Tapping Data From Radio-Controlled Bus Stop Displays 75
jones_supa writes "A couple of weeks ago hacker Oona Räisänen told about finding a 16 kbps data stream on FM broadcast frequencies, and her suspicion was that it's being used by the public transit display system in Helsinki, Finland. Now it's time to find out the truth. She had the opportunity to observe a display stuck in the middle of its bootup sequence, displaying a version string. This revealed that the system is called IBus and it's made by the Swedish company Axentia. Sure enough, their website talks about DARC and how it requires no return channel, making it possible to use battery-powered displays in remote areas. Other than that, there are no public specs for the proprietary protocol. So she implemented the five-layer DARC protocol stack in Perl and was left with a stream of fully error-corrected packets on top of Layer 5, separated into hundreds of subchannels. Some of these contained human-readable strings with names of terminal stations. They seemed like an easy starting point for reverse engineering..."
Re:See, this is kinda what I meant (Score:5, Insightful)
when I said you don't need an oscilloscope anymore. Probably a SDR receiver that goes to a PC.
At what stage in this project would an oscilloscope have been needed anyway? Yes, she used an SDR for scanning radio frequencies.
What possible interest is there in looking at the raw RF at the antenna, which you won't see with an oscilloscope anyways (because I don't know any scopes with nV/cm settings yet), or the countless undocumented signals inside the receiver, which you won't access anyways because it's all on one chip?
What is all on one chip? How is this rambling statement even applicable to this article?
It's all wonderful fun, but when you can do the same with a 15$ USB receiver and some software, it all starts to look rather silly, no?
You can decode these IBus messages with a $15 USB receiver? Link please?