i2c - basic I2C interface bind -a #J n /dev

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

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 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 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.

/os/port/devi2c.c

/os/*/i2c.c

/os/cerf405/iic.c