8.0 KiB
Index
* Introduction
* Driver Integration details
* Android SensorHAL integration
* Linux SensorHAL integration
* More information
* Copyright
Introduction
This repository contains asm330lhh IMU STMicroelectronics MEMS sensor linux driver support for kernel version 4.14.
Data collected by asm330lhh STM sensor are pushed to userland through the kernel buffers of Linux IIO framework. User space applications can get sensor events by reading the related IIO devices created in the /dev directory (/dev/iio{x}). Please see IIO for more information.
Asm330lhh IMU STM MEMS sensor support I2C/SPI digital interface. Please refer to I2C and SPI for detailed documentation.
The STM Hardware Abstraction Layer (HAL) defines a standard interface for STM sensors allowing Android to be agnostic about low level driver implementation. The HAL library is packaged into modules (.so) file and loaded by the Android or Linux system at the appropriate time. For more information see AOSP HAL Interface
STM Sensor HAL is leaning on Linux IIO framework to gather data from sensor device drivers and to forward samples to the Android Framework
Driver Integration details
In order to explain how to integrate Asm330lhh IMU STM sensor into the kernel, please consider the following example
Source code integration
- Copy driver source code into your linux kernel target directory (e.g. drivers/iio/imu)
- Edit related Kconfig (e.g. drivers/iio/imu/Kconfig) adding ASM330LHH support:
source "drivers/iio/imu/st_asm330lhh/Kconfig"
- Edit related Makefile (e.g. drivers/iio/imu/Makefile) adding the following line:
obj-y += st_asm330lhh/
Device Tree configuration
To enable driver probing, add the asm330lhh node to the platform device tree as described below.
Required properties:
- compatible: "st,asm330lhh"
- reg: the I2C address or SPI chip select the device will respond to
- interrupt-parent: phandle to the parent interrupt controller as documented in interrupts
- interrupts: interrupt mapping for IRQ as documented in interrupts
Recommended properties for SPI bus usage:
- spi-max-frequency: maximum SPI bus frequency as documented in SPI
Optional properties:
- st,drdy-int-pin: MEMS sensor interrupt line to use (default 1)
I2C example (based on Raspberry PI 3):
&i2c0 { status = "ok"; #address-cells = <0x1>; #size-cells = <0x0>; asm330lhh@6b { compatible = "st,asm330lhh"; reg = <0x6b>; interrupt-parent = <&gpio>; interrupts = <26 IRQ_TYPE_EDGE_RISING>; };
SPI example (based on Raspberry PI 3):
&spi0 { status = "ok"; #address-cells = <0x1>; #size-cells = <0x0>; asm330lhh@0 { spi-max-frequency = <500000>; compatible = "st,asm330lhh"; reg = <0>; interrupt-parent = <&gpio>; interrupts = <26 IRQ_TYPE_EDGE_RISING>; };
Kernel configuration
Configure kernel with make menuconfig (alternatively use make xconfig or make qconfig)
Device Drivers ---> <M> Industrial I/O support ---> Inertial measurement units ---> <M> STMicroelectronics ASM330LHH sensor --->
Android SensorHAL integration
STM Sensor HAL is written in C++ language using object-oriented design. For each hw sensor there is a custom class file (Accelerometer.cpp, Gyroscope.cpp) which extends the common base class (SensorBase.cpp).
Copy the HAL source code into <AOSP_DIR>/hardware/STMicroelectronics/SensorHAL_IIO folder. During building process Android will include automatically the SensorHAL Android.mk. In <AOSP_DIR>/device/<vendor>/<board>/device.mk add package build information:
PRODUCT_PACKAGES += sensors.{TARGET_BOARD_PLATFORM}
Note: device.mk can not read $(TARGET_BOARD_PLATFORM) variable, read and replace the value from your BoardConfig.mk (e.g. PRODUCT_PACKAGES += sensors.msm8974 for Nexus 5)
To compile the SensorHAL_IIO just build AOSP source code from $TOP folder
$ cd <AOSP_DIR>
$ source build/envsetup.sh
$ lunch <select target platform>
$ make V=99
The compiled library will be placed in <AOSP_DIR>/out/target/product/<board>/system/vendor/lib/hw/sensor.{TARGET_BOARD_PLATFORM}.so
To configure sensor the Sensor HAL IIO use mm utility from HAL root folder
since Android 7
$mm sensors-defconfig (default configuration)
$mm sensors-menuconfig
after Android 7
make -f Makefile_config sensors-defconfig (default configuration)
make -f Makefile_config sensors-menuconfig
Linux SensorHAL integration
Linux Sensor HAL share the same source code of Android Sensor HAL. Before compiling the Linux Sensor HAL IIO you need to follow the same procedure listed in previous chapter "Android SensorHAL integration" To cross compile Linux Sensor HAL must export the following shell variables
export AOSP_DIR=<AOSP_DIR> export ARCH= export CROSS_COMPILE=
then in <AOSP_DIR>/hardware/STMicroelectronics/SensorHAL_IIO folder type
make
it will produce a SensorHAL.so file containing the library. In relative pat Documentation/LinuxHal/ there are some examples explaining how to use Linux Sensor HAL
Copyright
Copyright (C) 2017 STMicroelectronics
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.
More Information
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/iio
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/i2c
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/spi
Copyright Driver
Copyright (C) 2017 STMicroelectronics
This software is distributed under the GNU General Public License - see the accompanying COPYING file for more details.
Copyright SensorHAL
Copyright (C) 2017 STMicroelectronics
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.