| .TH I2CSET 8 "November 2008" |
| .SH "NAME" |
| i2cset \- set I2C registers |
| |
| .SH SYNOPSIS |
| .B i2cset |
| .RB [ -f ] |
| .RB [ -y ] |
| .RB [ "-m mask" ] |
| .RB [ -r ] |
| .I i2cbus |
| .I chip-address |
| .I data-address |
| .RI [ "value " [ "mode" ]] |
| .br |
| .B i2cset |
| .B -V |
| |
| .SH DESCRIPTION |
| i2cset is a small helper program to set registers visible through the I2C |
| bus. |
| |
| .SH OPTIONS |
| .TP |
| .B -V |
| Display the version and exit. |
| .TP |
| .B -f |
| Force access to the device even if it is already busy. By default, i2cset |
| will refuse to access a device which is already under the control of a |
| kernel driver. Using this flag is dangerous, it can seriously confuse the |
| kernel driver in question. It can also cause i2cset to silently write to |
| the wrong register. So use at your own risk and only if you know what |
| you're doing. |
| .TP |
| .B -y |
| Disable interactive mode. By default, i2cset will wait for a confirmation |
| from the user before messing with the I2C bus. When this flag is used, it |
| will perform the operation directly. This is mainly meant to be used in |
| scripts. |
| .TP |
| .B -m mask |
| The \fImask\fR parameter, if specified, describes which bits of \fIvalue\fR |
| will be actually written to \fIdata-address\fR. Bits set to 1 in the mask |
| are taken from \fIvalue\fR, while bits set to 0 will be read from |
| \fIdata-address\fR and thus preserved by the operation. Please note that |
| this parameter assumes that the read and write operations for the specified |
| mode are symmetrical for the device you are accessing. This may or may not |
| be the case, as neither I2C nor SMBus guarantees this. |
| .TP |
| .B -r |
| Read back the value right after writing it, and compare the result with the |
| value written. This used to be the default behavior. The same limitations |
| apply as those of option \fB-m\fR. |
| .PP |
| There are three required options to i2cset. \fIi2cbus\fR indicates the number |
| or name of the I2C bus to be scanned. This number should correspond to one of |
| the busses listed by \fIi2cdetect -l\fR. \fIchip-address\fR specifies the |
| address of the chip on that bus, and is an integer between 0x03 and 0x77. |
| \fIdata-address\fR specifies the address on that chip to write to, and is an |
| integer between 0x00 and 0xFF. |
| .PP |
| The \fIvalue\fR parameter, if specified, is the value to write to that |
| location on the chip. If this parameter is omited, then a short write is |
| issued. For most chips, it simply sets an internal pointer to the target |
| location, but doesn't actually write to that location. For a few chips |
| though, in particular simple ones with a single register, this short write |
| is an actual write. |
| .PP |
| The \fImode\fR parameter, if specified, is one of the letters \fBb\fP or |
| \fBw\fP, corresponding to a write size of a single byte or a 16-bit word, |
| respectively. A \fBp\fP can also be appended to the \fImode\fR parameter to |
| enable PEC. If the \fImode\fR parameter is omitted, i2cset defaults to byte |
| mode without PEC. The \fIvalue\fR provided must be within range for the |
| specified data type (0x00-0xFF for bytes, 0x0000-0xFFFF for words). |
| |
| .SH WARNING |
| i2cset can be extremely dangerous if used improperly. It can confuse your |
| I2C bus, cause data loss, or have more serious side effects. Writing to |
| a serial EEPROM on a memory DIMM (chip addresses between 0x50 and 0x57) may |
| DESTROY your memory, leaving your system unbootable! Be extremely careful |
| using this program. |
| |
| .SH SEE ALSO |
| i2cdump(8), isaset(8) |
| |
| .SH AUTHOR |
| Frodo Looijaard, Mark D. Studebaker and Jean Delvare |
| |
| This manual page was originally written by David Z Maze <dmaze@debian.org> for |
| the Debian GNU/Linux system. |
