utl/include/utl/com/i2c.h

/*!
 * \file    /utl/com/i2c.h
 * \brief   An Abstract base class interface for the i2c bus
 *
 * Copyright (C) 2018 Christos Choutouridis
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation, either version 3
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */
#ifndef _utl_com_i2c_h__
#define _utl_com_i2c_h__

#include <utl/impl/impl.h>
#include <utl/helper/crtp.h>
#include <utl/meta/sfinae.h>

namespace utl {

   /*!
    * \ingroup Communication
    * \brief   Abstract base class for i2c bus
    */
   //!@{

   /*!
    * \brief
    *    this class force a common interface for I2C communication
    *    protocol implementations using CRTP
    * \param   impl_t   The CRTP type (the derived/implementation class typename).
    */
   template <typename impl_t>
   class i2c_i {
      _CRTP_IMPL(impl_t);

   public:
      using type = i2c_i<impl_t>;     //!< Export type as identity meta-function
      //! I2C transmit/receive sequence
      enum class Sequence {
         BYTE =0, //!< Only read/write byte     [8 clocks]
         ACK,     //!< Only send/receive ack    [1 clock]
         BYTEnACK //!< Read/Write byte and ack  [9 clocks]
      };

   /*!
    * \name Object lifetime
    */
   //!@{
   protected:
      i2c_i () = default;              //!< Allow constructor from derived only
      ~i2c_i () = default;             //!< Allow destructor from derived only
      i2c_i (const type&) = delete;    //!< No copies
      type& operator= (const type&) = delete;
   //!@}

   /*!
    * \name Implementation requirements
    * \note
    *    In order for the implementation to have the following as private members
    *    it also need to declare this class as friend
    */
   //!@{
   //! uint32_t _frequency () const;           < clock frequency of the bus [Hz]
   //! void _frequency (uint32_t);             < set clock frequency of the bus [Hz]
   //! void _start();                          < Send start functionality
   //! void _stop();                           < Send stop functionality
   //! byte_t _read (bool ack, Sequence seq);  < Receive a byte from the i2c bus.
   //! bool _write (byte_t byte, Sequence seq);< Transmit a byte to the i2c bus.
   //!@}

   /*!
    * \name Get/Set functions
    */
   //!@{
   public:
      uint32_t frequency () const { return impl()._frequency (); }   //!< \return clock frequency of the bus
      void frequency (uint32_t f) { impl()._frequency (f); }         //!< \brief set clock frequency of the bus
   //!@}

   /*!
    * \name User functions
    */
   //!@{
   public:
      void start() { impl()._start (); }   //!< Send start functionality
      void stop () { impl()._stop (); }    //!< Send stop functionality

      /*!
       * \brief
       *    Receive a byte from the i2c bus.
       * \param  ack    Optional ack bit.
       *    \arg 1  ACK the reception
       *    \arg 0  Don't ACK the reception.
       * \param   seq   The operation sequence to execute
       *    \arg  Sequence::BYTE       Receive only the byte, do not send ack clock
       *    \arg  Sequence::ACK        Send only the ack bit
       *    \arg  Sequence::BYTEnACK   Receive the byte and send the ack bit
       * \return  The byte received.
       */
      byte_t read (bool ack, Sequence seq =Sequence::BYTEnACK) {
         return impl()._read (ack, seq);
      }

      /*!
       * \brief
       *    Transmit a byte to the i2c bus.
       * \param  byte   The byte to send.
       * \param   seq   The operation sequence to execute
       *    \arg  Sequence::BYTE       Transmit only the byte, do not read ack bit
       *    \arg  Sequence::ACK        Read only the ack bit
       *    \arg  Sequence::BYTEnACK   Transmit the byte and read the ack bit
       * \return Slave's ACK bit
       *    \arg false  Slave didn't ACK
       *    \arg true   Slave did ACK
       */
      bool write (byte_t byte, Sequence seq =Sequence::BYTEnACK) {
         return impl()._write (byte, seq);
      }
   //!@}

   };

   /*!
    * \brief
    *    A virtual base class specialization
    * \param   impl_t   = virtual_tag
    */
   template<>
   class i2c_i <virtual_tag> {
   public:
      using type = i2c_i <virtual_tag>;   //!< Export type as identity meta-function

      //! I2C transmit/receive sequence
      enum class Sequence {
         BYTE=0,  //!< Only read/write byte     [8 clocks]
         ACK,     //!< Only send/receive ack    [1 clock]
         BYTEnACK //!< Read/Write byte and ack  [9 clocks]
      };

   /*!
    * \name Object lifetime
    */
   //!@{
   protected:
      i2c_i () = default;                 //!< Allow constructor from derived only
      i2c_i (const type&) = delete;       //!< No copies
      type& operator= (const type&) = delete;
   public:
      virtual ~i2c_i () = default;        //!< Virtual default destructor
   //!@}

   /*!
    * \name Implementation requirements
    */
   //!@{
   private:
      virtual uint32_t _frequency () const = 0;   //!< \return clock frequency of the bus [Hz]
      virtual void _frequency (uint32_t) = 0;     //!< \brief set clock frequency of the bus [Hz]
      virtual void _start() = 0;                  //!< Send start functionality
      virtual void _stop() = 0;                   //!< Send stop functionality
      virtual byte_t _read (bool ack, Sequence seq) = 0;   //!< Receive a byte from the i2c bus.
      virtual bool _write (byte_t byte, Sequence seq) = 0; //!< Transmit a byte to the i2c bus.
   //!@}
   /*!
    * \name Get/Set functions
    */
   //!@{
   public:
      uint32_t frequency () const { return _frequency(); } //!< \return clock frequency of the bus [Hz]
      void frequency (uint32_t f) { _frequency(f); }       //!< \brief set clock frequency of the bus [Hz]
   //!@}

   /*!
    * \name User functions
    */
   //!@{
   public:
      void start () { _start(); }
      void stop () { _stop(); }
      /*!
       * \brief
       *    Receive a byte from the i2c bus.
       * \param  ack    Optional ack bit.
       *    \arg 1  ACK the reception
       *    \arg 0  Don't ACK the reception.
       * \param   seq   The operation sequence to execute
       *    \arg  Sequence::BYTE       Receive only the byte, do not send ack clock
       *    \arg  Sequence::ACK        Send only the ack bit
       *    \arg  Sequence::BYTEnACK   Receive the byte and send the ack bit
       * \return   The byte received.
       */
      byte_t read (bool ack, Sequence seq =Sequence::BYTEnACK) {
         return _read (ack, seq);
      }
      /*!
       * \brief
       *    Transmit a byte to the i2c bus.
       * \param  byte   The byte to send.
       * \param   seq   The operation sequence to execute
       *    \arg  Sequence::BYTE       Transmit only the byte, do not read ack bit
       *    \arg  Sequence::ACK        Read only the ack bit
       *    \arg  Sequence::BYTEnACK   Transmit the byte and read the ack bit
       * \return Slave's ACK bit
       *    \arg false  Slave didn't ACK
       *    \arg true   Slave did ACK
       */
      bool write (byte_t byte, Sequence seq =Sequence::BYTEnACK) {
         return _write (byte, seq);
      }
   //!@}

   };

#if defined _utl_have_concepts
   /*!
    * i2c interface concept
    */
   template <typename T>
   concept bool i2c_c = requires (T t, const T ct, typename T::Sequence s) {
      // Object type
      requires not_<std::is_copy_constructible<T>::value>::value;
      requires not_<std::is_copy_assignable<T>::value>::value;
      // Methods
      {ct.frequency()} -> uint32_t;
      {t.frequency(0)} -> void;
      {t.start()}      -> void;
      {t.stop()}       -> void;
      {t.read (1, s)}  -> byte_t;
      {t.write(0, s)}  -> bool;
   };
#else
   namespace i2c_i_cnpt {
      using std::declval;

      template <class _Tp> using try_cfreq_t = decltype (declval<const _Tp>().frequency());
      template <class _Tp> using try_freq_t  = decltype (declval<_Tp>().frequency(declval<uint32_t>()));
      template <class _Tp> using try_start_t = decltype (declval<_Tp>().start());
      template <class _Tp> using try_stop_t  = decltype (declval<_Tp>().stop());
      template <class _Tp> using try_read_t
            = decltype (declval<_Tp>().read (declval<bool>(), declval<typename _Tp::Sequence>()));
      template <class _Tp> using try_write_t
            = decltype (declval<_Tp>().write (declval<byte_t>(), declval<typename _Tp::Sequence>()));

      //! Primary template to catch any non I2C interface types
      template <typename _Tp, typename =void>
      struct is_i2c_ : false_ { };

      //! template to catch a proper I2C interface type
      template <typename _Tp>
      struct is_i2c_ <_Tp,
         void_t <
            typename _Tp::Sequence,
            use_if_same_t <uint32_t,try_cfreq_t <_Tp>>,
            use_if_same_t <void,    try_freq_t <_Tp>>,
            use_if_same_t <void,    try_start_t <_Tp>>,
            use_if_same_t <void,    try_stop_t <_Tp>>,
            use_if_same_t <byte_t,  try_read_t <_Tp>>,
            use_if_same_t <bool,    try_write_t <_Tp>>
         >  //!^ SFINAE may apply inside if_same_t<> also
      > : true_ { };
   }
   /*!
    * Value meta-programming function alias for I2C interface checking
    * \param   _Tp  Type to check
    * \return  True if _Tp is a i2c interface
    */
   template <typename _Tp>
   constexpr bool i2c_c = i2c_i_cnpt::is_i2c_<_Tp>::value;
#endif

   //!@}

} // namespace utl

#endif // _utl_com_i2c_h__