I love this article on zdnet from David Greenfield. It’s a round-up of what’s happening in the up and coming area of Open Source Hardware. According to David,

A burgeoning trend in open source hardware is putting up some devices on the Web — from machines that make anything (including themselves) to cars — with the specs to make them yourself (See our list below). While still in its infancy, the trend could redefine hardware cost models much as its done for software.

And there are some neat really ideas like this one which I have been following myself for a while:

Now that you’ve got Asterisk, what hardware platform will you run the software on? Usually folk settle on a Intel or AMD based-server of one kind or another. You can build your own PBX hardware with the Astfin Project or buy one for just $450 from the Free Telephony Project store.

This Asterisk appliance project has the chap who wrote the brilliant Open Source Echo Canceller I mentioned before in it.

But how about your own, Open Source Car…

Open Source isn’t just for your office. The OScar aims to be the first open source automobile. The goal is to create a utilitarian car that aims to move people from place-to-place sans a lot of the high-tech gadgetry that runs in today cards. Initial concepts call for a four-door, four meter length vehicle weighing about 1000 Kilo capable of reaching 145 KM/hour.

Cool - just the thing to keep a man happy and content in his shed for months.

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O.K. I said I’d write a bit about an excellent new echo canceller which happens to work with Asterisk. Here it is it’s called OSLEC the Open Source Line Echo Canceller and it’s written by a chap called David Rowe.

As readers may recall, I’ve built a small home server (VIA CN700) on which I plan to run Asterisk, Samba and Untangle. Samba is up and running and Asterisk is too. I have a single port, very cheap (about £15 inc postage from the USA) x100p card providing an interface to a normal analogue PSTN telephone line.

When we got everything working, we noticed a great deal of echo on voice calls over the x100p. Lots of playing with gains and various settings in the zaptel configuration failed to make any noticeable difference.

I came across this site whilst looking for something completely different and started to read… It sounded like just the thing. A bit of jiggery and a quick patch to the zaptel-1.4.5.1 sources - thanks to the asterisk mailing list - and I got the OSLEC canceller working.

Basically here’s what to do:

1. Build the OSLEC module (it will need to find your kernel sources - just like zaptel) according to the instructions on the website. Once built and you’ve checked that you can install it by inserting the module into your running kernel, copy it (oslec.ko) to your kernel’s loadable module directory: on my system the zaptel modules reside in /lib/modules/2.6.23/misc/ so that’s where I put the oslec module too.
2. Patch your zaptel source tree (if you have version 1.4.5.1 you will need to patch Makefile.kernel26 or OSLEC will never get loaded) and rebuild and re-install as described. (Caution: Backup your /etc/zaptel.conf, /etc/asterisk/zapata.conf and your modified SysV init scripts so you can simply overwrite the default files installed when you rerun make install on the zaptel sources.)
3. Edit your zapata.conf so the following are as below:echocancel=yes
echocancelwhenbridged=no
;echotraining=400
4. Reload everything (if in doubt, stop asterisk and zaptel using your SysV init scripts, e.g # /etc/rc.d/init.d/{asterisk,zaptel} stop. Then start them again. When zaptel starts you should see a message saying Echo canceller OSLEC or something like that; if it says MG2 then it isn’t working so you need to go back and recheck your build and patching and module loading.

That’s it.

Now make or receive a call through your cheap x100p card and marvel at the clear echo free sound! It worked brilliantly for me. Of course YMMV but it is definitely worth a try. Most of the reports on the ‘net are incredibly positive about this.

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There’s no Untangle in this instalment - I’m awaiting a new kernel from the developers before I can get any further; it should be here shortly however.

In the previous article of this series I mentioned that I’d explain how to get Asterisk built and running as a non-root user. It wasn’t too hard to be honest but I’ll document it anyway.

The problem: Asterisk by default, when compiled from source, expects to be run as root. For userspace applications, this is NEVER a good idea in my opinion. After all we’re running on a multi user system that can support non-root processes - unlike Windows - so we really should…

The solution for Asterisk-1.4.13 on my LFS based system, is as follows:

Build any hardware add-ons and codecs you need before building Asterisk. I built the Zaptel module for my x100p card and the Speex Open Source VBR codec. The zaptel module needs to find your kernel source tree (usually in /usr/src/linux-2.6.x.x). To build the zaptel source:

./configure --prefix=/usr
make menuselect (to select/deselect the modules you wish to build)
make

then as root:

make install

and optionally:

make config This will install the SysV init scripts and some default configuration files. You may need to modify the init scripts depending on your system.

Simply follow a similar process for the Speex codec…

For Asterisk, start off by creating a group and user that will run and own the asterisk process and files (select {G,U}IDs and names that are appropriate for your system).

groupadd -g 75 asterisk
useradd -c "Asterisk PBX" -d /var/lib/asterisk -g asterisk -s /bin/false -u 75 asterisk

Edit the Makefile in the top of the asterisk source tree so that the line:

ASTVARRUNDIR=${localstatedir}/run becomes ASTVARRUNDIR=${localstatedir}/run/asterisk

Then build as normal

./configure --prefix=/usr
make menuselect (Turn on/off various modules and options. Select sound files/language/format and extra sounds. Type “s” to save and exit)
make

Then as root:

make install

Asterisk is now installed. But because we will run the process as non-root it needs write permissions for these directories and their contents:

/var/lib/asterisk, /var/log/asterisk, /var/run/asterisk, /var/spool/asterisk, /dev/zap/*.

If you installed the zaptel modules and used the ‘make config’ command, a udev rules file (zaptel.rules) will be written to /etc/udev/rules.d. This enables, by default, udev to create the zaptel device files as user:group asterisk. If you chose another name above you will need to edit this file accordingly.

O.K., lets sort out the ownership and access to the files Asterisk needs. First change the owner:

chown -R asterisk:asterisk /var/{lib/asterisk,log/asterisk,run/asterisk,spool/asterisk}

Now set read/write only by owner, read only by group and no access by other:

chmod 750 /var/{lib/asterisk,log/asterisk,run/asterisk,spool/asterisk}
chmod -R o= /var/{lib/asterisk,log/asterisk,run/asterisk,spool/asterisk}

This switch (chmod -R o=) is pretty cool by the way. It removes all access to all files and directories for the “other” classification, effectively setting them to “0″ but does not change or overwrite any of the permissions for owner and/or group access.

The asterisk process itself only needs read permission for the configuration directory (/etc/asterisk) and its contents:

chown -R root:asterisk /etc/asterisk
chmod 750 /etc/asterisk
chmod 640 /etc/asterisk/*

Some of Asterisk’s ‘.conf’ files contain cleartext passwords and other potentially sensitive information. Setting the files as above permits read/write only by the user root and read only by members of the group asterisk.

That’s it basically. When you start asterisk from the SysV init scripts, pass the following arguments to have it run, safely, as your new user:

asterisk ${DEBUG} ${ZAP_TIMING} -U ${USER} -G ${GROUP}

In my startup script, I’ve set those constants above to be:
# If you want debug messages to the console and the logs switch the
# comments below
DEBUG=""
#DEBUG="-d"
# The user and group we created earlier
GROUP="asterisk"
USER="asterisk"
# Use this if you want to limit the maximum number of simultaneous calls
# to prevent system failure for example
MAXCALLS=""
#MAXCALLS="-m 20"
# If you have a Zaptel card/timing source, enable it here
#ZAP_TIMING=""
ZAP_TIMING="-I"

That’s it.

When asterisk starts, it will run as the user and group defined above. In the next instalment, I will write a bit about a fantastic new echo canceller which sorts out cheap x100p cards and makes them work properly… It’s really excellent.

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