A Shareable Wireless Biometric Flash Drive

Wireless storage and biometric authentication are both solved problems. But as [Nathan] and [Zhi] have noticed, there is no single storage solution that incorporates both. For their final project in [Bruce Land]’s ECE 4760, they sought to combine the two ideas under a tight budget while adding as many extras as they could afford, like an OLED and induction coil charging.

final_product_600Their solution can be used by up to 20 different people who each get a slice of an SD card in the storage unit There are two physical pieces, a base station and the wireless storage unit itself. The base station connects to the host PC over USB and contains an Arduino for serial pass-through and an nRF24L01+ module for communicating with the storage side. The storage drive’s components are crammed inside a clear plastic box. This not only looks cool, it negates the need for cutting out ports to mount the fingerprint sensor and the OLED. The sensor reads the user’s credentials through the box, and the authentication status is displayed on an OLED. Files are transferred to and from the SD card over a second nRF24L01+ through the requisite PIC32.

Fingerprint authorization gives the unit some physical security, but [Nathan] and [Zhi] would like to add an encryption scheme. Due to budget limitations and time constraints, the data transfer isn’t very fast (840 bytes/sec), but this isn’t really the nRF modules’ fault—most of the transmission protocol was implemented in software and they simply ran out of debugging time. There is also no filesystem architecture. In spite of these drawbacks, [Nathan] and [Zhi] created a working proof of concept for wireless biometric storage that they are happy with. Take a tour after the break.
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Hacking a NRF24L01 Radio for Longer Range

[RonM9] wasn’t happy with his 50 foot range on his NRF24L01 project. The RF had to cut through four walls, but with the stock modules, the signal was petering out after two or three walls.  A reasonably simple external dipole antenna managed to increase the range enough to do the job.

[RonM9’s] instructions show where to cut away the existing PCB antenna and empirically tune the 24 gauge wire for best performance. He even includes an Arduino-based test rig so you can perform your own testing if you want.

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Controlling Quadcopters With Wireless Mouse Dongles

Last week we gave away a few Crazyflie 2.0 quadcopters to some cool Hackaday Prize entries. This quadcopter ships with the intention of being controlled by your smartphone. But it can also be controlled by a PC with USB dongle and an nRF24LU1+ SOC. [ajlitt] didn’t figure out he wanted the USB dongle (the Crazyradio) that can control this quad until after he used his gift code to claim his Crazyflie quad. No matter; the dongles for Logitech wireless keyboards and mice use the same radio as the Crazyflie and can be modded to make this quad fly.

The board inside the Logitech unifying receiver is a simple affair, with some pads for the USB connector, a crystal, the nRF24LU1+ radio module, and a few passives. To get this radio chip working with his computer, [ajlitt] simply needed to break out the SPI pins and wire everything to a Bus Pirate.

Getting the Crazyradio firmware onto this proved to be a little harder than soldering some magnet wire onto a few pins. The chip was first flashed without a bootloader, a full image with the bootloader was found, after wrangling a single byte into place, [ajlitt] had a working Crazyflie radio made from a wireless mouse dongle. The range isn’t great  – only 30 feet or so, or about as far as you would expect a wireless mouse to work. Excellent work, even if [ajlitt] is temporarily without a mouse.

The Crazyflie 2.0 is available from the Hackaday Store, along with the add-ons if you don’t want to hack your own.

Embed with Elliot: Multiplexing SPI Uses Few Pins

[Ralph Doncaster], aka Nerdralph, seems to be absolutely driven to see how few resources he can use on a microcontroller to get the job done. In this post on his blog, [Ralph] writes some custom bit-banged SPI code to cut the number of SPI lines necessary to drive an nRF24L01+ radio module from four down to two. That really helps if you’re using a micro with only six free pins, like an ATtiny85.

If you’re going to say, “why don’t you just buy a bigger microcontroller?”, you’re missing the point. This exercise strikes us as optimization for optimization’s sake and a dirty hack, both of which are points in its favor.  There are also a couple of techniques here for your mental toolbox. We thought it was interesting enough to look at in depth.

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ShakeIt – an interactive light game

Learning becomes interesting when you make it fun, interactive and entertaining. [Arkadi] built ShakeIt – an interactive game for the Mini MakerFaire in Jerusalem to demonstrate to kids and grownups how light colors are mixed. It is a follow up to his earlier project – Smart juggling balls which we featured earlier.

The juggling balls consist of a 6 dof sensor (MPU 6050), a micro controller, transmitter (NRF24L01+), some addressable RGB LED’s and a LiPo battery. An external magnet activates a reed switch inside the balls and triggers them in to action. The ShakeIt light fixture consists of an Arduino Nano clone, NRF24L01+ with SMA Antenna, buck converter, 74 addressable RGB LED’s, and a bluetooth module. The bluetooth module connects to a smartphone app.

[Arkadi] starts out by handing three juggling balls, each with a predefined color (Red, Green, Blue). When the ball is shaken, the light inside the ball becomes stronger. The ShakeIt light fixture is used as a mixer. It communicates with the balls and receives the value of how strong the light inside each of the smart balls is, mixing them up, and generating the mixed color.

The fun starts when the interactive game mode is enabled. Instead of just mixing the light, the Light fixture generates patterns based on how strong the balls are shaken. At first the light fixture shows all three colors filling up the central ball. The three contenders then fight out to get their color to fill up the sphere completely until only one color remains and the winner is declared.

The kids might be learning some color theory here, but it seems the adults are having a “ball” playing the crazy game. If you’d like to build your own shoulder dislocating ShakeIt game, head over to [Arkadi]’s github repository for the ShakeIt and the Juggling Balls. Check the video below to see the adults having fun.

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How Cheap Is Cheap?

The Nordic Semiconductor nRF24L01 is the older sibling of the nRF24L01+ and is not recommended for new designs anymore. Sometimes, if you’re looking for a cheaper bargain, the older chip may the way to go. [necromant] recently got hold of a bunch of cheap nrf24l01 modules. How cheap ? Does $0.55 sound cheap enough?

Someone back east worked out how to cost-optimize cheap modules and make them even cheaper. At that price, the modules would have severe performance limitations, if they worked at all. [necromant] decided to take a look under the hood. First off, there’s no QFN package on the modules. Instead they contain a COB (chip on board) embedded in black epoxy. [necromant] guesses it’s most likely one of those fake ASICs under the epoxy with more power consumption and less sensitivity. But there’s a step further you can go in making it cheaper. He compared the modules to the reference schematics, and found several key components missing. A critical current set resistor is missing (unless it’s hiding under the epoxy). And many of the components on the transmit side are missing – which means signal power would be nowhere near close to the original modules.

The big question is if they work or not ? In one test, the radio did not work at all. In a different setup, it worked, albeit with very low signal quality. If you are in Moscow, and have access to 2.4Ghz RF analysis tools, [necromant] would like to hear from you, so he can look at the guts of these modules.

Thanks to [Andrew] for sending in this tip.

Nordic NRF24L01+ – Real vs Fake

[zeptobars], the folks behind all the decapping hard work and amazing die shots are at it again. This time they decided to look under the hood of two identical looking Nordic nRF24L01+ chips.

The nRF24L01+ is a highly integrated, ultra low power (ULP) 2Mbps RF transceiver IC for the 2.4GHz ISM (Industrial, Scientific and Medical) band. Popular, widely used and inexpensive – and the counterfeit foundries are drawn to it like honey bees to nectar. But to replicate and make it cheaper than the original, one needs to cut several corners. In this case, the fakes use 350nm technology, compared to 250nm in the original and have a larger die size too.

These differences mean the fakes likely have higher power usage and lower sensitivities, even though they are functionally identical. The foundry could have marked these devices as Si24R1, which is compatible with the nRF24L01 and no one would have been wiser. But the lure of higher profits was obviously too tempting. A look through Hackaday archives will dig up several posts about the work done by [zeptobars] in identifying fake semiconductors.