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June 30, 1999

The Linux-powered telephone

There are many who will say that Linux is not sufficiently friendly to be installed on your parents' computer. So how would you feel about putting it on their telephone? [Touchphone] That is exactly what the Italian firm Sorgenti has done - created a Linux-powered telephone. It is an interesting device that shows how Linux can be part of a successful consumer product; it may prove to be just one of the first in a long series of Linux deployments in consumer devices.

The Touchphone is a certainly a gorgeous piece of Italian styling. Some information on its features can be found at its web site - touchphone.com - which is rather highly styled in its own right. The appearance of the telephone is dominated by an LCD display and touchscreen, which makes up the entire interface. Using the touchscreen, it is possible to store and recall phone numbers, edit, send and receive faxes and electronic mail, and to store miscellaneous notes. There is an answering machine built in. Oh, and you can make phone calls as well.

The creation of the Touchphone

While Sorgenti is the producer of the phone, when the time came to actually make something work they went to Prisma Engineering srl. Prisma is a Milan-based engineering firm; their 25 software engineers work mostly in the areas of telecommunications and embedded systems applications. Linux is a familiar beast to them - they have used it in projects with some of their telecom projects; it is also running on their Internet gateway. They see a day, not too far away, when Linux might start appearing as part of the operational wireless telecom networks.

One day, Prisma was approached by Sorgenti and asked if they could design and build an embedded system to operate an intellegent telephone. It had to provide all of the features described above, cheaply. The hardware inside the device had to be cheap: a 386 processor, 4MB of memory (since bumped up to 8), a small disk, and a touchscreen driven by a VGA controller. Who could resist a challenge like that?

Prisma did its research, but, in the end, the choice was obvious. The Touchphone would run Linux.

Underneath it all, the Touchphone is running a modified, much reduced version of Red Hat 4.2. The fax and answering machine code is all derived from open source systems (efax and vgetty) with just a few modifications for the embedded environment. The graphics are done with SVGAlib, which required a fair amount of work to produce the performance required in the system. There is no keyboard, of course, just the touchscreen over the LCD panel, which is attached to the system via a serial port. [Notes editor]

Prisma wrote a graphical editor which handles notes and fax editing. It is, as they say, "fun" to draw on an eight-inch touchscreen with your fingers.

The rest of the system, interestingly enough, is done with simple shell scripts which are invoked in response to touchscreen events. One does not ordinarily think of shell scripts as the development environment for this sort of device. But life is easier when you have Linux running underneath you.

The end result is a nice piece of consumer electronics. Users of Touchphones have no idea that they are using Linux - they think they are using a telephone.

Does it work?

How well does this all work? Many thousands of these telephones have been sold since last October. Thus far, exactly one of them has come back with a corrupted filesystem. Think about the operating environment of a typical Touchphone for a moment: it lives in the kitchen, next to the espresso machine. The children play with it. It is running 100% of the time. Nobody thinks about shutting it down gracefully before unplugging it (probably because there is only one outlet and they need their coffee). That these phones can work so reliably in those conditions testifies not only to the robustness of the Linux operating system, but also to a great deal of care taken by the people at Prisma Engineering.

The Touchphone is upgradable as well. The process, which uses the user's Internet connection, is entirely automatic. A set of shell and Expect scripts makes the whole thing happen.

A couple of future enhancements are in the works. At the low end, a diskless version will be offered at a lower price. Another variant will include a web browser along with all the other features.

One aspect of "how it works" that is not yet clear: Sorgenti did not respond to a question as to whether they make available the source for the GPL software in their product. They are, of course, required to do so by the terms of the license. In any case, the most interesting software in the device is in the form of separate, add-on programs which work in a specialized environment. This software is not covered by the GPL, and is probably not very useful to others.

Linux and embedded systems

It has often been claimed that computers will eventually disappear from sight, much in the way of electric motors. The Touchphone shows what that future might look like - and Linux could well be a big part of it. There are numerous reasons for Linux to prosper in this environment - and they are mostly the same reasons for the success of Linux in other areas:
  • Cost. A consumer device like the Touchphone must be inexpensive - there are limits to what people want to spend on a telephone. Software licensing fees make a big difference in this realm.

  • Reliability. Embedded systems simply can not crash.

  • Resource utilization. Embedded systems generally have to be small and cheap. Whatever operating system runs on them must be able to make good use of low-power hardware.

  • Source availability. Every embedded application will be different, and will require the ability to customize the system to the environment. In addition, as Prisma engineer Paolo Marini told me, "In my experience, when the source for the system software is not available, small problems require excessive amounts of time and effort to resolve." Source is power.
Linux looks like a real winner in the embedded environment. It nicely satisfies the requirements of such applications, while simultaneously providing a great deal of power to developers. Watch this space: as computers disappear, Linux will be hiding in there with them.


The Touchphone was developed by:
  • Sergio Troni - touchscreen and hardware management,
  • Pietro Bertozzi - User interface and system software,
  • Paolo Marini - System software and fax, modem, and email management,
  • Paolo Baccalaro - Design and graphics
I would like to thank Paolo Marini for providing so much information that this article almost entirely wrote itself. Any errors in translation from Italian are entirely the author's fault.

-- J. Corbet.

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