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CPP_coding_guidelines.md

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C++ LibMcuLL Coding guidelines

Introduction

This document contains the naming conventions and programming idioms used by C++ LibMcuLL. Some architecture things might be defined here but they will be split off in their own design documents.

Initialization

We prefer brace initialization as much as possible.

Naming things

We follow the google standard naming convention

Peripheral hardware

Peripheral hardware is defined in their own header files related to a specific microcontroller. First the proper namespaces are defined for the peripheral:

namespace libmcuhw::device {

Then a structure definition is made where each of the fields map to a hardware register:

struct Device {
  volatile std::uint32_t CTRL; /*!< Control register */
  volatile std::uint32_t STAT; /*!< Status register */
  volatile std::uint32_t DAT;  /*!< Data register */
  union {
    union {                     /*!< Some composite register structure */
      volatile std::uint32_t U; /*!<  Unified register */
      struct {
        volatile std::uint16_t L; /*!<  VALUE[i].L  Access to L value */
        volatile std::uint16_t H; /*!<  VALUE[i].H  Access to H value */
      };
    } VALUE[sizeIndicator];

    const union {
      volatile std::uint32_t U; /*!<  Unified register */
      struct {
        volatile std::uint16_t L; /*!<  SHADOW[i].L  Access to L value */
        volatile std::uint16_t H; /*!<  SHADOW[i].H  Access to H value */
      };
    } SHADOW[sizeIndicator];
  };
};

Next up are the register namespaces, each namespace holds all the settings to one register and if needed some formatting functions. We use the standard k prefix for constants but we do deviate from the capitalisation to match the microcontroller datasheet.

namespace CTRL {
constexpr inline std::uint32_t kRESERVED_MASK{0x00000FFF}; /*!< register mask for allowed bits */
constexpr inline std::uint32_t kBIT_A{1u << 0};            /*!< Bit A */
constexpr inline std::uint32_t kBIT_B{1u << 1};            /*!< Bit B */
constexpr inline std::uint32_t kBIT_C{1 << 2};             /*!< Bit C */
constexpr inline std::uint32_t kFIELD_A_MASK{0xF << 3};    /*!< Bit field A */
/**
 * @brief Format A field
 * @param Some value
 * @return formatted data for FIELD_A
 */
constexpr inline std::uint32_t FIELD_A(std::uint32_t prescale) {
  return prescale << 3;
}
constexpr inline std::uint32_t kFIELD_B_MASK{0xF << 7};   /*!< Bit field B */
/**
 * @brief Format B field
 *
 * @param Some value
 * @return formatted data for FIELD_B
 */
constexpr inline std::uint32_t FIELD_B(std::uint32_t prescale) {
  return prescale << 7;
}
} //namespace CTRL
namespace STAT {
constexpr inline std::uint32_t RESERVED_MASK{0x00000FFF}; /*!< register mask for allowed bits */
constexpr inline std::uint32_t STATUS_A_MASK{1u << 0};    /*!< status A mask */
constexpr inline std::uint32_t STATUS_B_MASK{1u << 1};    /*!< status B mask */
} // namespace STAT

Peripheral software