I2C(3)I2C(3)NAMEi2c - 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 hexadecimal) 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 specification 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 fol‐
lowing 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 subad‐
dressing. 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 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
I2C(3)
