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NAMEsmbmsg —
send or receive messages over an SMBus
SYNOPSIS
DESCRIPTIONThesmbmsg utility can be used to send or receive
messages over an SMBus, see
smbus(4).
The Note that probing the bus is risky, since individual devices could perform unwanted actions upon receiving one of the mentioned messages. For example, if a particular SMBus device considers any write operation issued to it as a request to power off the system, the probing would trigger this action. The second form shown in the synopsis can be used to send or receive arbitrary messages to or from individual devices. This might be useful to explore individual devices on the SMBus, or maybe even to write short shell scripts performing maintenance operations on the bus. Any data values on the command-line are integer values in the
range 0 through 255 for byte values, or 0 through 65535 for word values.
They can be specified using standard
‘ Since the low-order bit of the device address of SMBus devices selects between read and write operations, only even-numbered slave addresses can exist on the bus. The options are as follows:
Not all argument combinations make sense in order to form valid
SMBus messages. If no
Note in particular that specifying 0 as a count value has a different meaning than omitting the respective option entirely. If a command value has been given using the
FILES
EXIT STATUSExit status is 0 on success, or according to sysexits(3) in case of failure.EXAMPLESTypical usage examples of thesmbmsg command include:
smbmsg -f /dev/smb1 -p Probe all devices on the SMBus attached to /dev/smb1. smbmsg -s 0x70 -i 1 Issue a receive byte message to the device at address 0x70, and display the received byte using the default format. smbmsg -s 0x70 -c 0xff -i 1 -F
%d Issue a read byte message to the device at slave
address 0x70, using 255 (0xff) as the command-byte to send to the device,
and display the result using the custom format
‘ smbmsg -s 0xa0 -c 0 -o 1
0x80 Send a write byte message to the slave device at address 0xa0, using 0 as the command-byte value, and 0x80 as the byte to send (after the command). Assuming this might be a Philips PCF8583 real-time clock, this would stop the clock. smbmsg -s 0xa0 -c 1 -i 6 -F
%02x Send a block read command to device at address 0xa0, and read 6 bytes from it, using hexadecimal display. Again, assuming a PCF8583 RTC, this would display the fractions of second, seconds, minutes, hours, year/date, and weekday/month values. Since this RTC uses BCD notation, the actual values displayed were decimal then. smbmsg -s 0xa0 -c 2 -o 5 0x00 0x07
0x22 0x16 0x05 Send a block write command to device at address 0xa0. For the PCF8583 RTC, this would set the clock to Sunday (2004%4)-05-16 22:07:00. DIAGNOSTICSDiagnostic messages issued are supposed to be self-explanatory.SEE ALSOprintf(3), sysexits(3), smb(4), smbus(4)The SMBus specification, http://www.smbus.org/specs/. HISTORYThesmbmsg utility first appeared in
FreeBSD 5.3.
AUTHORSThesmbmsg utility and this manual page were written by
Jörg Wunsch.
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