TC74 Temperature Sensor Driver

Overview

The TC74 is a digital embedded temperature sensor. It is capable of reading temperatures from -0°C to +125°C. The TC74 communicates over I2C. This driver provides a simple C++ object oriented driver for interfacing with the TC74, and is agnostic to any embedded platform.

How to Use

Use as Git Submodule

1. Add this project as a git submodule.

   git submodule add https://github.com/LawrenceStanton/TC74 Modules/TC74

2. Build with CMake by adding as a subdirectory.

   # Add to Your Top-Level CMakeLists.txt
   add_subdirectory(Modules/TC74)
   # ...
   target_link_libraries(${YOUR_EXECUTABLE_NAME} PRIVATE 
       TC74
   )    

3. Provide an I2C interface when constructing the driver. Refer to Design Patterns below and TC74.hpp for more information.

4. Construct the derived TC74 I2C interface and class object.

   // Construct the I2C interface
   MyI2C i2cInterface(myParams);
   // Construct the HDC1080 class object
   TC74 sensor(&i2cInterface);

Design Patterns

This driver follows a strategy design pattern with regards to the I2C interface. The driver defines a I2C interface (TC74::I2C). The user must then provide a concrete implementation of this interface, and provide it to the driver class via dependency injection in the constructor.

classDiagram
direction RL
    class TC74 {
        +class I2C*
        ~ I2C &i2c
        +TC74(I2C &i2c)
    }
    class `TC74::I2C` {
        <<Interface>>
        +read(MemoryAddress address)*
        +write(MemoryAddress address, Register data)*
    }
    class MyI2C {
        +MyI2C(DeviceAddress address, MyParams myParams)
        +read(MemoryAddress address)
        +write(MemoryAddress address, Register data)
    }
    MyI2C <|.. `TC74::I2C`
    TC74 -- `TC74::I2C`
    TC74 o-- MyI2C

Loading

Example

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 a set of functions for reading and writing to I2C devices. The user can then implement the TC74::I2C interface by calling the HAL functions.```

#include "TC74.hpp"
#include "stm32f0xx_hal.h"

using std::optional;
using std::nullopt;

class MyI2C : public TC74::I2C {
    I2C_HandleTypeDef &myParams;
    DeviceAddress i2cAddress;
public:
    MyI2C(I2C_HandleTypedef &hi2c, DeviceAddress i2cAddress) : hi2c(hi2c), i2cAddress(i2cAddress) {}

    optional<Register> read(MemoryAddress memoryAddress) noexcept override final {
        static_assert(sizeof(Register) == sizeof(uint8_t));
        uint8_t data;
        auto halStatus = HAL_I2C_Mem_Read(
            &this->hi2c, 
            static_cast<uint8_t>(this->deviceAddress) << 1,
            static_cast<uint8_t>(this->memoryAddress),
            sizeof(uint8_t),&data, sizeof(data), 100    
        );
        if(halStatus != HAL_OK) return nullopt;
        else return data;
    }

    void write(MemoryAddress address, Register data) noexcept override final {
        static_assert(sizeof(Register) == sizeof(uint8_t));
        auto status = HAL_I2C_Mem_Write(
            &this->hi2c, //
            static_cast<uint8_t>(this->deviceAddress) << 1,
            static_cast<uint8_t>(memoryAddress),
            sizeof(uint8_t), &data, sizeof(data), 100
        );
        if (status != HAL_OK) return nullopt;
        else return data;
    }
};

Testing

This driver is unit tested using the GoogleTest and GoogleMock framework. The tests are located in the Test directory. The tests can be built and run using CMake.

Given the limitations of many embedded systems, the tests are intended to be run on a host machine, and not the embedded platform itself. This is done by checking the CMake variable CMAKE_CROSSCOMPILING and only building the tests if this is false. To build the tests, simply configure CMake to perform a local build.

The tests can then be run using CTest.

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

These tests will also be included in the parent build if enable_testing() is called in the top-level CMakeLists.txt file.