/*!
* \file utl/com/i2c_bb.h
* \brief A bit banking implementation of i2c bus inherited from
* i2c_i base class.
*
* 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 .
*
*/
#ifndef __utl_com_i2c_bb_h__
#define __utl_com_i2c_bb_h__
#include
#include
#include
namespace utl {
/*!
* \ingroup Communication
* \brief A bit banking implementation of i2c bus
* inherited from \ref i2c_i base class.
* \sa i2c_i
*/
//!@{
/*!
* \brief
* I2C bit banking interface template class providing
* an I2C using bit banking using CRTP.
* \param impl_t The CRTP type (the derived/implementation class typename).
*/
template
class i2c_bb_i : public i2c_i> {
_CRTP_IMPL(impl_t);
friend i2c_i>;
public:
using type = i2c_bb_i; //!< Export type as identity meta-function
using Sequence = typename i2c_i::Sequence;
//! SDA pin direction enumerator
enum class SDAMode {
INPUT =0,
OUTPUT
};
/*!
* \name Object lifetime
*/
//!@{
protected:
//! \brief A default destructor, allow destructor from derived only
~i2c_bb_i () noexcept = default;
//! \brief A default constructor
i2c_bb_i (uint32_t clk) noexcept
: usec_ {1000000/(2*clk)} { }
//!@}
/*!
* \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
*/
//!@{
private:
/*!
* Implementers's sda pin function
* \param st In SDA_OUTPUT mode, selects the pin output state
* \return In SDA_INPUT mode return the pin input state
*/
bool SDA (SDAMode mode, bool st) { return impl().SDA (mode, st); }
void SCL (uint8_t st) { impl().SCL (st); } //!< Implementers's scl pin function
void delay (uint32_t usec) { impl().delay(usec); } //!< Implementers's usec delay function
//!@}
/*!
* \name Implementation of base requirements
*/
//!@{
private:
uint32_t _clock () const { return 1000000/(2*usec_); }
void _clock (uint32_t c) { usec_ = 1000000/(2*c); }
void _start (); //!< Send start functionality
void _stop (); //!< Send stop functionality
byte_t _rx_data (bool ack, Sequence seq);
bool _tx_data (byte_t byte, Sequence seq);
uint32_t usec_; //!< half period of I2C bus
//!@}
};
/*
* ============= User functions ================
*/
/*!
* \brief
* Send a START bit to the bus
* \return none
*/
template
void i2c_bb_i::_start (void) {
//Initially set pins
SDA (SDAMode::OUTPUT, 1);
SCL (1);
delay (usec_);
SDA (SDAMode::OUTPUT, 0);
delay (usec_);
SCL (0); //Clear Clock
}
/*!
* \brief
* Send a START bit to the bus
* \return none
*/
template
void i2c_bb_i::_stop (void) {
//Stop bit Operation
SDA (SDAMode::OUTPUT, 0);
SCL (0);
SCL (1);
delay (usec_);
SDA (SDAMode::OUTPUT, 1);
delay (usec_);
}
/*!
* \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.
*/
template
byte_t i2c_bb_i::_rx_data (bool ack, Sequence seq) {
byte_t byte {0};
//Initial conditions
SCL (0);
SDA (SDAMode::INPUT, 0);
if (seq == Sequence::BYTE || seq == Sequence::BYTEnACK) {
// read 8 data bits
for (int i=8 ; i!=0 ; --i) {
byte <<= 1;
SCL (1);
delay (usec_);
byte |= SDA (SDAMode::INPUT, 0);
SCL (0);
delay (usec_);
}
}
if (seq == Sequence::ACK || seq == Sequence::BYTEnACK) {
SDA (SDAMode::OUTPUT, !ack); //Send (or not) ACK bit
SCL (1);
delay (usec_);
SCL (0); // Keep the bus busy
SDA (SDAMode::OUTPUT, 0);
}
return byte;
}
/*!
* \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
*/
template
bool i2c_bb_i::_tx_data (byte_t byte, Sequence seq) {
bool ack {false};
//Initial conditions
SCL (0);
SDA (SDAMode::OUTPUT, 0);
if (seq == Sequence::BYTE || seq == Sequence::BYTEnACK) {
//Send 8 bit data
for (int i=8 ; i!=0 ; --i) {
//Send MSB
SDA (SDAMode::OUTPUT, byte & 0x80);
byte <<= 1;
SCL (1);
delay (usec_);
SCL (0);
delay (usec_);
}
}
if (seq == Sequence::ACK || seq == Sequence::BYTEnACK) {
// Get ACK
SDA (SDAMode::INPUT, 0);
SCL (1);
delay (usec_);
ack = !SDA (SDAMode::INPUT, 0);
SCL (0); // Keep the bus busy
delay (usec_);
SDA (SDAMode::OUTPUT, 0);
}
return ack;
}
/*!
* \brief
* A virtual base class interface specialization.
* Using the private virtual interface we provide the interface from
* i2c_i
* \param impl_t = virtual_tag
*/
template<>
class i2c_bb_i : public i2c_i {
public:
using type = i2c_bb_i; //!< Export type as identity meta-function
using Sequence = typename i2c_i::Sequence;
//! SDA pin direction enumerator
enum class SDAMode {
INPUT =0,
OUTPUT
};
/*!
* \name Object lifetime
*/
//!@{
protected:
//! \brief Constructor
i2c_bb_i (uint32_t clk) noexcept
: usec_ {1000000/(2*clk)} { }
//! \brief Virtual destructor
virtual ~i2c_bb_i () noexcept = default;
//!@}
/*!
* \name Implementation requirements
*/
//!@{
private:
/*!
* Implementers's sda pin function
* \param st In SDA_OUTPUT mode, selects the pin output state
* \return In SDA_INPUT mode return the pin input state
*/
virtual bool SDA (SDAMode mode, bool st) =0;
virtual void SCL (bool st) =0; //!< Implementers's scl pin function
virtual void delay (uint32_t usec) =0; //!< Implementers's usec delay function
//!@}
/*!
* \name Implementation of base requirements
*/
//!@{
private:
uint32_t _clock () const final { return 1000000/(2*usec_); }
void _clock (uint32_t c) final { usec_ = 1000000/(2*c); }
void _start () final;
void _stop () final;
byte_t _rx_data (bool ack, Sequence seq) final;
bool _tx_data (byte_t byte, Sequence seq) final;
//! half period of I2C bus
uint32_t usec_;
//!@}
};
/*!
* \brief
* Send a START bit to the bus
* \return none
*/
void i2c_bb_i::_start (void) {
//Initially set pins
SDA (SDAMode::OUTPUT, 1);
SCL (1);
delay (usec_);
SDA (SDAMode::OUTPUT, 0);
delay (usec_);
SCL (0); //Clear Clock
}
/*!
* \brief
* Send a START bit to the bus
* \return none
*/
void i2c_bb_i::_stop (void) {
//Stop bit Operation
SDA (SDAMode::OUTPUT, 0);
SCL (0);
SCL (1);
delay (usec_);
SDA (SDAMode::OUTPUT, 1);
delay (usec_);
}
/*!
* \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 i2c_bb_i::_rx_data (bool ack, Sequence seq) {
byte_t byte {0};
//Initial conditions
SCL (0);
SDA (SDAMode::INPUT, 0);
if (seq == Sequence::BYTE || seq == Sequence::BYTEnACK) {
// read 8 data bits
for (int i=8 ; i!=0 ; --i) {
byte <<= 1;
SCL (1);
delay (usec_);
byte |= SDA (SDAMode::INPUT, 0);
SCL (0);
delay (usec_);
}
}
if (seq == Sequence::ACK || seq == Sequence::BYTEnACK) {
SDA (SDAMode::OUTPUT, !ack); //Send (or not) ACK bit
SCL (1);
delay (usec_);
SCL (0); // Keep the bus busy
SDA (SDAMode::OUTPUT, 0);
}
return byte;
}
/*!
* \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 i2c_bb_i::_tx_data (byte_t byte, Sequence seq) {
bool ack {false};
//Initial conditions
SCL (0);
SDA (SDAMode::OUTPUT, 0);
if (seq == Sequence::BYTE || seq == Sequence::BYTEnACK) {
//Send 8 bit data
for (int i=8 ; i!=0 ; --i) {
//Send MSB
SDA (SDAMode::OUTPUT, byte & 0x80);
byte <<= 1;
SCL (1);
delay (usec_);
SCL (0);
delay (usec_);
}
}
if (seq == Sequence::ACK || seq == Sequence::BYTEnACK) {
// Get ACK
SDA (SDAMode::INPUT, 0);
SCL (1);
delay (usec_);
ack = !SDA (SDAMode::INPUT, 0);
SCL (0); // Keep the bus busy
delay (usec_);
SDA (SDAMode::OUTPUT, 0);
}
return ack;
}
//!@}
} // namspace utl
#endif // #ifndef __utl_com_i2c_bb_h__