jidhage.se

personal thoughts and projects in security

Übertooth

Intro

During the spring 2011 I stumbled upon Michael Ossmann’s  presentation from ShmooCon regarding the open source hardware bluetooth dongle he developed and i got really inspired. I wanted one of those! At that moment Micheal had just started a Kickstarter project but the delivery was a couple of weeks away and I saw this as an opportunity to get back into electronics and soldering and at the same time get acquainted with SMB – I didn’t even know it was possible to perform SMB soldering at home. So I went for doing it all by my self.

Another one of my decision that wasn’t all that clever…

Phase 1 – initial energy

Reading the instructions and following them step by step on the Ubertooth site, the first action was to order the circuit board. I chose Laen as supplier and two weeks later the Ubertooth boards arrived together with PogoProg – the official firmware installer hardware, basically a USB to serial converter. Total cost so far $26.30USD

Phase 2 – getting embarrassing

Cleaning PogoProgs before applying solder paste

Time passed and nothing happened, when we reached Christmas it was getting embarrassing, especially since you could get your hands on an assembled Ubertooth from several web shops by now, it was time to act – a community hack was arranged by the local OWASP Chapter in February and my plan was to be ready by then to assemble the boards.

January 29th – I ordered two solder masks from Pololu after comparing the cost and services of some suppliers, both locally and abroad. One mask was for the Pogoprog and one for the Ubertooth board. Cost $75.95 USD
January 31st – I ordered components from Mouser, I was initially looking to order from a local supplier but manually going through the BoM and finding replacements for every single part was just too much hard work. Mouser had some BoM and ‘project’ support and finding replacements for the few components that wasn’t an immediate match was a breeze – I would say that the hardest part was to compile a single BoM for the joint PogoProg + Ubertooth + spares order. I actually failed at ordering any flexible probes for the PogoProg and I still haven’t gotten around to do it – if anyone can recommend a good supplier&part – I’m all ears. Cost 1.194,39 SEK

CommunityHack-day was getting close and a friend of mine supplied a soldering iron and hot air rework station – all the parts arrived as planned and I was ready for some serious SMB assembly.

I was aiming for cooking the circuit with the instructions found here and aiming to follow the tutorial on Solder Paste Stenciling on the same site (www.SparkFun.com). The day before I went on a shopping spree to buy rubbing alcohol and an extra pair of tweezers. I felt as prepared as I would ever be.

Phase 3 – the hack

Thanks to the girlfriend for lending me a pair of tweezers. PogoProg is pretty easy assembly compared to the Ubertooth

We worked hard for 10 hours straight with one short break for pizza. Aiming for the PogoProgs first was a great move, a small board with reasonable amount of components and very few 0402-sized. Getting used to stenciling and components placements and then reflowing on the pan. A great start to the day.

Ok, that was easy – let’s go all in and produce some Ubertooth boards! Just a few minutes into the components placements we realized reflowing with a frying pan was not the hard part, as I initially thought. Applying the correct amount of solder with the mask was much harder and placing the components, especially the 0402’s – was a nightmare. The hands wasn’t steady enough. There was either too much or too little solder paste. And trying to adjust the position if your first attempt wasn’t 100% succesful – all in all, one of the most demanding miniscule tasks I’ve ever considered…

We found ourselves laughing nervously from time to time – the situation was absurd – trying to place little grains of sands (0402) with correct alignment on a matchbox-size board, and then we were going to cook it on a plate – not on your every day todo list. But I admit is was great fun!

And even though the result wasn’t a 100% when we had to close down since the event came to an end, a feeling of accomplishment came over me during the final session at the frying pan.

Current status

After the CommunityHack the boards were safely tucked away in my bag for about three months as life and work got in the way…
When I finally got the energy to unpack I performed an ocular inspection and immediately fixed some minor soldering errors on the PogoProg’s and performed an initial power-on test – and presto! The TX and RX LEDs flashed as they supposed to. We have three working PogoProgs!

The case for the Ubertooth boards are not all that promising; one is fully functional, one passes the test protocol but refuses to accept any firmware updates after the first programming. The third is physically broken – need to give this one a lot of love for a happy ending…

Plans

Cooking up some bluetooth goodness

I’m aiming for scheduling a weekend for some serious work on the boards. With some luck we will have three fully functional boards just around the time when we need to focus on the next project from Mr Ossmann: HackRF

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