How to Read 1-Wire Temperature Using a NSLU2 With Debian

This is a small Debian NSLU2 1-Wire HowTo that explains the steps needed to get some data out of those small cool devices using a DS18S20 NSLU2 1-Wire setup.

The component covered by green heat shrink in the picture below is a 1-Wire component, specifically a temperature measuring device, model DS18S20:

(18S20 wiring is shown on this page: DS18S20 Wiring )

The 1-Wire bus runs well on both telephone cable and Ethernet cable, and since the DS18S20 was already soldered onto a piece of Ethernet cable and covered in heat shrink, I chose an easy to make test setup by connecting the Ethernet cable to a piece of ordinary telephone cable, because the connector already mounted on the telephone cable fits directly into a DS9490R 1-Wire USB adapter available from hobby-boards.com. It’s the blue device in the picture below:

(See the post called Debian on NSLU2 With USB Hard Disk and Homeplug Network for more details about the rest of the system.)

Paul Alfille wrote a clever piece of software that makes it easy to handle 1-Wire units. It’s called OWFS, and the project has its own website at owfs.org, if you want to know more about how OWFS works. I chose this software to handle the units on my 1-Wire NSLU2 Debian installation, but there’s a bit of work to do to get the 1-Wire software installed and running. Instructions are available at owfs.org / Setup / Install / Download, which points to the project files on SourceForge.net.

In order to get the installation files for OWFS onto the NSLU2 I logged in via my laptop PC using ssh and use wget on NSLU2: (Replace .xx with the address of the NSLU2 on the intranet)

$ ssh thomas@192.168.1.xx

$ mkdir /home/thomas/owfs_install
$ cd /home/thomas/owfs_install
$ wget sourceforge.net/projects/owfs/files/owfs/2.8p13/owfs-2.8p13.tar.gz/download
$ mv download owfs-2.8p13.tar.gz
$ tar -zxvf owfs-2.8p13.tar.gz
$ cd /home/thomas/owfs_install/owfs-2.8p13

For some reason the downloaded file is named download so I use the mv command to rename it to something more precise.

When I try to install OWFS it turns out that I’m missing something on my freshly installed Debian:

$ ./configure

error: no acceptable C compiler found in $PATH

The package build-essential contains the needed C compiler:

$ su
# apt-get install build-essential
# exit

Trying to configure one more time reveals a whole bunch of missing software required for OWFS to compile and run:

$ ./configure

...
configure: WARNING: Cannot find php binary. Install php or php5 package
configure: WARNING: OWPHP is disabled because php binary is not found
configure: WARNING: Cannot find python include-file. Install python-devel package.
configure: WARNING: OWPYTHON is disabled because python include-file is not found
checking for Tcl configuration... configure: WARNING: Can't find Tcl configuration definitions
configure: WARNING: OWTCL is disabled because tclConfig.sh is not found
configure: WARNING: LD_EXTRALIBS= OSLIBS=
configure: WARNING:
Can't find fuse.h - Add the search path with --with-fuseinclude
configure: WARNING: Install FUSE-2.2 or later to enable owfs - download it from http://fuse.sourceforge.net/
configure: WARNING: OWFS is disabled because fuse.h is not found.
configure: WARNING: Can't find libusb
configure: WARNING: libusb not found, usb will be disabled
...
Compile-time options:
USB is DISABLED
Profiling is DISABLED
Tracing memory allocation is DISABLED
1wire bus traffic reports is DISABLED
...
Module configuration:
owfs is DISABLED
swig is DISABLED
owperl is DISABLED
owphp is DISABLED
owpython is DISABLED
owtcl is DISABLED

Fortunately most of the missing stuff is contained in these 7 packages:

$ su
# apt-get install php5-cli python2.4-dev tcl-dev tk-dev libusb-dev swig libperl-dev
# exit

The warning about the missing FUSE software is cleared by downloading and installing like this:

$ mkdir /home/thomas/fuse
$ cd /home/thomas/fuse
$ wget http://sourceforge.net/projects/fuse/files/fuse-2.X/2.8.5/fuse-2.8.5.tar.gz/download
$ mv download fuse-2.8.5.tar.gz
$ tar -zxvf fuse-2.8.5.tar.gz
$ cd /home/thomas/fuse/fuse-2.8.5/
$ ./configure
$ make
$ su
# make install
# exit

Now only one warning is present and a few disabled functions, which is acceptable for the purpose of reading temperature from the DS18S20 IC:

$ cd /home/thomas/owfs_install/owfs-2.8p13

$ ./configure

configure: WARNING: LD_EXTRALIBS= OSLIBS=

Compile-time options:
Profiling is DISABLED
Tracing memory allocation is DISABLED
1wire bus traffic reports is DISABLED

Module configuration:
owlib is enabled
owshell is enabled
owfs is enabled
owhttpd is enabled
owftpd is enabled
owserver is enabled
ownet is enabled
ownetlib is enabled
owtap is enabled
owmon is enabled
owcapi is enabled
swig is enabled
owperl is enabled
owphp is enabled
owpython is enabled
owtcl is enabled

And a final install:

$ make
$ su
# make install
# exit

Note that $ means you are working on the CLI as a normal user, and # means you’re working as root, which should be minimized since you have total power as root which again means that you could easily cause irreversible damage to your system by accident. Therefore it’s best to do as much as you can as a normal user.

Howto access DS9490: FS in OWFS stands for File System so I created a directory for the 1-Wire devices and mounted the one-wire file system in this new directory:

$ mkdir /home/thomas/owfs

$ /opt/owfs/bin/owfs -u /home/thomas/owfs
DEFAULT: owlib.c:SetupSingleInboundConnection(201) Cannot open USB bus master
DEFAULT: owlib.c:LibStart(54) No valid 1-wire buses found

Again, the separation between root and normal users means that as a normal user (thomas) I don’t have direct access to the USB DS9490R adapter, so I have to change to superuser root to mount OWFS:

$ su
# /opt/owfs/bin/owfs -u /home/thomas/owfs
DEFAULT: ow_usb_msg.c:DS9490_open(276) Opened USB DS9490 bus master at 1:4.
DEFAULT: ow_usb_cycle.c:DS9490_ID_this_master(191) Set DS9490 1:4 unique id to 81 59 25 27 00 00 00 CE
# exit

But still more problems related to root versus normal user permissions – the mounted directory containing the 1-Wire data is not available to normal users:

$ ls -la /home/thomas
total 32
drwxr-xr-x 5 thomas thomas 4096 Sep  8 12:44 .
drwxr-xr-x 3 root   root   4096 Sep  2 20:20 ..
-rw------- 1 thomas thomas 1338 Sep  8 12:47 .bash_history
-rw-r--r-- 1 thomas thomas  220 Sep  2 20:20 .bash_logout
-rw-r--r-- 1 thomas thomas 3116 Sep  2 20:20 .bashrc
-rw-r--r-- 1 thomas thomas  675 Sep  2 20:20 .profile
drwxr-xr-x 3 thomas thomas 4096 Sep  8 09:15 fuse
d????????? ? ?      ?         ?            ? owfs
drwxr-xr-x 3 thomas thomas 4096 Sep  7 20:59 owfs_install

and can’t be listed when you’re logged in as a normal user:

$ ls -la /home/thomas/owfs
ls: cannot access owfs: Permission denied

Changing to superuser using su reveals the goodies:

$ su

# ls -la /home/thomas
total 32
drwxr-xr-x 5 thomas thomas 4096 Sep  8 12:44 .
drwxr-xr-x 3 root   root   4096 Sep  2 20:20 ..
-rw------- 1 thomas thomas 1338 Sep  8 12:47 .bash_history
-rw-r--r-- 1 thomas thomas  220 Sep  2 20:20 .bash_logout
-rw-r--r-- 1 thomas thomas 3116 Sep  2 20:20 .bashrc
-rw-r--r-- 1 thomas thomas  675 Sep  2 20:20 .profile
drwxr-xr-x 3 thomas thomas 4096 Sep  8 09:15 fuse
drwxr-xr-x 1 root   root      8 Sep  8 12:51 owfs
drwxr-xr-x 3 thomas thomas 4096 Sep  7 20:59 owfs_install

My OWFS NSLU2 system is up and running, and 10.4F7… is the DS18S20 IC on the 1-Wire bus:

# ls -la /home/thomas/owfs
total 4
drwxr-xr-x 1 root   root      8 Sep  8 12:51 .
drwxr-xr-x 5 thomas thomas 4096 Sep  8 12:44 ..
drwxrwxrwx 1 root   root      8 Sep  8 12:52 10.4F7494010800
drwxrwxrwx 1 root   root      8 Sep  8 12:52 81.592527000000
drwxr-xr-x 1 root   root      8 Sep  8 12:51 alarm
drwxr-xr-x 1 root   root      8 Sep  8 12:51 bus.0
drwxr-xr-x 1 root   root      8 Sep  8 12:51 settings
drwxrwxrwx 1 root   root      8 Sep  8 12:52 simultaneous
drwxr-xr-x 1 root   root      8 Sep  8 12:51 statistics
drwxr-xr-x 1 root   root     32 Sep  8 12:51 structure
drwxr-xr-x 1 root   root      8 Sep  8 12:51 system
drwxr-xr-x 1 root   root      8 Sep  8 12:51 uncached

In order to get access to OWFS as a normal user there’s trick you can do, but first I’m rebooting to make sure OWFS is completely shutdown. (There’s probably a clever way to do this, if you know what you’re doing ;-) ):

# reboot

Log in again from laptop to NSLU2:

$ ssh thomas@192.168.1.xx

The option --allow-other can be added when running OWFS, which allows normal users to access the 1-Wire file system without changing to superuser (the -u option means that you’re connecting via USB adapter instead of a serial connector):

$ su

# /opt/owfs/bin/owfs --allow_other -u /home/thomas/owfs
DEFAULT: ow_usb_msg.c:DS9490_open(276) Opened USB DS9490 bus master at 1:4.
DEFAULT: ow_usb_cycle.c:DS9490_ID_this_master(191) Set DS9490 1:4 unique id to 81 59 25 27 00 00 00 CE
# exit

Now there is access to the owfs directory even when you’re logged in as a normal user:

$ ls -la /home/thomas
total 32
drwxr-xr-x 5 thomas thomas 4096 Sep  8 12:44 .
drwxr-xr-x 3 root   root   4096 Sep  2 20:20 ..
-rw------- 1 thomas thomas 1452 Sep  8 12:57 .bash_history
-rw-r--r-- 1 thomas thomas  220 Sep  2 20:20 .bash_logout
-rw-r--r-- 1 thomas thomas 3116 Sep  2 20:20 .bashrc
-rw-r--r-- 1 thomas thomas  675 Sep  2 20:20 .profile
drwxr-xr-x 3 thomas thomas 4096 Sep  8 09:15 fuse
drwxr-xr-x 1 root   root      8 Sep  8 13:02 owfs
drwxr-xr-x 3 thomas thomas 4096 Sep  7 20:59 owfs_install
$ ls -la /home/thomas/owfs
total 4
drwxr-xr-x 1 root   root      8 Sep  8 13:02 .
drwxr-xr-x 5 thomas thomas 4096 Sep  8 12:44 ..
drwxrwxrwx 1 root   root      8 Sep  8 13:02 10.4F7494010800
drwxrwxrwx 1 root   root      8 Sep  8 13:02 81.592527000000
drwxr-xr-x 1 root   root      8 Sep  8 13:02 alarm
drwxr-xr-x 1 root   root      8 Sep  8 13:02 bus.0
drwxr-xr-x 1 root   root      8 Sep  8 13:02 settings
drwxrwxrwx 1 root   root      8 Sep  8 13:02 simultaneous
drwxr-xr-x 1 root   root      8 Sep  8 13:02 statistics
drwxr-xr-x 1 root   root     32 Sep  8 13:02 structure
drwxr-xr-x 1 root   root      8 Sep  8 13:02 system
drwxr-xr-x 1 root   root      8 Sep  8 13:02 uncached

To read out the temperature from the DS18S20 IC we have to take a look at the file called temperature:

$ ls -la /home/thomas/owfs/10.4F7494010800
total 0
drwxrwxrwx 1 root root   8 Sep  8 13:03 .
drwxr-xr-x 1 root root   8 Sep  8 13:02 ..
-r--r--r-- 1 root root  16 Sep  8 13:02 address
-rw-rw-rw- 1 root root 256 Sep  8 13:02 alias
-r--r--r-- 1 root root   2 Sep  8 13:02 crc8
drwxrwxrwx 1 root root   8 Sep  8 13:03 errata
-r--r--r-- 1 root root   2 Sep  8 13:02 family
-r--r--r-- 1 root root  12 Sep  8 13:02 id
-r--r--r-- 1 root root  16 Sep  8 13:02 locator
-r--r--r-- 1 root root   1 Sep  8 13:03 power
-r--r--r-- 1 root root  16 Sep  8 13:02 r_address
-r--r--r-- 1 root root  12 Sep  8 13:02 r_id
-r--r--r-- 1 root root  16 Sep  8 13:02 r_locator
-r--r--r-- 1 root root  12 Sep  8 13:02 temperature
-rw-rw-rw- 1 root root  12 Sep  8 13:03 temphigh
-rw-rw-rw- 1 root root  12 Sep  8 13:03 templow
-r--r--r-- 1 root root  32 Sep  8 13:02 type

All data from the 1-Wire IC are contained in different files in OWFS, and the content of files can be displayed with the cat command in Linux:

$ cat /home/thomas/owfs/10.4F7494010800/temperature
24

So this value shows that the system is running and temperature measurements are being done (24 deg. C). Information about the type of IC is contained in the type file:

$ cat /home/thomas/owfs/10.4F7494010800/type
DS18S20

Just to proved that the resolution is higher than 1 deg. C I did one more readout and that showed 4 more digits after the previous value:

$ cat /home/thomas/owfs/10.4F7494010800/temperature
24.0625

The obvious next step is to build even more software on top of NSLU2 OWFS installation to make nice graphs over time to gain comprehensive information about the temperature.

The DS18S20 can of course be placed in many different locations, even outdoors if you use heat shrink to protect the IC against the weather.

(Update: Do your OWFS sensors disappear from time to time? Please join the discussion below).

Debian on NSLU2 With USB Hard Disk and Homeplug Network

This is an update on my NSLU2 1-Wire project. I wanted to use a wired Ethernet to WLAN adapter to connect the NSLU2 to the rest of the world, but I couldn’t make it work right away so I decided to use a power line Ethernet adapter instead of digging further into the problem. The system diagram now looks like this:

This is the way the system looks at the moment and I’ll start working on adding the 1-Wire components in the coming days. Here’s a link to the original diagram: NSLU2 1-Wire thermometer system

The power line Ethernet adapter, also called Homeplug, is one I bought from ZyXEL, model PLA-401 v3. There are only 2 connections, mains and Ethernet, so it’s really easy to use. You’ll need two units, one in each end of your power line network:

Here’s a picture of the system built according to the above diagram, with a 30 GB Quantum Fireball hard disk connected via USB:

And what better place to hide it than inside my home aquaponics system?:

Charlotte insisted that the aquaponics system had to be covered with white sheets, now that it has been set up in the corner of the living room, and it actually turned out to be a quite neat looking setup:

… just imagine how much electronics I could fit in there  – mmm… ;-)

The NSLU2 system is now close to the outer wall so I should be easy to get the 1-Wire cable outside to be able to measure outside temperature, both air and soil. And why not add a soil moisture sensor while we’re at it, or perhaps a rain sensor? Being right underneath the aquaponics system should make it easy to measure water temperature and pH too. The good thing about 1-Wire is that you can have many different IC’s connected to the bus at the same time on different addresses.

Getting the NSLU2 up and running with Debian is alway a bit challenging, at least for me, so here’s a brief description for reference:

  1. Google ‘nslu2 debian’ to get to the current installation instructions. I found them at www.cyrius.com/debian/nslu2/install.html
  2. Install upslug2 on Ubuntu laptop: sudo apt-get install upslug2
  3. Download software from www.slug-firmware.net/d-dls.php
  4. Unpack debian-armel-5.0.4.zip to di-nslu2.bin (8.0 MB)
  5. Power off NSLU2 and disconnect USB hard disk
  6. Put NSLU2 into upgrade mode
  7. Check that NSLU2 can be reached on the intranet: sudo upslug2
  8. Install Debian installer on NSLU2: sudo upslug2 -i di-nslu2.bin
  9. Power off NSLU2 and connect USB hub and hard disk
  10. Find IP address of NSLU2 on the intranet: nmap -sP 192.168.1.1-254
  11. Start Debian installer on NSLU2: ssh installer@192.168.1.27, password install
  12. Go to shell inside installer and set up name server: nano /etc/resolv.conf (DON’T reboot afterwards)
  13. Follow the instructions by the Debian installer for the next 4 hours… 8-|

Tip: If you can’t connect to the NSLU2 try removing the known hosts file on your laptop: rm .ssh/known_hosts

Now it’s time to add some 1-Wire components and install more software on the NSLU2 to be able to communicate with the 1-Wire IC’s.

Automatic Temperature Measurements Using NSLU2

The NSLU2 is a small computer, that was sold as a NAS device by Linksys. NAS stands for Network-Attached Storage which means that you can connect a hard disk to your network, hence the name Network Storage Link for USB 2.0 Disk Drives.

It was discontinued in 2008, but I still have three old units that I have used for different purposes in the past. One of them was used in a 1-Wire thermometer system like this:

The good thing about the NSLU2 is the low power consumption, around 5 watts, which means that you can leave the unit on 24/7 without it showing up on your electrical bill.

The above diagram is actually showing the new system I’m going to build, because in my previous system the external storage device was a 2 GB USB stick which meant that the power consumption was even lower compared to a 3.5″ hard disk. I’ll go with the hard drive this time to get more storage capacity and hopefully better stability. I don’t know if this will provide more stability but I’ve had problems with data loss on my previous systems and I know you’re supposed to make some software tweaks on the NSLU2 if you use USB storage with flash memory because of the frequent data write operations. I did make the tweaks though, but time will tell if system crashing is related to flash memory. As operating system on the NSLU2 I use Debian.

The NSLU2 measures 131 x 96 x 28 mm and has 2 USB ports and 1 Ethernet port. The processor inside is a 266 MHz ARM Intel XScale IXP420 with access to 32 MB SDRAM and 8 MB flash memory:

Conversion between USB and 1-Wire can be done with a DS9490 adapter available from Hobby-Boards.com:

The 1-Wire network is connected to a RJ12 telephone connector which means only 6 pins compared to the 8 pins in a standard Ethernet connector.

Somewhere in the 1-Wire network you can connect one of these small 3 pin IC’s for temperature measurements:

This one looks like a transistor but it’s actually a DS1820 1-Wire IC. The power is supplied through the 1-Wire cable. I just use normal Ethernet cable as 1-Wire cable.

If the NSLU2 is placed far away from your Ethernet network you can use a Ethernet to WLAN converter. The WL-330gE from ASUS is even powered by USB:

It is possible to have a long 1-Wire network cable, a long Ethernet cable, or a long mains cable, when you need to connect the system to the rest of the world, which should make it easy to set up the system almost anywhere you want.

This is my old external USB hard disk that I plan on using for storage:

and a small handy two port USB hub, powered by the USB port itself:

I really like the NSLU2 as it gives you a lot of possibilities to make all kinds of fun stuff, but I also realize that it’s getting more difficult to get hold of a functioning unit ever since it was discontinued. If you haven’t got a unit already you should take a look at the SheevaPlug plug computer, or the Arduino project.

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