Hacking the TomTom ONE through Open Source

David M Williams
Monday, 16 July 2007 09:18

Business IT - Open Source

It's not been quite that simple; for starters, the device doesn't have a keyboard or hard drive and nor can it be made to boot from a USB drive. Original work to reign in the GO centered around attempts to invoke a remote shell login while USB-connected to a computer. Some not insignificant success was achieved when it was fdiscovered that the system's start-up scripts contained a call to a file called /mnt/sdcard/ttn - i.e. an executable program called ttn located on the SD card. This meant it became trivial to have the TomTom run any custom app provided it was named ttn and saved to the memory stick.

Unfortunately, the TomTom didn't cater for pseudo-terminals - the /dev/pty devices that represent remote logins, as opposed to the /dev/tty devices which correspond to physical keyboards (or TeleTYpes). Thus, remote login still appeared unassailable until finally a TCP/IP stack was brought to heel under Bluetooth via the rfcomm utility. This finally permitted remote command-line sessions from a desktop computer. Even so, little could be performed except to probe the innards of the system.

In an unexpected twist of events, the gpl-violations.org project took exception to TomTom building an embedded Linux system without going along with the GNU General Public License (GPL) constraints that the Linux kernel used, and custom modifications, be freely available as open source. They were successful in this and TomTom agreed to release the full source code including all additions and changes made in-house. Additionally, TomTom showed their "appreciation" for Free Software by making a donation, described as "significant", to the infamous Chaos Computer Club - read into this what you may.

The result was a breakthrough and brought forth a cornucopia of technical information. The SatNav vendor now provides free downloads for all versions of its GO software from version 4 to the present 6.5. Additionally, TomTom detail the compilers and libraries they used to build the embedded OS and provide both Linux and Windows versions of the necessary toolchain that targets the ARM processor. It is actually surprising how many open source elements are used including terminal emulators, tools to erase flash memory and tools to initialise Bluetooth, the popular MPlayer multimedia player and others and thus gpl-violations.org were right to pursue the matter.

It must be clearly pointed out that the TomTom mapping and navigation application itself remained fully proprietary; it was the GO's operating system which was the subject of the violation. This was fine; for the wiley hackers, the actual SatNav software - despite being the primary focus for general consumers - was totally irrelevant. The goal was to master the box itself.