Author: Mathieu Stephan

180 Articles

Introducing The F*Watch, A Fully Open Electronic Watch

October 17, 2014 by 24 Comments

As one of their colleagues was retiring, several CERN engineers got together after hours during 4 months to develop his gift: a fully open electronic watch. It is called the F*Watch and is packed with sensors: GPS, barometer, compass, accelerometer and light sensor. The microcontroller used is a 32-bit ARM Cortex-M3 SiLabs Giant Gecko which contains 128KB of RAM and 1MB of Flash. In the above picture you’ll notice a 1.28″ 128×128 pixels Sharp Memory LCD but the main board also contains a micro-USB connector for battery charging and connectivity, a micro-SD card slot, a buzzer and a vibration motor.

The watch is powered by a 500mA LiPo battery. All the tools that were used to build it are open source (FreeCAD, KiCad, GCC, openOCD, GDB) and our readers may make one by downloading all the source files located in their repository. After the break is embedded a video showing their adventure.

Continue reading “Introducing The F*Watch, A Fully Open Electronic Watch” →

Introducing USB Armory, A Flash Drive Sized Computer

October 14, 2014 by 22 Comments

[Andrea] tipped us about USB armory, a tiny embedded platform meant for security projects. It is based on the 800MHz ARM Cortex-A8 Freescale i.MX53 together with 512MB of DDR3 SDRAM, includes a microSD card slot, a 5-pin breakout header with GPIOs/UART, a customizable LED and is powered through USB.

This particular processor supports a few advanced security features such as secure boot and ARM TrustZone. The secure boot feature allow users to fuse verification keys that ensure only trusted firmware can be executed on the board, while the ARM TrustZone enforces domain separation between a “secure” and a “normal” world down to a memory and peripheral level. This enables many projects such as electronic wallets, authentication tokens and password managers.

The complete design is open hardware and all its files may be downloaded from the official GitHub repository. The target price for the final design of the first revision is around €100.

Mooltipass Installation Process Is Now Dead Simple

October 13, 2014 by 62 Comments

In a few weeks the Hackaday community offline password keeper will reach a crowdfunding platform. This is a necessary step as only a high production volume will allow our $80 early bird perk target. We’ll therefore need you to spread the word.

Thanks to the Chromium development team, a few days ago the Mooltipass installation process became as simple as installing our app & extension. As you may remember, our device is enumerated as composite HID proprietary / HID standard keyboard. This makes it completely driverless for all operating systems and enables standalone operation as the Mooltipass can type logins and passwords selected through its user interface. Management communications are therefore done through the Mooltipass HID proprietary interface, which Chrome 38 now natively supports through its chrome.hid API. The simpler our installation process is, the more likely the final users will appreciate the fruit of our hard labor.

As our last post mentioned there’s still plenty of space for future contributors to implement new functionalities. Our future crowdfunding campaign will allow us to find javascript developers for the remaining app & extensions tasks and also implement other browsers support. Want to stay tuned of the Mooltipass launch date? Subscribe to our official Google Group!

 

Using A Standard Coil For NFC Tag Implant Reading

October 8, 2014 by 18 Comments

A few months ago Hackaday covered the xNT crowdfunding campaign which aimed at making an NTAG216 based NFC implant for different purposes. I actually backed it, found that standard NFC readers don’t perform well and therefore decided to try using a standard coil as an antenna for better reading performances.

Most NFC readers typically only have a small sweet spot where implant reading is possible. This is due to what we call coupling factor which depends on the reading distance and reader & NFC tag antenna geometries. Having a smaller antenna diameter increases the coupling factor and makes implant positioning easier.

In my detailed write-up you’ll find a good introduction to impedance matching, a process where a few passive components are added in series/parallel with an antenna to bring its complex impedance close to a RF signal transmitter’s. This usually requires expensive tools but allows optimal power transmission at a given frequency.

You may find our xNT coverage here.

Developed On Hackaday: Sometimes, All You Need Is A Few Flags

October 1, 2014 by 26 Comments

The development of the Hackaday community offline password keeper has been going on for a little less than a year now. Since July our beta testers have been hard at work giving us constant suggestions about features they’d like to see implemented and improvements the development team could make. This led up to more than 1100 GitHub commits and ten thousand lines of code. As you can guess, our little 8bit microcontroller’s flash memory was starting to get filled pretty quickly.

One of our contributors, [Miguel], recently discovered one compilation and one linker flags that made us save around 3KB of Flash storage on our 26KB firmware with little added processing overhead. Hold on to your hats, this write-up is going to get technical…

Many coders from all around the globe work at the same time on the Mooltipass firmware. Depending on the functionality they want to implement, a dedicated folder is assigned for them to work in. Logically, the code they produce is split into many C functions depending on the required task. This adds up to many function calls that the GCC compiler usually makes using the CALL assembler instruction.

This particular 8-bit instruction uses a 22-bit long value containing the absolute address of the function to call. Hence, a total of 4 flash bytes are used per function call (without argument passing). However, the AVR instruction set also contains another way to call functions by using relative addressing. This instruction is RCALL and uses an 11-bit long value containing the offset between the current program counter and the function to call. This reduces a function call to 2 bytes and takes one less clock cycle. The -mrelax flag therefore made us save 1KB by having the linker switch CALL with RCALL instructions whenever possible.

Finally, the -mcall-prologues compiler flag freed 2KB of Flash storage. It creates master prologue/epilogue routines that are called at the start and end of program routines. To put things simply, it prepares the AVR stack and registers in a same manner before any function is executed. This will therefore waste a little execution time while saving a lot of code space.

More space saving techniques can be found by clicking this link. Want to stay tuned of the Mooltipass launch date? Subscribe to our official Google Group!

Making An Inductor Saturation Current Tester

September 23, 2014 by 9 Comments

[Kalle] tipped us about a quick project he made over a couple of evenings: an inductor saturation current tester. All the components used for it were salvaged from a beefy telecom power supply, which allows the tester to run currents up to 100A during 30us in the inductors to be characterized.

Knowing the limits of an inductor is very convenient when designing Switch Mode Power Supplies (SMPS) as an inadequate choice may result in very poor performances under high loads. [Kalle]’s tester simply consists in a N-Mosfet switching power through a load while a shunt allows current measurements. The saturation point is then found when the current going through the inductor suddenly peaks. As you can see from the picture above, 16 4700uF electrolytic caps are used to compensate for the sudden voltage drop when the Mosfet is activated. A video of the system in action is embedded after the break.

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Using A Theremin For Medical Applications

September 17, 2014 by 30 Comments

[Eswar] is not an ordinary 16 years old boy. He figured out a noninvasive way to measure breathing in hospitals for less than $50. He is using a theremin to measure the rise and fall of a patient’s chest. For our curious readers, this touch-less instrument was invented back in 1929 by the Russian inventor [Leon Theremin]. It uses the heterodyne principle and two oscillators to generate an audio signal. One electronic oscillator creates an inaudible high pitch tone while another variable oscillator is changed by adding capacitance to an antenna.

As you can guess the space between the patient’s chest and the antennas placed around the bed forms a tiny capacitor which varies when exhaling. With three simple TTL chips and a little guessing [Eswar] had a working prototype ready to be implemented in the real world. If you’re interested in theremin, we invite you to see one of our previous articles on how to make one in a few minutes with a soda can.