1 - Introduction

This repository contains examples of low-level platform-independent drivers for STMicroelectronics sensors. Sensor drivers and examples are written in C programming language.

If you are using STM32Cube packages, evaluate also the hardware abstractions STM32Cube-compatible drivers.

The STMicroelectronics naming convention for driver repositories is:

• PARTNUMBER (i.e. hts221) for low-level platform-independent drivers
• stm32-PARTNUMBER (i.e. stm32-hts221) for hardware-abstracted STM32Cube-compatible drivers

1.a - Repository structure

This repository contains two types of folders, identifiable using the following naming convention:

• folder that contains the sensor drivers, named xxxxxxx_STdC where xxxxxxx identifies the sensor part number
• folder that contains the demo project, named _prj_XXXXXXX where XXXXXXX is the name of the ST evaluation board

Another folder, named _resources, cannot be identified with the two types described above and contains other useful resources such as libraries and predefined device configurations used in some examples. In order to clone the complete content of this folder, use the command:

git clone --recursive https://github.com/STMicroelectronics/STMems_Standard_C_drivers

1.b - Sensor driver folder structure

Every sensor driver folder contains:

• xxxxxxx_STdC\driver : this folder points to another repository which contains only the sensor driver files (.h and .c) to be included, or linked directly as a git submodule, in your project. Driver documentation can be generated using the Doxygen tool.
• xxxxxxx_STdC\example: examples showing how to integrate the C driver in a project. They are written for STM32 Microcontrollers using the STM32CubeMX tool, but they can be used as a guideline for every platform.
• README: additional info about the specific driver.

1.c - Demo project folder structure

Every demo project folder contains a single configuration file for the STM32CubeMX tool named _prj_XXXXXXX\XXXXXX.ioc where XXXXXXX is the name of the ST evaluation board.

Using the STM32CubeMX tool (configured with the related MCU package) and the .ioc file, it is possible to create a project in which you can easily run the examples available in each sensor driver folder.

2 - Integration details

The driver is platform-independent, you only need to define the two functions for read and write transactions from the sensor hardware bus (ie. SPI or I²C). A few devices integrate an extra bit in the communication protocol in order to enable multi read/write access, this bit must be managed in read and write functions defined by the user. Please refer to the read and write implementation in the reference examples.

2.a Source code integration

• Include in your project the driver files of the sensor (.h and .c) located in the xxxxxxx_STdC\driver folder of the corresponding product.

• Define in your code the read and write functions that use the I²C or SPI platform driver like the following:

/** Please note that it is MANDATORY: return 0 -> no Error.**/
int32_t platform_write(void *handle, uint8_t Reg, const uint8_t *Bufp, uint16_t len)
int32_t platform_read(void *handle, uint8_t Reg, uint8_t *Bufp, uint16_t len)

• Declare and initialize the structure of the device interface:

xxxxxxx_ctx_t dev_ctx; /** xxxxxxx is the used part number **/
dev_ctx.write_reg = platform_write;
dev_ctx.read_reg = platform_read;

• If needed by the platform read and write functions, initialize the handle parameter:

dev_ctx.handle = &platform_handle;

2.b Required properties

• A standard C language compiler for the target MCU
• A C library for the target MCU and the desired interface (ie. SPI, I²C)

3 - Running examples

Examples are written for STM32 Microcontrollers using the STM32CubeMX tool, but they can be used as a guideline for every platform.

3.a Using STMicroelectronics evaluation boards

When using the supported STMicroelectronics evaluation boards, the example file(.c) can be run without applying any modifications (as is).

In order to run that file, please follow these steps:

1. Download and install the STM32CubeMX tool and the related MCU package (i.e. STM32CubeF4 for NucleoF411 and STEVAL_MKI109V3).
2. Open the .ioc configuration file associated to the selected evaluation board with the STM32CubeMX tool. The .ioc configuration files for the supported evaluation boards can be found in the related ST evaluation board demo project folder.
3. Generate the project using the STM32CubeMX tool and select your preferred IDE / toolchain.
4. Add to your project the STMicroelectronics sensor driver. Driver files are located in the sensor drivers folder atxxxxxxx_STdC\driver\xxxxxxx_reg.c(.h) where xxxxxxx identifies the sensor part number.
5. Add to your project the example source file (.c) that you are interested in. Example files are located in the sensor drivers folder at xxxxxxx_STdC\example where xxxxxxx identifies the sensor part number.
6. Uncomment the selected board definition in section /* STMicroelectronics evaluation boards definition */ in the selected example file (.c).
7. Add the call to the example function inside the while(1) loop in the main() function of the main.c file automatically generated by the STM32CubeMX tool.
8. Enjoy :-)

If you are using STM32Cube packages, evaluate also the hardware-abstracted STM32Cube-compatible drivers specifically designed to be compatible with the STM32Cube. The complete list is provided here.

3.b Running examples using different hardware

If a different MCU is used, please follow these steps:

1. Add the STMicroelectronics sensor driver to your project. Driver files are located in the sensor drivers folder atxxxxxxx_STdC\driver\xxxxxxx_reg.c(.h) where xxxxxxx identifies a sensor part number.

2. Add the example source file (.c) that interests you to your project. Example files are located in the sensor drivers folder at xxxxxxx_STdC\example where xxxxxxx identifies the sensor part number.

3. Comment all the definitions of the boards in section `/* STMicroelectronics evaluation boards definition */ in the selected example file(.c).

4. Add the call to the example function inside the while(1) loop in yourmain() function.

5. Modify in the selected example file (.c) the hardware-related functions:

   • platform_write(void *handle, uint8_t Reg, const uint8_t *Bufp,uint16_t len)
   • platform_read(void *handle, uint8_t Reg, uint8_t *Bufp, uint16_t len)
   • if needed, add/replace the hardware-related functions reported in the example file.

6. Enjoy :-)

More information: http://www.st.com

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