Implement a bit-banged I2C master. More...

#include <BitBangI2C.hxx>

Inheritance diagram for BitBangI2C< HW >:

Public Member Functions
	BitBangI2C (const char *name)
	Constructor.

	~BitBangI2C ()
	Destructor.

void	tick_interrupt ()
	Called at a periodic tick, when enabled.

Public Member Functions inherited from Device
	Device (const char *name)
	Constructor.

virtual	~Device ()
	Destructor.

Private Member Functions
bool	state_start ()
	Execute state machine for sending start condition.

bool	state_stop ()
	Execute state machine for sending the stop condition.

bool	state_tx (uint8_t data)
	Execute data TX state machine.

bool	state_rx (uint8_t *data, bool nack)
	Execute data RX state machine.

bool	state_recovery ()
	Execute recovery state machine.

void	enable () override
	function to enable device

void	disable () override
	function to disable device

int	transfer (struct i2c_msg *msg, bool stop) override
	Method to transmit/receive the data.

Private Member Functions inherited from Atomic
void	lock ()

void	unlock ()

Private Attributes
struct i2c_msg *	msg_
	I2C message to presently act upon

OSSem	sem_
	semaphore to wakeup task level from ISR

int	count_
	the count of data bytes transferred, error if < 0

State	state_
	state machine state

union {

StateStart stateStart_
	I2C start state machine state. More...

StateStop stateStop_
	I2C stop state machine state. More...

StateTx stateTx_
	I2C data TX state machine state. More...

StateRx stateRx_
	I2C data RX state machine state. More...

StateRecovery stateRecovery_
	I2C recovery state machine state. More...

};

bool	stop_
	if true, issue stop condition at the end of the message

bool	clockStretchActive_
	true if the slave is clock stretching.

Additional Inherited Members
Static Public Member Functions inherited from Device
static int	open (struct _reent reent, const char path, int flags, int mode)
	Open a file or device.

static int	close (struct _reent *reent, int fd)
	Close a file or device.

static int	stat (struct _reent reent, const char path, struct stat *stat)
	Get the status information of a file or device.

static int	select (int nfds, fd_set readfds, fd_set writefds, fd_set *exceptfds, long long timeout)
	POSIX select().

static void	select_clear ()
	Clears the current thread's select bits.

Static Public Member Functions inherited from FileIO
static ssize_t	read (struct _reent reent, int fd, void buf, size_t count)
	Read from a file or device.

static ssize_t	write (struct _reent reent, int fd, const void buf, size_t count)
	Write to a file or device.

static _off_t	lseek (struct _reent *reent, int fd, _off_t offset, int whence)
	Change the offset index of a file or device.

static int	fstat (struct _reent reent, int fd, struct stat stat)
	Get the status information of a file or device.

static int	ioctl (int fd, unsigned long int key, unsigned long data)
	Request and ioctl transaction.

static int	fcntl (int fd, int cmd, unsigned long data)
	Manipulate a file descriptor.

static bool	is_device (int fd)
	Test if the file descriptor belongs to a device.

Protected Types inherited from BitBangI2CStates
enum class	State : uint8_t { START , ADDRESS , DATA_TX , DATA_RX , RECOVERY , STOP }
	High level I2C States. More...

enum class	StateStart : uint8_t { SDA_SET , SCL_SET , SDA_CLR , FIRST = SDA_SET , LAST = SDA_CLR }
	Low level I2C start states. More...

enum class	StateStop : uint8_t { SDA_CLR , SCL_SET , SDA_SET , FIRST = SDA_CLR , LAST = SDA_SET }
	Low level I2C stop states. More...

enum class	StateTx : uint8_t { DATA_7_SCL_CLR , DATA_7_SCL_SET , DATA_6_SCL_CLR , DATA_6_SCL_SET , DATA_5_SCL_CLR , DATA_5_SCL_SET , DATA_4_SCL_CLR , DATA_4_SCL_SET , DATA_3_SCL_CLR , DATA_3_SCL_SET , DATA_2_SCL_CLR , DATA_2_SCL_SET , DATA_1_SCL_CLR , DATA_1_SCL_SET , DATA_0_SCL_CLR , DATA_0_SCL_SET , ACK_SDA_SET_SCL_CLR , ACK_SCL_SET , ACK_SCL_CLR , FIRST = DATA_7_SCL_CLR , LAST = ACK_SCL_CLR }
	Low level I2C data TX states. More...

enum class	StateRx : uint8_t { DATA_7_SCL_SET , DATA_7_SCL_CLR , DATA_6_SCL_SET , DATA_6_SCL_CLR , DATA_5_SCL_SET , DATA_5_SCL_CLR , DATA_4_SCL_SET , DATA_4_SCL_CLR , DATA_3_SCL_SET , DATA_3_SCL_CLR , DATA_2_SCL_SET , DATA_2_SCL_CLR , DATA_1_SCL_SET , DATA_1_SCL_CLR , DATA_0_SCL_SET , DATA_0_SCL_CLR , ACK_SDA_SCL_SET , ACK_SCL_CLR , FIRST = DATA_7_SCL_SET , LAST = ACK_SCL_CLR }
	Low level I2C data RX states. More...

enum class	StateRecovery : uint8_t { SDA_SET , DATA_7_SCL_SET , DATA_7_SCL_CLR , DATA_6_SCL_SET , DATA_6_SCL_CLR , DATA_5_SCL_SET , DATA_5_SCL_CLR , DATA_4_SCL_SET , DATA_4_SCL_CLR , DATA_3_SCL_SET , DATA_3_SCL_CLR , DATA_2_SCL_SET , DATA_2_SCL_CLR , DATA_1_SCL_SET , DATA_1_SCL_CLR , DATA_0_SCL_SET , DATA_0_SCL_CLR , ACK_SCL_SET , ACK_SCL_CLR , FIRST = SDA_SET , LAST = ACK_SCL_CLR }
	Low level I2C data RX states. More...

Protected Member Functions inherited from BitBangI2CStates
	BitBangI2CStates ()
	Default constructor.

Protected Member Functions inherited from I2C
	I2C (const char *name)
	Constructor.

	~I2C ()
	Destructor.

Protected Member Functions inherited from Node
	Node (const char *name)
	Constructor.

virtual	~Node ()
	Destructor.

int	open (File , const char , int, int) OVERRIDE
	Open method.

int	close (File *) OVERRIDE
	Close method.

virtual int	fstat (File file, struct stat stat) override
	Get the status information of a file or device.

	Device (const char *name)
	Constructor.

virtual	~Device ()
	Destructor.

Protected Member Functions inherited from FileIO
	FileIO (const char *name)
	Constructor.

virtual	~FileIO ()
	Destructor.

virtual off_t	lseek (File *f, off_t offset, int whence)
	Seek method.

virtual int	fcntl (File *file, int cmd, unsigned long data)
	Manipulate a file descriptor.

virtual bool	select (File *file, int mode)
	Device select method.

Static Protected Member Functions inherited from Device
static void	select_insert (SelectInfo *info)
	Add client to list of clients needing woken.

static void	select_wakeup (SelectInfo *info)
	Wakeup the list of clients needing woken.

static void	select_wakeup_from_isr (SelectInfo info, int woken)
	Wakeup the list of clients needing woken.

static int	open (struct _reent reent, const char path, int flags, int mode)
	Open a file or device.

static int	close (struct _reent *reent, int fd)
	Close a file or device.

static int	stat (struct _reent reent, const char path, struct stat *stat)
	Get the status information of a file or device.

static int	select (int nfds, fd_set readfds, fd_set writefds, fd_set *exceptfds, long long timeout)
	POSIX select().

static void	select_clear ()
	Clears the current thread's select bits.

Static Protected Member Functions inherited from FileIO
static int	fd_alloc (void)
	Allocate a free file descriptor.

static void	fd_free (int fd)
	Free up a file descriptor.

static File *	file_lookup (int fd)
	Looks up a reference to a File corresponding to a given file descriptor.

static int	fd_lookup (File *file)
	Looks up a file descriptor corresponding to a given File reference.

static ssize_t	read (struct _reent reent, int fd, void buf, size_t count)
	Read from a file or device.

static ssize_t	write (struct _reent reent, int fd, const void buf, size_t count)
	Write to a file or device.

static _off_t	lseek (struct _reent *reent, int fd, _off_t offset, int whence)
	Change the offset index of a file or device.

static int	fstat (struct _reent reent, int fd, struct stat stat)
	Get the status information of a file or device.

static int	ioctl (int fd, unsigned long int key, unsigned long data)
	Request and ioctl transaction.

static int	fcntl (int fd, int cmd, unsigned long data)
	Manipulate a file descriptor.

static bool	is_device (int fd)
	Test if the file descriptor belongs to a device.

Protected Attributes inherited from Node
OSMutex	lock_
	protects internal structures.

mode_t	mode_
	File open mode, such as O_NONBLOCK.

unsigned int	references_
	number of open references

Protected Attributes inherited from FileIO
const char *	name
	device name

Static Protected Attributes inherited from FileIO
static const unsigned int	numOpenFiles = 20

static File	files []
	File descriptor pool.

static OSMutex	mutex
	mutual exclusion for fileio

Detailed Description

template<class HW>
class BitBangI2C< HW >

Implement a bit-banged I2C master.

A periodic timer [interrupt] should call the BitBangI2C::tick_interrupt() method at a rate that is one half the desired clock rate. For example, for a 100kHz bus, call once every 5 microseconds. The tick should be enabled to start. The driver will call HW::tick_enable()/HW::tick_disable() to enable/disable the tick as needed to save on spurious interrupts.

Example:

struct I2CHwDefs
{
    class SCL_Pin
    {
    public:
        static void set(bool on)
        {
            ...
        }
        static bool get()
        {
            ...
        }
        static void hw_init()
        {
            ...
        }
    };
 
    class SDA_Pin
    {
    public:
        static void set(bool on)
        {
            ...
        }
        static bool get()
        {
            ...
        }
        static void hw_init()
        {
            ...
        }
    };
 
    static void tick_enable()
    {
        ...
    }
 
    static void tick_disable()
    {
        ...
    }
};
 
BitBangI2C<I2CHwDefs> bitBangI2C("/dev/i2c0", disable_tick, enable_tick);

Template Parameters

HW	hardware interface to the access the SCL and SDA I/O lines

Definition at line 235 of file BitBangI2C.hxx.

Constructor & Destructor Documentation

◆ BitBangI2C()

template<class HW >

BitBangI2C< HW >::BitBangI2C ( const char * name )

inline

Constructor.

Parameters

name	name of this device instance in the file system

Definition at line 242 of file BitBangI2C.hxx.

◆ ~BitBangI2C()

template<class HW >

BitBangI2C< HW >::~BitBangI2C ( )

inline

Destructor.

Definition at line 257 of file BitBangI2C.hxx.

Member Function Documentation

◆ disable()

template<class HW >

void BitBangI2C< HW >::disable ( )

inlineoverrideprivatevirtual

function to disable device

Implements Node.

Definition at line 295 of file BitBangI2C.hxx.

◆ enable()

template<class HW >

void BitBangI2C< HW >::enable ( )

inlineoverrideprivatevirtual

function to enable device

Implements Node.

Definition at line 294 of file BitBangI2C.hxx.

◆ state_recovery()

template<class HW >

bool BitBangI2C< HW >::state_recovery ( )

inlineprivate

Execute recovery state machine.

Returns: true if the sub-state machine is finished, after doing the work required by the current tick.

Definition at line 751 of file BitBangI2C.hxx.

◆ state_rx()

template<class HW >

bool BitBangI2C< HW >::state_rx	(	uint8_t *	data,
		bool	nack
	)

inlineprivate

Execute data RX state machine.

Parameters

location	to shift data into
nack	send a NACK in the (N)ACK slot

Returns: true if the sub-state machine is finished, after doing the work required by the current tick.

Definition at line 667 of file BitBangI2C.hxx.

◆ state_start()

template<class HW >

bool BitBangI2C< HW >::state_start ( )

inlineprivate

Execute state machine for sending start condition.

Returns: true if the sub-state machine is finished, after doing the work required by the current tick.

Definition at line 523 of file BitBangI2C.hxx.

◆ state_stop()

template<class HW >

bool BitBangI2C< HW >::state_stop ( )

inlineprivate

Execute state machine for sending the stop condition.

Returns: true if the sub-state machine is finished, after doing the work required by the current tick.

Definition at line 548 of file BitBangI2C.hxx.

◆ state_tx()

template<class HW >

bool BitBangI2C< HW >::state_tx ( uint8_t data )

inlineprivate

Execute data TX state machine.

Parameters

data	value to send

Returns: true if the sub-state machine is finished, after doing the work required by the current tick. count_ may be negative to indicate an error.

Definition at line 572 of file BitBangI2C.hxx.

◆ tick_interrupt()

template<class HW >

void BitBangI2C< HW >::tick_interrupt ( )

inline

Called at a periodic tick, when enabled.

Todo:: only supporting 7-bit I2C addresses at the moment.

Definition at line 390 of file BitBangI2C.hxx.

◆ transfer()

template<class HW >

int BitBangI2C< HW >::transfer	(	struct i2c_msg *	msg,
		bool	stop
	)

inlineoverrideprivatevirtual

Method to transmit/receive the data.

Parameters

msg	message to transact.
stop	produce a stop condition at the end of the transfer

Returns: bytes transfered upon success or -1 with errno set

Implements I2C.

Definition at line 794 of file BitBangI2C.hxx.

Member Data Documentation

◆ clockStretchActive_

template<class HW >

bool BitBangI2C< HW >::clockStretchActive_

private

true if the slave is clock stretching.

Definition at line 316 of file BitBangI2C.hxx.

◆ count_

template<class HW >

int BitBangI2C< HW >::count_

private

the count of data bytes transferred, error if < 0

Definition at line 305 of file BitBangI2C.hxx.

◆ msg_

template<class HW >

struct i2c_msg* BitBangI2C< HW >::msg_

private

I2C message to presently act upon

Definition at line 303 of file BitBangI2C.hxx.

◆ sem_

template<class HW >

OSSem BitBangI2C< HW >::sem_

private

semaphore to wakeup task level from ISR

Definition at line 304 of file BitBangI2C.hxx.

◆ state_

template<class HW >

State BitBangI2C< HW >::state_

private

state machine state

Definition at line 306 of file BitBangI2C.hxx.

◆ stateRecovery_

template<class HW >

StateRecovery BitBangI2C< HW >::stateRecovery_

I2C recovery state machine state.

Definition at line 313 of file BitBangI2C.hxx.

◆ stateRx_

template<class HW >

StateRx BitBangI2C< HW >::stateRx_

I2C data RX state machine state.

Definition at line 312 of file BitBangI2C.hxx.

◆ stateStart_

template<class HW >

StateStart BitBangI2C< HW >::stateStart_

I2C start state machine state.

Definition at line 309 of file BitBangI2C.hxx.

◆ stateStop_

template<class HW >

StateStop BitBangI2C< HW >::stateStop_

I2C stop state machine state.

Definition at line 310 of file BitBangI2C.hxx.

◆ stateTx_

template<class HW >

StateTx BitBangI2C< HW >::stateTx_

I2C data TX state machine state.

Definition at line 311 of file BitBangI2C.hxx.

◆ stop_

template<class HW >

bool BitBangI2C< HW >::stop_

private

if true, issue stop condition at the end of the message

Definition at line 315 of file BitBangI2C.hxx.

The documentation for this class was generated from the following file:

BitBangI2C.hxx

Public Member Functions

Private Member Functions

Private Attributes

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ BitBangI2C()

◆ ~BitBangI2C()

Member Function Documentation

◆ disable()

◆ enable()

◆ state_recovery()

◆ state_rx()

◆ state_start()

◆ state_stop()

◆ state_tx()

◆ tick_interrupt()

◆ transfer()

Member Data Documentation

◆ clockStretchActive_

◆ count_

◆ msg_

◆ sem_

◆ state_

◆ stateRecovery_

◆ stateRx_

◆ stateStart_

◆ stateStop_

◆ stateTx_

◆ stop_