Decoding Satellite-based Text Messages with RTL-SDR and Hacked GPS Antenna

[Carl] just found a yet another use for the RTL-SDR. He’s been decoding Inmarsat STD-C EGC messages with it. Inmarsat is a British satellite telecommunications company. They provide communications all over the world to places that do not have a reliable terrestrial communications network. STD-C is a text message communications channel used mostly by maritime operators. This channel contains Enhanced Group Call (EGC) messages which include information such as search and rescue, coast guard, weather, and more.

Not much equipment is required for this, just the RTL-SDR dongle, an antenna, a computer, and the cables to hook them all up together. Once all of the gear was collected, [Carl] used an Android app called Satellite AR to locate his nearest Inmarsat satellite. Since these satellites are geostationary, he won’t have to move his antenna once it’s pointed in the right direction.

Hacked GPS antenna
Hacked GPS antenna

As far as antennas go, [Carl] recommends a dish or helix antenna. If you don’t want to fork over the money for something that fancy, he also explains how you can modify a $10 GPS antenna to work for this purpose. He admits that it’s not the best antenna for this, but it will get the job done. A typical GPS antenna will be tuned for 1575 MHz and will contain a band pass filter that prevents the antenna from picking up signals 1-2MHz away from that frequency.

To remove the filter, the plastic case must first be removed. Then a metal reflector needs to be removed from the bottom of the antenna using a soldering iron. The actual antenna circuit is hiding under the reflector. The filter is typically the largest component on the board. After desoldering, the IN and OUT pads are bridged together. The whole thing can then be put back together for use with this project.

Once everything was hooked up and the antenna was pointed in the right place, the audio output from the dongle was piped into the SDR# tuner software. After tuning to the correct frequency and setting all of the audio parameters, the audio was then decoded with another program called tdma-demo.exe. If everything is tuned just right, the software will be able to decode the audio signal and it will start to display messages. [Carl] posted some interesting examples including a couple of pirate warnings.

If you can’t get enough RTL-SDR hacks, be sure to check out some of the others we’ve featured in the past. And don’t forget to send in links to your own hacking!

Hackaday Prize Entry: Project Dekoboko 凸凹 Maps Bumpy Roads On A Bike

If you live in New England (like me) you know that the roads take a pounding in the winter. Combine this with haphazard maintenance and you get a recipe for biking disaster: bumpy, potholed roads that can send you flying over the handlebars. Project Dekoboko 凸凹 aims to help a little with this, by helping you map and avoid the bumpiest roads and could be a godsend in this area.

The 2015 Hackaday Prize entry from [Benjamin Shih], [Daniel Rojas], and [Maxim Lapis] is a device that clips onto your bike and maps how bumpy the ride is as you pedal around. It does this by measuring the vibration of the bike frame with an accelerometer. Combine this with a GPS log and you get a map of the quality of the roads that helps you plan a smooth ride, or which could help the city figure out which roads need fixing the most.

bike-measures-bumpy-roads-thumbThe project is currently on its  third version, built around an Arduino, Adafruit Ultimate GPS Logger shield, and a protoboard that holds the accelerometer (an Analog ADXL345). The team has also set up a first version of their web site, which contains live data from a few trips around Berlin. This does show one of the issues they will need to figure out, though: the GPS data has them widely veering off the road, which means that the data was slightly off, or they were cycling through buildings on the Prinzenstrasse, including a house music club. I’ll assume that it was the GPS being inaccurate and not them stopping for a rave, but they will need to figure out ways to tie this data down to a specific street before they can start really analyzing it. Google Maps does offer a way to do this, but it is not always accurate, especially on city streets. Still, the project has made good progress and could be useful for those who are looking for a smooth ride around town.

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Hackaday Prize Entry: A Tiny Tool for Car Hacking

A car from 1940 would have been an almost completely mechanical device. These days though, a car without electricity wouldn’t run. It’s not the engine – it’s the computers; the design details of which automotive manufacturers would love to keep out of the hands of hardware hackers like us. [Mastro Gippo] wanted to build a small and powerful CAN bus reverse engineering tool, and the Crunchtrack hits it out of the park. It’s a CAN bus transceiver, GPS receiver, and GSM modem all wrapped up into a single tiny device that fits under your dash.

[Mastro] has a slight fetish for efficiency and tiny, tiny devices, so he’s packaging everything inside the shell of a standard ELM327 Bluetooth adapter. This is a device that can fit in the palm of your hand, but still taps a CAN bus (with the help of a computer), receives GPS, and sends that data out over cell phone towers.

The device is based on the STM32 F3 ARM microcontroller (with mbed support), a ublox 7 GPS module, and an SIM800 GSM module, but the story doesn’t stop with hardware. [Mastro] is also working on a website where reverse engineering data can be shared between car hackers. That makes this an excellent Hackaday Prize entry, and we can’t wait to see where it goes from here.

The 2015 Hackaday Prize is sponsored by:

Hackaday Prize Entry: 20,000 Weather Stations

Team Tahmo has a plan to put a network of 20,000 weather stations across sub-Saharan Africa. That’s an impressive goal, and already they have pilot stations in Senegal, Chad, Nigeria, Uganda, and South Africa. For their Hackaday Prize entry, they thought it would make sense to add more advanced sensors to their weather stations, and came up with GPS, lightning, and large scale soil moisture sensors.

The sensors already deployed have the usual complement of meteorological equipment – thermometers, anemometers, barometers, and rain gauges. These stations are connected to a school’s Internet connection where students can monitor the local weather patterns and upload the data. Team Tahmo is building a small add-on board for their Prize entry using an AS3935 Franklin Lightning sensor and a GPS module.

In the interests of rapid design cycles, the team is using off-the-shelf modules for the lightning detector and GPS module. They hit up the Hackaday Prize Collabratorium for some advice on PCB design and have everything pretty much nailed down thanks to a few helpful hackers.

It’s a great project for one of the most ambitious crowdsourced data gathering projects ever conceived, and something that would vastly improve weather predictions across the African continent. Even if their entry does just monitor lightning strikes, it’s still an admirable goal and one of the most useful projects for this year’s Hackaday Prize.

The 2015 Hackaday Prize is sponsored by:

Punky GPS Gets The Steam Built Up For Geocaching

While getting geared up for geocaching [Folkert van Heusden] decided he didn’t want to get one of those run of the mill GPS modules, and being inspired by steam punk set out and made his own.

Starting with an antique wooden box, and adding an Arduino, GPS module, and LiPo battery to make the brains. The user interface consists of good ‘ole toggle switches and a pair of quad seven segment displays to enter, and check longitude and latitude.

To top off the retro vibe of the machine two analog current meters were repurposed to indicate not only direction, but also distance, which we think is pretty spiffy. Everything was placed in a laser cut wooden control panel, which lend to the old-time feel of the entire project.

Quite a bit of wire and a few sticks of hot glue later and [Folkert] is off and ready for an adventure!

Castrol Virtual Drift: Hacking Code at 80MPH with a Driver in a VR Helmet

Driving a brand new 670 horsepower Roucsh stage 3 Mustang while wearing virtual reality goggles. Sounds nuts right? That’s exactly what Castrol Oil’s advertising agency came up with though. They didn’t want to just make a commercial though – they wanted to do the real thing. Enter [Adam and Glenn], the engineers who were tasked with getting data from the car into a high end gaming PC. The computer was running a custom simulation under the Unreal Engine. El Toro field provided a vast expanse of empty tarmac to drive the car without worry of hitting any real world obstacles.

The Oculus Rift was never designed to be operated inside a moving vehicle, so it presented a unique challenge for [Adam and Glenn]. Every time the car turned or spun, the Oculus’ on-board Inertial Measurement Unit (IMU) would think driver [Matt Powers] was turning his head. At one point [Matt] was trying to drive while the game engine had him sitting in the passenger seat turned sideways. The solution was to install a 9 degree of freedom IMU in the car, then subtract the movements of that IMU from the one in the Rift.

GPS data came from a Real Time Kinematic (RTK) GPS unit. Unfortunately, the GPS had a 5Hz update rate – not nearly fast enough for a car moving close to 100 MPH. The GPS was relegated to aligning the virtual and real worlds at the start of the simulation. The rest of the data came from the IMUs and the car’s own CAN bus. [Adam and Glenn] used an Arduino with a Microchip mcp2515 can bus interface  to read values such as steering angle, throttle position, brake pressure, and wheel spin. The data was then passed on to the Unreal engine. The Arduino code is up on Github, though the team had to sanitize some of Ford’s proprietary CAN message data to avoid a lawsuit. It’s worth noting that [Adam and Glenn] didn’t have any support from Ford on this, they just sniffed the CAN network to determine each message ID.

The final video has the Hollywood treatment. “In game” footage has been replaced with pre-rendered sequences, which look so good we’d think the whole thing was fake, that is if we didn’t know better.

Click past the break for the final commercial and some behind the scenes footage.

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New Part Day: Indoor Location Systems

GPS is an enabling technology that does far more than the designers ever dreamed. If you want a quadcopter to fly to a waypoint, GPS does that. If you want directions on your phone, GPS does that. No one in the 70s or 80s could have dreamed this would be possible.

GPS, however, doesn’t work too well indoors. This is a problem, because we really don’t know what is possible if we can track an object to within 10cm indoors. Now there’s a module that does just that. It’s the decaWave DWM1000.

This module uses an 802.15 radio to track objects to within just a few centimeters of precision. It does this by sending time stamps to and from a set of base stations, or ‘anchors’. The module is also a small, and relatively high bandwidth (110kbps) radio for sensors and Internet of Things things makes it a very interesting part.

Some of the potential for this module is obvious: inventory management, and finding the remote and/or car keys. Like a lot of new technology, the most interesting applications are the ones no one has thought of yet. There are undoubtedly a lot of applications of this tech; just about every ball used in sports is bigger than 10cm, and if ESPN ever wanted even more cool visuals, just put one inside.

If you’d like to try out this module, decaWave has an eval kit available through distributors for about $600. Somehow, there’s also a Kickstarter for a board that uses the same module, Arduino compatible, of course.

Thanks [Roy] for the tip.