[Daniel] found himself with a need to connect a single USB device to two Linux servers. After searching around, he managed to find an inexpensive USB switch designed to do just that. He noticed that the product description mentioned nothing about Linux support, but he figured it couldn’t be that hard to make it work.
[Daniel] started by plugging the device into a Windows PC for testing. Windows detected the device and installed an HID driver automatically. The next step was to install the control software on the Windows system. This provided [Daniel] with a tray icon and a “switch” function. Clicking this button disconnected the HID device from the Windows PC and connected the actual USB device on the other side of the USB switch. The second computer would now have access to the HID device instead.
[Daniel] fired up a program called SnoopyPro. This software is used to inspect USB traffic. [Daniel] noticed that a single message repeated itself until he pressed the “switch” button. At that time, a final message was sent and the HID device disconnected.
Now it was time to get cracking on Linux. [Daniel] hooked up the switch to a Linux system and configured a udev rule to ensure that it always showed up as /dev/usbswitch. He then wrote a python script to write the captured data to the usbswitch device. It was that simple. The device switched over as expected. So much for having no Linux support!
Researchers at Ruhr University of Bochum in Germany have been busy working with RFID and related devices for quite some time now. They call the fruit of their labors Chameleon, a versatile Contactless Smart Card Emulator. Contactless Smart Cards are RFID style devices that also contain a smart card style memory. These cards are often used for payment, replacing mag strip style credit cards. Philips MIFARE Classic cards are a common example of contactless smart cards. The Chameleon is set up to emulate any number of cards using the common 13.56MHz frequency band. Adding a new card is as simple as loading up a new CODEC and application to the firmware. Currently Chameleon can emulate MIFARE cards using the ISO14443A.
The Chameleon is completely open source, and can be built for around $25 USD. The heart of the system is an Atmel ATxmega192A3 microcontroller. The 192 is a great microcontroller for this task because it contains hardware accelerators for both DES and AES-128. An FTDI USB interface chip is used to provide an optional communication link between a host computer and the ATxmega. The link can be used for debugging, as well as manipulating data in real-time. A host PC is not necessary for use though – the Chameleon will operate just fine as a stand alone unit. We definitely like this project – though we’re going to be doubling down on the shielding in our RF blocking wallets.
[Raffael] had an old Broken Yamaha natural sound receiver lying around. Rather than throw it out, he built himself a slick web radio. He calls it RadioduinoWRT. [Raffael] started by removing all the internals – though he kept the front panel controls. He then added an Arduino Mega to handle the front panel controls, including a 16×2 character LCD module. The Arduino also takes commands via IR remote. An enc28j60 Ethernet module allows the Arduino to communicate with a the brains of the operation, a TL-WR703N mini router.
A micro USB hub expands the single USB port on the WR703, allowing both a USB sound card and a 4 gig USB stick to be mounted. We’d like to add that the TL-WR703 is a must in this application – the amazon link [Rafael] provides brings up the TL-WR702 as a top link. Only the TL-WR703 has a USB host connection.
The real magic is in [Raffael’s] software setup. The WR703 is running OpenWRT. He added modules for the USB sound card, as well as expanding the file system onto the USB stick. Once that was complete [Raffael] added Music Player Daemon (MPD) and MPC, a console app to drive MPD. Lighttpd, a light web server provides an interface for the Arduino as well as a web front end to the entire radio.All this allows [Raffael] to control his radio in several ways. He can log in via any web browser on his network. He can use the front panel controls. He can use an IR remote. Since he is running MPD, any client (there are literally hundreds out there) will also drive the radio.
While a low-end USB sound card in a home stereo application does make our inner audiophile cringe a bit, the quality does seem to be pretty good. [Rafael’s] design would make it simple to swap out a higher quality USB sound card if the need arises.
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