I2C(3)                                                     I2C(3)

     NAME
          i2c - basic I2C interface

     SYNOPSIS
          bind -a #Jn /dev

          /dev/i2c.n.ctl
          /dev/i2c.n.data

     DESCRIPTION
          I2c serves a one-level directory with two files that give
          access to the target device with address n (given in hex-
          adecimal) on the system's I2C bus.  N is usually determined
          by the I2C device manufacturer.  I2C gives address 0 special
          meaning as the `general call' address.  See an I2C specifi-
          cation for details.

          The control file i2c.n.ctl accepts commands to set the valid
          address range and subaddressing mode for the corresponding
          data file.  The following control messages can be written to
          it:

          a10  Force 10-bit addressing instead of 7-bit addressing.
               Otherwise 10-bit addressing is used only if the device
               address n is bigger than 255.

          size nbytes
               Set the logical size of the target device to nbytes.
               (By default when opened, it is 256 bytes, enough for
               most small I2C devices.)  IO requests will be kept
               within this limit.  This value is also returned by
               Sys->stat as the length of the data file.

          subaddress [ n ]
               Cause subsequent reads and writes on the data file to
               use I2C subaddressing with n byte subaddresses
               (default: 1 byte).  N must be no larger than 4.  The
               target device must support subaddressing.  By default,
               the device is not subaddressed.  Setting n to zero
               switches off subaddressing.

          When read, the control file displays the current settings.

          The data file i2c.n.data can be read or written to exchange
          data with the slave device with address n (where n is given
          in hexadecimal).  Each write request transmits the given
          data to the device.  Each read request sends a receive
          request to the device and returns the resulting data.  If
          the I2C target is subaddressed, the current file offset is
          used as the subaddress; otherwise the file offset is

     I2C(3)                                                     I2C(3)

          ignored, and the device typically starts at 0 for each
          transfer request.  Read and write requests are trimmed to
          the declared size of the device.

     SOURCE
          /os/port/devi2c.c
          /os/*/i2c.c
          /os/cerf405/iic.c