IIC(9)                 NetBSD Kernel Developer's Manual                 IIC(9)

NAME
     iic_acquire_bus, iic_release_bus, iic_exec, iic_smbus_write_byte,
     iic_smbus_read_byte, iic_smbus_receive_byte -- Inter IC (I2C) bus

SYNOPSIS
     #include <dev/i2c/i2cvar.h>

     int
     iic_acquire_bus(i2c_tag_t ic, int flags);

     int
     iic_release_bus(i2c_tag_t ic, int flags);

     int
     iic_exec(i2c_tag_t ic, i2c_op_t op, i2c_addr_t addr, const void *cmdbuf,
         size_t cmdlen, void *buf, size_t buflen, int flags);

     int
     iic_smbus_write_byte(i2c_tag_t ic, i2c_addr_t addr, uint8_t cmd,
         uint8_t data, int flags);

     int
     iic_smbus_read_byte(i2c_tag_t ic, i2c_addr_t addr, uint8_t cmd,
         uint8_t *datap, int flags);

     int
     iic_smbus_receive_byte(i2c_tag_t ic, i2c_addr_t addr, uint8_t *datap,
         int flags);

DESCRIPTION
     I2C is a two-wire bus developed by Philips used for connecting integrated
     circuits.  It is commonly used for connecting devices such as EEPROMs,
     temperature sensors, fan controllers, real-time clocks, tuners, and other
     types of integrated circuits.  The iic interface provides a means of com-
     municating with I2C-connected devices.  The System Management Bus, or
     SMBus, is a variant of the I2C bus with a simplified command protocol and
     some electrical differences.

DATA TYPES
     Drivers for devices attached to the I2C bus will make use of the follow-
     ing data types:

     i2c_tag_t   Controller tag for the I2C bus.  This is a pointer to a
                 struct i2c_controller, consisting of function pointers filled
                 in by the I2C controller driver.

     i2c_op_t    I2C bus operation.  The following I2C bus operations are
                 defined:

                 I2C_OP_READ
                       Perform a read operation.

                 I2C_OP_READ_WITH_STOP
                       Perform a read operation and send a STOP condition on
                       the I2C bus at the conclusion of the read.

                 I2C_OP_WRITE
                       Perform a write operation.

                 I2C_OP_WRITE_WITH_STOP
                       Perform a write operation and send a STOP condition on
                       the I2C bus at the conclusion of the write.

     i2c_addr_t  I2C device address.

     struct i2c_attach_args
                 Devices are attached to an I2C bus using this structure.  The
                 structure is defined as follows:

                 struct i2c_attach_args {
                         i2c_tag_t ia_tag;       /* controller */
                         i2c_addr_t ia_addr;     /* address of device */
                         int ia_size;            /* size (for EEPROMs) */
                 };

FUNCTIONS
     The following functions comprise the API provided to drivers of I2C-con-
     nected devices:

     iic_acquire_bus(ic, flags)
               Acquire an exclusive lock on the I2C bus.  This is required
               since only one device may communicate on the I2C bus at a time.
               Drivers should acquire the bus lock, perform the I2C bus opera-
               tions necessary, and then release the bus lock.  Passing the
               I2C_F_POLL flag indicates to iic_acquire_bus() that sleeping is
               not permitted.

     iic_release_bus(ic, flags)
               Release an exclusive lock on the I2C bus.  If the I2C_F_POLL
               flag was passed to iic_acquire_bus(), it must also be passed to
               iic_release_bus().

     iic_exec(ic, op, addr, cmdbuf, cmdlen, buf, buflen, flags)
               Perform a series of I2C transactions on the bus.  iic_exec()
               initiates the operation by sending a START condition on the I2C
               bus and then transmitting the address of the target device
               along with the transaction type.  If cmdlen is non-zero, the
               command pointed to by cmdbuf is then sent to the device.  If
               buflen is non-zero, iic_exec() will then transmit or receive
               the data, as indicated by op.  If op indicates a read opera-
               tion, iic_exec() will send a REPEATED START before transferring
               the data.  If op so indicates, a STOP condition will be sent on
               the I2C bus at the conclusion of the operation.  Passing the
               I2C_F_POLL flag indicates to iic_exec() that sleeping is not
               permitted.

     iic_smbus_write_byte(ic, addr, cmd, data, flags)
               Perform an SMBus WRITE BYTE operation.  This is equivalent to
               I2C_OP_WRITE_WITH_STOP with cmdlen of 1 and buflen of 1.

     iic_smbus_read_byte(ic, addr, cmd, datap, flags)
               Perform an SMBus READ BYTE operation.  This is equivalent to
               I2C_OP_READ_WITH_STOP with cmdlen of 1 and buflen of 1.

     iic_smbus_receive_byte(ic, addr, datap, flags)
               Perform an SMBus RECEIVE BYTE operation.  This is equivalent to
               I2C_OP_READ_WITH_STOP with cmdlen of 0 and buflen of 1.

CONTROLLER INTERFACE
     The I2C controller driver must fill in the function pointers of an
     i2c_controller structure, which is defined as follows:

     struct i2c_controller {
             void    *ic_cookie;     /* controller private */

             int     (*ic_acquire_bus)(void *, int);
             void    (*ic_release_bus)(void *, int);

             int     (*ic_exec)(void *, i2c_op_t, i2c_addr_t,
                        const void *, size_t, void *, size_t, int);

             int     (*ic_send_start)(void *, int);
             int     (*ic_send_stop)(void *, int);
             int     (*ic_initiate_xfer)(void *, i2c_addr_t, int);
             int     (*ic_read_byte)(void *, uint8_t *, int);
             int     (*ic_write_byte)(void *, uint8_t, int);
     };

     The (*ic_acquire_bus)() and (*ic_release_bus)() functions must always be
     provided.

     The controller driver may elect to provide an (*ic_exec)() function.
     This function is intended for use by automated controllers that do not
     provide manual control over I2C bus conditions such as START and STOP.

     If the (*ic_exec)() function is not provided, the following 5 functions
     will be used by iic_exec() in order to execute the I2C bus operation:

     (*ic_send_start)(cookie, flags)
           Send a START condition on the I2C bus.  The I2C_F_POLL flag indi-
           cates that sleeping is not permitted.

     (*ic_send_stop)(cookie, flags)
           Send a STOP condition on the I2C bus.  The I2C_F_POLL flag indi-
           cates that sleeping is not permitted.

     (*ic_initiate_xfer)(cookie, addr, flags)
           Initiate a transfer on the I2C bus by sending a START condition and
           then transmitting the I2C device address and transfer type.  The
           I2C_F_READ flag indicates a read transfer; the lack of this flag
           indicates a write transfer.  The I2C_F_POLL flag indicates that
           sleeping is not permitted.  The error code ETIMEDOUT should be
           returned if a timeout that would indicate that the device is not
           present occurs.

     (*ic_read_byte)(cookie, datap, flags)
           Read a byte from the I2C bus into the memory location referenced by
           datap.  The I2C_F_LAST flag indicates that this is the final byte
           of the transfer, and that a NACK condition should be sent on the
           I2C bus following the transfer of the byte.  The I2C_F_STOP flag
           indicates that a STOP condition should be sent on the I2C bus fol-
           lowing the transfer of the byte.  The I2C_F_POLL flag indicates
           that sleeping is not permitted.

     (*ic_write_byte)(cookie, data, flags)
           Write the byte contained in data to the I2C bus.  The I2C_F_STOP
           flag indicates that a STOP condition should be sent on the I2C bus
           following the transfer of the byte.  The I2C_F_POLL flag indicates
           that sleeping is not permitted.

SEE ALSO
     iic(4), i2cscan(8)

     NXP Semiconductors, I2C-bus Specification and User Manual, Revision 03,
     http://www.ics.nxp.com/support/documents/i2c/pdf/i2c.bus.specification.pdf,
     June 19, 2007.

     Duracell Inc. et. al., System Management Bus (SMBus) Specification,
     Version 2.0, http://smbus.org/specs/smbus20.pdf, August 3, 2000.

HISTORY
     The iic API first appeared in NetBSD 2.0.  OpenBSD support was added in
     OpenBSD 3.6.

AUTHORS
     The iic API was written by Steve C. Woodford and Jason R. Thorpe for
     NetBSD and then ported to OpenBSD by Alexander Yurchenko
     <grange@openbsd.org>.

NetBSD 6.1.5                   October 15, 2011                   NetBSD 6.1.5

You can also request any man page by name and (optionally) by section:

Command: 
Section: 
Architecture: 
Collection: 
 

Use the DEFAULT collection to view manual pages for third-party software.


©1994 Man-cgi 1.15, Panagiotis Christias <christia@softlab.ntua.gr>
©1996-2014 Modified for NetBSD by Kimmo Suominen