TMP116 Digital Temperature Sensor

Overview

The TMP116 is an embedded temperature sensor, produced by Texas Instruments, and operates over a SMBus digital communications interface. This driver provides a simple C++ object-orientated driver to allow for control and data reception from this device, and is agnostic to any embedded platform.

The design philosophy of this driver is comparatively unique in the embedded systems space. The object orientated approach results in a simple, scalable, and extensible driver, which is easy to use and understand. The driver is also designed to be agnostic to any embedded platform, and is therefore portable to any embedded system, with any I2C implementation (see Design Patterns). The system also adopts strong unit testing with the Google Test framework, allowing for a high degree of confidence in the driver's operation and ease of further development. CMake also allows for easy integration into parent projects.

How to Use

1. Add this project as a git submodule.

   git submodule add https://github.com/LawrenceStanton/TMP116 Modules/TMP116

2. Build with CMake by adding as a subdirectory.

   # Add to Your Top-Level CMakeLists.txt
   add_subdirectory(Modules/TMP116)
   # ...
   target_link_libraries(${YOUR_EXECUTABLE_NAME} PRIVATE 
       TMP116::TMP116
   )    

   If you are not using CMake, you must then simply add the HDC1080 include directory and source files to your chosen build system.

3. Provide an I2C interface when constructing the driver. Refer to Design Patterns below and TMP116.hpp for more information.

4. Construct the TMP116 I2C interface and class object.

   // Construct the I2C interface
   MyI2C i2cInterface(myParams);
   // Construct the HDC1080 class object
   TMP116::TMP116 sensor(&i2cInterface);

Design Patterns

This driver follows an Strategy Design Pattern with regards to the I2C communication. The driver defines an I2C interface (TMP116::I2C). The user must then provide a concrete implementation of this interface, and provide it to the driver class.

Often a concrete implementation will simply translate the I2C operations to the embedded platform's Hardware Abstraction Layer (HAL). For example, the STM32Cube HAL provides an I2C interface, which can be used to implement the I2C operations. However, the user may also provide their own low level implementation, which may be useful in some applications, or mocked implementation, which may be useful for testing purposes (see Testing).

Example

Below is an example of a typical declaration of the I2C interface.

#include "TMP116.hpp"

class MyI2C : public TMP116::I2C {
public:
    MyI2C(MyI2CParams params) : params(params) {}
    virtual ~MyI2C() {}

    virtual std::optional<HDC1080::I2C::Register> read(HDC1080::I2C::MemoryAddress address) override;
    virtual std::optional<HDC1080::I2C::Register> write(HDC1080::I2C::MemoryAddress address, HDC1080::I2C::Register) override;
}

// Definitions made in a separate source file.

Refer to [Examples] for concrete examples of this design pattern.

Testing

This driver is unit tested using the GoogleTest and GoogleMock frameworks. The tests are located in the Tests directory.

The tests are built using CMake. Given the limitations of many embedded systems, the tests are designed to be run on a host machine, and not on the embedded system itself. This is done by checking the CMake variable CMAKE_CROSSCOMPILING and only building the tests if this is false. To build the tests, configure your build presets to perform a local build.

If gtest and gmock are not installed on your system, CMake will attempt to automatically download and build them automatically with FetchContent. Disable this behaviour by setting the CMake option TMP116_AUTOFETCH_GTEST to OFF.

Command Line:

cmake -DTMP116_AUTOFETCH_GTEST=OFF

Parent CMakeLists.txt:

set(TMP116_AUTOFETCH_GTEST OFF)
# ...
add_subdirectory(Modules/TMP116)

The tests can then be run using CTest.

mkdir Build && cd Build
cmake ..
cmake --build .
ctest

Run tests automatically be setting test as a build target in your presets.

These tests will be included in the parent build if ctest is also used there.