIO context has 1 attributes: local,kernel: 4.19.106 IIO context has 1 devices: iio:device0: fxos8700 6 channels found: accel_y: (input) 5 channel-specific attributes found: attr 0: raw value: -256 attr 1: sampling_frequency ERROR: Invalid argument (-22) attr 2: sampling_frequency_available value: 1.5625 6.25 12.5 50 100 200 400 800 attr 3: scale value: 0.000244 attr 4: scale_available value: 0.000244 0.000488 0.000976 magn_z: (input) 5 channel-specific attributes found: attr 0: raw value: 0 attr 1: sampling_frequency ERROR: Invalid argument (-22) attr 2: sampling_frequency_available value: 1.5625 6.25 12.5 50 100 200 400 800 attr 3: scale value: 0.000244 attr 4: scale_available value: 0.000001200 accel_z: (input) 5 channel-specific attributes found: attr 0: raw value: 0 attr 1: sampling_frequency ERROR: Invalid argument (-22) attr 2: sampling_frequency_available value: 1.5625 6.25 12.5 50 100 200 400 800 attr 3: scale value: 0.000244 attr 4: scale_available value: 0.000244 0.000488 0.000976 magn_x: (input) 5 channel-specific attributes found: attr 0: raw value: -1660 attr 1: sampling_frequency ERROR: Invalid argument (-22) attr 2: sampling_frequency_available value: 1.5625 6.25 12.5 50 100 200 400 800 attr 3: scale value: 0.000244 attr 4: scale_available value: 0.000001200 accel_x: (input) 5 channel-specific attributes found: attr 0: raw value: 82 attr 1: sampling_frequency ERROR: Invalid argument (-22) attr 2: sampling_frequency_available value: 1.5625 6.25 12.5 50 100 200 400 800 attr 3: scale value: 0.000244 attr 4: scale_available value: 0.000244 0.000488 0.000976 magn_y: (input) 5 channel-specific attributes found: attr 0: raw value: 12800 attr 1: sampling_frequency ERROR: Invalid argument (-22) attr 2: sampling_frequency_available value: 1.5625 6.25 12.5 50 100 200 400 800 attr 3: scale value: 0.000244 attr 4: scale_available value: 0.000001200 1 device-specific attributes found: attr 0: current_timestamp_clock value: realtime
- Example (GW54xx with FXOS8700)
References:
Android support via the Android sensor HAL
The Android BSP will register an accelerometer and a magnetometer sensor with the OS and therefore can be used with apps conforming the the Android sensor API.
References:
