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
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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
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