ref: b502a62da2ec6058923db94f87ecc2d29db2fa77
dir: /man/3/i2c/
.TH I2C 3 .SH NAME i2c \- basic I2C interface .SH SYNOPSIS .B bind -a .BI #J n .B /dev .PP .BI /dev/i2c. n .ctl . br .BI /dev/i2c. n .data .fi .SH DESCRIPTION .I I2c serves a one-level directory with two files that give access to the target device with address .I n (given in hexadecimal) on the system's I2C bus. .I 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. .PP The control file .BI 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: .TP .B a10 Force 10-bit addressing instead of 7-bit addressing. Otherwise 10-bit addressing is used only if the device address .I n is bigger than 255. .TP .BI size " nbytes" .br Set the logical size of the target device to .IR 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 .B Sys->stat as the length of the data file. .TP .BI subaddress " \fR[\fP n \fR]\fP" .br Cause subsequent reads and writes on the data file to use I2C subaddressing with .I n byte subaddresses (default: 1 byte). .I N must be no larger than 4. The target device must support subaddressing. By default, the device is not subaddressed. Setting .I n to zero switches off subaddressing. .PP When read, the control file displays the current settings. .PP The data file .BI i2c. n .data can be read or written to exchange data with the slave device with address .I n (where .I 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. .SH SOURCE .B /os/port/devi2c.c .br .B /os/*/i2c.c .br .B /os/cerf405/iic.c