How do I use owfs to read an iButton temperature logger?

Question

I've installed owfs and am trying to read the data off a iButton temperature logger.

owfs lets me mount the iButton as a fuse filesystem and I can see all the data. I'm having trouble figuring out what is the best way to access the data though. I can get individual readings by catting the files, e.g. cat onewire/{deviceid}/log/temperature.1, but the onewire/{deviceid}/log/temperature.ALL file is "broken" (possible too large, as histogram/temperature.ALL work fine).

A python script to read all files seems to work but takes a very long time. Is there a better way to do it? Does anyone have any examples?

I'm using Ubuntu 8.04 and couldn't get the java "one wire viewer" app to run.

Update: Using owpython (installed with owfs), I can get the current temperature but can't figure out how to get access to the recorded logs:

>>> import ow
>>> ow.init("u") # initialize USB
>>> ow.Sensor("/").sensorList()
[Sensor("/81.7FD921000000"), Sensor("/21.C4B912000000")]
>>> x = ow.Sensor("/21.C4B912000000")
>>> print x.type, x.temperature
DS1921           22

x.log gives an AttributeError.

Answer 1

I don't think there is a clever way. owpython doesn't support that telling from the API documentation. I guess /proc is your safest bet. Maybe have a look at the source of the owpython module and check if you can find out how it works.

Answer 2

I've also had problems with owfs. I found it to be an overengineered solution to what is a simple problem. Now I'm using the DigiTemp code without a problem. I found it to be flexible and reliable. For instance, I store the room's temperature in a log file every minute by running

/usr/local/bin/digitemp_DS9097U -c /usr/local/etc/digitemp.conf \
    -q -t0 -n0 -d60 -l/var/log/temperature

To reach that point I downloaded the source file, untarred it and then did the following.

# Compile the hardware-specific command
make ds9097u
# Initialize the configuration file
./digitemp_DS9097U -s/dev/ttyS0 -i
# Run command to obtain temperature, and verify your setup
./digitemp_DS9097U -a 
# Copy the configuration file to an accessible place
cp .digitemprc /usr/local/etc/digitemp.conf

I also hand-edited my configuration file to adjust it to my setup. This is how it ended-up.

TTY /dev/ttyS0
READ_TIME 1000
LOG_TYPE 1
LOG_FORMAT "%b %d %H:%M:%S Sensor %s C: %.2C F: %.2F"
CNT_FORMAT "%b %d %H:%M:%S Sensor %s #%n %C"
HUM_FORMAT "%b %d %H:%M:%S Sensor %s C: %.2C F: %.2F H: %h%%"
SENSORS 1
ROM 0 0x10 0xD3 0x5B 0x07 0x00 0x00 0x00 0x05

In my case I also created a /etc/init.d/digitemp file and enabled it to run at startup.

#! /bin/sh
#
# System startup script for the temperature monitoring daemon
#
### BEGIN INIT INFO
# Provides: digitemp
# Required-Start:
# Should-Start:
# Required-Stop:
# Should-Stop:
# Default-Start:  2 3 5
# Default-Stop:   0 1 6
# Description:    Start the temperature monitoring daemon
### END INIT INFO

DIGITEMP=/usr/local/bin/digitemp_DS9097U
test -x $DIGITEMP || exit 5

DIGITEMP_CONFIG=/root/digitemp.conf
test -f $DIGITEMP_CONFIG || exit 6

DIGITEMP_LOGFILE=/var/log/temperature

# Source SuSE config
. /etc/rc.status

rc_reset
case "$1" in
    start)
        echo -n "Starting temperature monitoring daemon"
        startproc $DIGITEMP -c $DIGITEMP_CONFIG  -q -t0 -n0 -d60 -l$DIGITEMP_LOGFILE
        rc_status -v
        ;;
    stop)
        echo -n "Shutting down temperature monitoring daemon"
        killproc -TERM $DIGITEMP
        rc_status -v
        ;;
    try-restart)
        $0 status >/dev/null && $0 restart
        rc_status
        ;;
    restart)
        $0 stop
        $0 start
        rc_status
        ;;
    force-reload)
        $0 try-restart
        rc_status
        ;;
    reload)
        $0 try-restart
        rc_status
        ;;
    status)
        echo -n "Checking for temperature monitoring service"
        checkproc $DIGITEMP
        rc_status -v
        ;;
    *)
        echo "Usage: $0 {start|stop|status|try-restart|restart|force-reload|reload}"
        exit 1
        ;;
esac
rc_exit

Answer 3

This is crazy complicated. Has anybody figured out a SIMPLE way to do this? I used to be able to get the onewire viewer to work in Windows, but I can't get it to work in Ubuntu. The OWFS just plain confounds me, and digitemp is no better. All that configuration for such a simple little device? I can interface with my mobile phone with less config than that!

Any smart solutions out there?

Answer 4

Well I have just started to look at ibuttons and want to use python.

This looks more promising:

http://www.ohloh.net/p/pyonewire