Detailed Description

I2C driver interface.

============================================================================

The I2C header file should be included in an application as follows:

Operation

The I2C driver operates as a master on a single-master I2C bus in either I2C_MODE_BLOCKING or I2C_MODE_CALLBACK. In blocking mode, the task's execution is blocked during the I2C transaction. When the transfer has completed, code execution will resume. In callback mode, the task's execution is not blocked, allowing for other transactions to be queued up or to process some other code. When the transfer has completed, the I2C driver will call a user-specified callback function (from a HWI or SWI context, depending on the device).

The APIs in this driver serve as an interface to a typical TI-RTOS application. The specific peripheral implementations are responsible to create all the SYS/BIOS specific primitives to allow for thread-safe operation.

Opening the driver

I2C_Handle      handle;
I2C_Params      params;
I2C_Transaction i2cTransaction;
I2C_Params_init(&params);
params.transferMode  = I2C_MODE_CALLBACK;
params.transferCallbackFxn = someI2CCallbackFunction;
handle = I2C_open(someI2C_configIndexValue, &params);
if (!handle) {
    System_printf("I2C did not open");
}

Transferring data

A I2C transaction with a I2C peripheral is started by calling I2C_transfer(). The details of the I2C transaction is specified with a I2C_Transaction data structure. This structure allows for any of the three types of transactions: Write, Read, or Write/Read. Each transfer is performed atomically with the I2C slave peripheral.

I2C_Transaction i2cTransaction;
i2cTransaction.writeBuf = someWriteBuffer;
i2cTransaction.writeCount = numOfBytesToWrite;
i2cTransaction.readBuf = someReadBuffer;
i2cTransaction.readCount = numOfBytesToRead;
i2cTransaction.slaveAddress = some7BitI2CSlaveAddress;
ret = I2C_transfer(handle, &i2cTransaction);
if (!ret) {
    System_printf("Unsuccessful I2C transfer");
}

Implementation

This module serves as the main interface for TI-RTOS applications. Its purpose is to redirect the module's APIs to specific peripheral implementations which are specified using a pointer to a I2C_FxnTable.

The I2C driver interface module is joined (at link time) to a NULL-terminated array of I2C_Config data structures named I2C_config. I2C_config is implemented in the application with each entry being an instance of a I2C peripheral. Each entry in I2C_config contains a:

(I2C_FxnTable *) to a set of functions that implement a I2C peripheral
(void *) data object that is associated with the I2C_FxnTable
(void *) hardware attributes that are associated to the I2C_FxnTable

Instrumentation

The I2C driver interface produces log statements if instrumentation is enabled.

Diagnostics Mask	Log details
Diags_USER1	basic operations performed
Diags_USER2	detailed operations performed

#include <stdint.h>
#include <stdbool.h>
#include <stddef.h>

Include dependency graph for I2C.h:

This graph shows which files directly or indirectly include this file:

Go to the source code of this file.

Data Structures
struct	I2C_Transaction
	I2C transaction. More...

struct	I2C_Params
	I2C Parameters. More...

struct	I2C_FxnTable
	The definition of a I2C function table that contains the required set of functions to control a specific I2C driver implementation. More...

struct	I2C_Config
	I2C Global configuration. More...

Macros
#define	I2C_CMD_RESERVED 32

#define	I2C_STATUS_RESERVED -32

#define	I2C_STATUS_SUCCESS 0
	Successful status code returned by I2C_control(). More...

#define	I2C_STATUS_ERROR -1
	Generic error status code returned by I2C_control(). More...

#define	I2C_STATUS_UNDEFINEDCMD -2
	An error status code returned by I2C_control() for undefined command codes. More...

Typedefs
typedef struct I2C_Config *	I2C_Handle
	A handle that is returned from a I2C_open() call. More...

typedef struct I2C_Transaction	I2C_Transaction
	I2C transaction. More...

typedef enum I2C_TransferMode	I2C_TransferMode
	I2C transfer mode. More...

typedef void(*	I2C_CallbackFxn) (I2C_Handle, I2C_Transaction *, bool)
	I2C callback function. More...

typedef enum I2C_BitRate	I2C_BitRate
	I2C bitRate. More...

typedef struct I2C_Params	I2C_Params
	I2C Parameters. More...

typedef void(*	I2C_CloseFxn) (I2C_Handle handle)
	A function pointer to a driver specific implementation of I2C_close(). More...

typedef int(*	I2C_ControlFxn) (I2C_Handle handle, unsigned int cmd, void *arg)
	A function pointer to a driver specific implementation of I2C_control(). More...

typedef void(*	I2C_InitFxn) (I2C_Handle handle)
	A function pointer to a driver specific implementation of I2C_init(). More...

typedef I2C_Handle(*	I2C_OpenFxn) (I2C_Handle handle, I2C_Params *params)
	A function pointer to a driver specific implementation of I2C_open(). More...

typedef bool(*	I2C_TransferFxn) (I2C_Handle handle, I2C_Transaction *transaction)
	A function pointer to a driver specific implementation of I2C_transfer(). More...

typedef struct I2C_FxnTable	I2C_FxnTable
	The definition of a I2C function table that contains the required set of functions to control a specific I2C driver implementation. More...

typedef struct I2C_Config	I2C_Config
	I2C Global configuration. More...

Enumerations
enum	I2C_TransferMode { I2C_MODE_BLOCKING, I2C_MODE_CALLBACK }
	I2C transfer mode. More...

enum	I2C_BitRate { I2C_100kHz = 0, I2C_400kHz = 1 }
	I2C bitRate. More...

Functions
void	I2C_close (I2C_Handle handle)
	Function to close a I2C peripheral specified by the I2C handle. More...

int	I2C_control (I2C_Handle handle, unsigned int cmd, void *arg)
	Function performs implementation specific features on a given I2C_Handle. More...

void	I2C_init (void)
	Function to initializes the I2C module. More...

I2C_Handle	I2C_open (unsigned int index, I2C_Params *params)
	Function to initialize a given I2C peripheral specified by the particular index value. The parameter specifies which mode the I2C will operate. More...

void	I2C_Params_init (I2C_Params *params)
	Function to initialize the I2C_Params struct to its defaults. More...

bool	I2C_transfer (I2C_Handle handle, I2C_Transaction *transaction)
	Function to perform an I2C transaction with an I2C slave peripheral. More...

Typedef Documentation

typedef struct I2C_Config* I2C_Handle

A handle that is returned from a I2C_open() call.

typedef struct I2C_Transaction I2C_Transaction

I2C transaction.

This structure defines the nature of the I2C transaction. This structure specifies the buffer and buffer's size that is to be written to or read from the I2C slave peripheral. arg is an optional user supplied argument that will be passed to the callback function when the I2C driver is in I2C_MODE_CALLBACK. nextPtr is to be only used by the I2C driver.

typedef enum I2C_TransferMode I2C_TransferMode

I2C transfer mode.

I2C_MODE_BLOCKING block task execution while a I2C transfer is in progress I2C_MODE_CALLBACK does not block task execution; but calls a callback function when the I2C transfer has completed

typedef void(* I2C_CallbackFxn) (I2C_Handle, I2C_Transaction *, bool)

I2C callback function.

User definable callback function prototype. The I2C driver will call the defined function and pass in the I2C driver's handle, the pointer to the I2C transaction that just completed, and the return value of I2C_transfer.

Parameters

I2C_Handle	I2C_Handle
I2C_Transaction*	Address of the I2C_Transaction performed
bool	Results of the I2C transaction

typedef enum I2C_BitRate I2C_BitRate

I2C bitRate.

Specify one of the standardized I2C bus bit rates for I2C communications. The default is I2C_100kHz.

typedef struct I2C_Params I2C_Params

I2C Parameters.

I2C parameters are used to with the I2C_open() call. Default values for these parameters are set using I2C_Params_init().

If I2C_TransferMode is set to I2C_MODE_BLOCKING then I2C_transfer function calls will block thread execution until the transaction has completed.

If I2C_TransferMode is set to I2C_MODE_CALLBACK then I2C_transfer will not block thread execution and it will call the function specified by transferCallbackFxn. Sequential calls to I2C_transfer in I2C_MODE_CALLBACK mode will put the designated transaction onto an internal queue that automatically starts queued transactions after the previous transaction has completed. (regardless of error state).

I2C_BitRate specifies the I2C bus rate used for I2C communications.

See also: I2C_Params_init()

typedef void(* I2C_CloseFxn) (I2C_Handle handle)

A function pointer to a driver specific implementation of I2C_close().

typedef int(* I2C_ControlFxn) (I2C_Handle handle, unsigned int cmd, void *arg)

A function pointer to a driver specific implementation of I2C_control().

typedef void(* I2C_InitFxn) (I2C_Handle handle)

A function pointer to a driver specific implementation of I2C_init().

typedef I2C_Handle(* I2C_OpenFxn) (I2C_Handle handle, I2C_Params *params)

A function pointer to a driver specific implementation of I2C_open().

typedef bool(* I2C_TransferFxn) (I2C_Handle handle, I2C_Transaction *transaction)

A function pointer to a driver specific implementation of I2C_transfer().

typedef struct I2C_FxnTable I2C_FxnTable

The definition of a I2C function table that contains the required set of functions to control a specific I2C driver implementation.

typedef struct I2C_Config I2C_Config

I2C Global configuration.

The I2C_Config structure contains a set of pointers used to characterize the I2C driver implementation.

This structure needs to be defined before calling I2C_init() and it must not be changed thereafter.

See also: I2C_init()

Enumeration Type Documentation

enum I2C_TransferMode

I2C transfer mode.

I2C_MODE_BLOCKING block task execution while a I2C transfer is in progress I2C_MODE_CALLBACK does not block task execution; but calls a callback function when the I2C transfer has completed

Enumerator
I2C_MODE_BLOCKING	I2C_transfer blocks execution
I2C_MODE_CALLBACK	I2C_transfer queues transactions and does not block

enum I2C_BitRate

I2C bitRate.

Specify one of the standardized I2C bus bit rates for I2C communications. The default is I2C_100kHz.

Enumerator
I2C_100kHz
I2C_400kHz

Function Documentation

void I2C_close ( I2C_Handle handle )

Function to close a I2C peripheral specified by the I2C handle.

Precondition: I2C_open() had to be called first.

Parameters

handle A I2C_Handle returned from I2C_open

See also: I2C_open()

int I2C_control	(	I2C_Handle	handle,
		unsigned int	cmd,
		void *	arg
	)

Function performs implementation specific features on a given I2C_Handle.

Commands for I2C_control can originate from I2C.h or from implementation specific I2C*.h (I2CCC26XX.h, I2CTiva.h, etc.. ) files. While commands from I2C.h are API portable across driver implementations, not all implementations may support all these commands. Conversely, commands from driver implementation specific I2C*.h files add unique driver capabilities but are not API portable across all I2C driver implementations.

Commands supported by I2C.h follow a I2C_CMD_<cmd> naming convention.
Commands supported by I2C*.h follow a I2C*_CMD_<cmd> naming convention.
Each control command defines arg differently. The types of arg are documented with each command.

See I2C_control command codes for command codes.

See I2C_control return status codes for status codes.

Precondition: I2C_open() has to be called first.

Parameters

handle	A I2C handle returned from I2C_open()
cmd	I2C.h or I2C*.h commands.
arg	An optional R/W (read/write) command argument accompanied with cmd

Returns: Implementation specific return codes. Negative values indicate unsuccessful operations.

See also: I2C_open()

void I2C_init ( void )

Function to initializes the I2C module.

Precondition: The I2C_config structure must exist and be persistent before this function can be called. This function must also be called before any other I2C driver APIs. This function call does not modify any peripheral registers.

I2C_Handle I2C_open	(	unsigned int	index,
		I2C_Params *	params
	)

Function to initialize a given I2C peripheral specified by the particular index value. The parameter specifies which mode the I2C will operate.

Precondition: I2C controller has been initialized

Parameters

index	Logical peripheral number for the I2C indexed into the I2C_config table
params	Pointer to an parameter block, if NULL it will use default values. All the fields in this structure are RO (read-only).

Returns: A I2C_Handle on success or a NULL on an error or if it has been opened already.

See also: I2C_init(); I2C_close()

void I2C_Params_init ( I2C_Params * params )

Function to initialize the I2C_Params struct to its defaults.

Parameters

params An pointer to I2C_Params structure for initialization

Defaults values are: transferMode = I2C_MODE_BLOCKING transferCallbackFxn = NULL bitRate = I2C_100kHz

bool I2C_transfer	(	I2C_Handle	handle,
		I2C_Transaction *	transaction
	)

Function to perform an I2C transaction with an I2C slave peripheral.

This function will start a I2C transfer and can only be called from a Task context when in I2C_MODE_BLOCKING. The I2C transfer procedure starts with evaluating how many bytes are to be written and how many are to be read from the I2C peripheral. Due to common I2C data transfer processes, to be written will always sent before any data is read.

The data written to the peripheral is preceded with the peripheral's 7-bit I2C slave address (with the Write bit set). After all the data has been transmitted, the driver will evaluate if any data needs to be read from the device. If so, a Re-START bit is sent, along with the same 7-bit I2C slave address (with the Read bit). Else, the transfer is concluded with a STOP bit. After the specified number of bytes have been read by the I2C, the transfer is ended with a NACK and STOP bit.

In I2C_MODE_BLOCKING, I2C_transfer will block task execution until the transaction has completed.

In I2C_MODE_CALLBACK, I2C_transfer does not block task execution and calls a callback function specified by transferCallbackFxn when the transfer completed. Success or failure of the transaction is determined via the callback function's bool argument. If a transfer is already taking place, the transaction is put on an internal queue. The queue is serviced in a first come first served basis. The I2C_Transaction structure must stay persistent until the I2C_transfer function has completed!

Parameters

handle	A I2C_Handle
transaction	A pointer to a I2C_Transaction. All of the fields within transaction are WO (write-only) unless otherwise noted in the driver implementations.

Returns: In I2C_MODE_BLOCKING: true on successful transfer; false on an error, such as an I2C bus fault (NACK). In I2C_MODE_CALLBACK: always true. The transferCallbackFxn's bool argument will be true if successful; false on an error, such as an I2C bus fault (NACK).

See also: I2C_open

Detailed Description

Operation

Opening the driver

Transferring data

Implementation

Instrumentation

Data Structures

Macros

Typedefs

Enumerations

Functions

Typedef Documentation

Enumeration Type Documentation

Function Documentation