The whitestar project is my attempt at building a reliable and fully automatic wardriving equipment for permanent installation in my car. It's used to constantly gather 802.11 data for research purposes and contribution to the https://wigle.net crowdsourced WLAN map.

This may not be the most recent project information page. I have copied this information from my private site: http://pop.fsck.pl/projects/whitestar/ and it's a good idea to check there for updates. I will try to post them here as well but without some automated system that I'm yet to build there can be a delay ;).

1 The hardware

The whitestar is built around a kektop (NTT HOME W 300P net-top style PC) with an Intel Atom 230 CPU (1.6 GHz), 1 GB of RAM and a small 16GB internal SSD. The kektop has two wireless cards and a GPS connected via USB for wardriving purposes. There is also an ELM327 interface connecting to the car OBD-II port. Additionally, I figured I should store all of the data outside of the internal SSD to increase its life expectancy. For this purpose I connected a 2.5'' 500 GB USB hard disk. A laptop HDD was chosen because of better vibration resistance making it possible for it to actually survive working in a car for extended periods of time.

2 Power

In the beginning the whitestar was powered directly from the car lighter socket via a step-up converter from Aliexpress (XL6009-based). One of the improvements I wanted to make after using it for a while was to add some basic UPS capability to it. This is because the cigarette lighter power source has some drawbacks in a car. There are some situations where the voltage there drops causing the computer to reboot loosing packet capture ability for the amount of time it takes to boot up again. Also, short stops in your trip (for example gas stations) should not cause the packet capture to stop and restart.

So there are two problems here. The first one is a momentary drop in voltage as the engine is started (which reboots the kektop). The second problem are short stops (think gas station) where it would be nice to keep the kektop running for a few minutes. To solve both of those I acquired a suitable battery. In the spirit of efficiency I simply purchased a powerbank with a 19 V laptop output that can supply enough power to run the whitestar for a few minutes. You would find it hard to be more generic than this brand:

During some initial attempts at connecting all of this together I figured out that I can't just plug the powerbank to car 12 V to keep it constantly charging and power the whitestar from it's 19 V output. This is because the charger built into the powerbank will not be able to keep up and keep the Li-ION battery charged. A different approach is therefore needed, where a relay will switch the load from car 12V to the battery and vice versa. To keep the kektop running during this time I figured I would need a supercap bank. Therefore I bought and built it:

The resulting capacitor bank has 10F@27V (10 x 10F@2.7V). It can power the kektop for a good few seconds. So I decided to build a first version of the UPS to test it out, without the battery and relays first. Just the supercaps so that I would see will the kektop survive an engine start without a reboot.

For now the connections are:

Cat 12V input <-> 10F@27V supercaps <-> SMPS <-> 19V <-> kektop

2 Software setup

The software that I used was based on a clean Xubuntu installation with a GUI. After that I added some packages and changed some configuration options.

All of the scripts mentioned are available on github: https://github.com/mgrela/whitestar

Below is a step-by-step guide for installing everything:

2.1 BIOS setup

First we need to enter the BIOS of the machine and set up two important options:

• enable automatic poweron on AC failure
• disable all other booting mechanisms except internal HDD

2.2 OS installation

The OS installed on the device is Xubuntu 15.10:

$ lsb_release -a
No LSB...