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