Prior to iOSDevCamp, I had been looking into Hector Martin’s usbmux implementation for linux. The main goal of his project was to provide usb syncing for iOS devices on linux machines. Upon further investigation, I found usbmux sets up a local socket that relays information to an Apple daemon running on the iOS device. This daemon then relays the information via tcp to other daemons on the device. In short, usbmux allows applications on the desktop to talk to tcp-based servers running on the device without using private APIs or modifications to the OS, all over usb.

My hackathon demo was fairly straight-forward.
1. Make an iPhone app that listens on a predetermined tcp port.
2. Make a Mac app that uses usbmux to talk to the iPhone app tcp server.

Side Note: The mac app can also choose to talk to the iPhone app via wifi without any modification to the iPhone app. Which is beautiful. If Apple comes along and breaks usbmux or adds in protections for app store apps, the mac app can fallback to talking to the device over wifi with no modification to the iPhone app.

Ideally, the mac application would talk directly to the unix domain socket /var/run/usbmuxd. However, due to lack of time from working on other hackathon projects, I took a shortcut. Hector Martin’s usbmuxd source code repo contains a wonderful python utility called tcprelay. Tcprelay forwards any port on the local machine to any port on an iOS device using usbmux. For the demo, I’ve set this up to relay port 20000 on my local machine to my iOS device where my iPhone app is listening.

My client/server setup is using serialized plists to transfer information. The first 32 bits are the size of the data to be received.

To get the demo up and running:
1. Compile Server/Server2 and place it on your iOS device.
2. run “$ ./tcprelay -t 20000:20000″ to relay local port 20000 to remote port 20000 via usbmux.
3. Start up Server/Server2
4. Start the corresponding MacUSBSyncClient. (The server _must_ be running before you start the mac client)

MacUSBSyncClient/Server will send a string and an image for display on the device. Due to my horrible unix socket implementation, the images must be <1mb. MacUSBSyncClient2/Server2 requests the most recent barcode scan from the iPhone. The iPhone server will constantly be checking for bar codes via the camera preview. Upon a successful scan, it saves the barcode image and data. Pressing "Scan" in the client will grab this information from the iPhone and display it on the mac. The product can then be looked up via the "Lookup" button.

I'm working on a much cleaner implementation that I'll be posting asap. It will talk directly to /var/run/usbmuxd instead of requiring tcprelay. However, for those interested, here is the source code I used in the demo at iOSDevCamp2010. Please note it was written in less than a day and is _extremely_ ugly.

iOS USB Sync Demo

For those interested in integrating this into their application. Shoot me an email Max@MaxWeisel.com, I’d love to help!

Max

UPDATE: MiTube is officially down. Top 7 in less than 24 hours!

Max

The incredible volume and clarity was achieved using a simple, yet efficient design concept. A vibration-free, pressurized aircraft grade aluminum enclosure. The sealed designed offers the low friction features of an enclosure-less design, yet with the lower mechanical loss of an enclosure based design. Thus producing a full sound with little to no interference from enclosure vibration.

YG Acoustics:

“Carmel utilizes Scan-Speak drivers, modified to YG Acoustics specifications. The tweeter, which is assembled in house, is a highly modified ring-radiator type. It offers greatly extended frequency response, linearity, and power handling. The 7” woofer in the Carmel is a modified Scan-Speak Revelator and provides excellent clarity and bass extension in a compact enclosure.”

Don’t let their appearance fool you, these speakers easily compete with the sound of their larger counterparts while remaining a reasonable size for anyone. I’ve included a picture and specifications of the speakers demonstrated at the conference.

Technical Specifications

Deviation: Less than +/- 2 db in the audible band. Useable output from below 35 Hz to above 40 kHz
Filters: Proprietary DualCoherent™ crossover. Provides ultra-flat frequency response with less than 10° relative phase.
Sensitivity: 87 dB.
Impedance: 8 ohms nominal. Minimum below 4 Ohms at 4 kHz.
Dimensions: 102 cm x 28 cm x 36 cm (40.25” x 11” x 14.25”) H x W x D.
Weight: 30 kg (66 lbs) net weight per channel, 80 kg (177 lbs) shipping weight per pair.

(YG Acoustics constantly strives to update and improve existing products as well as create new products and technologies. Therefore, the specifications and construction details are subject to change without notice.)

If you’re interested in playing this style of music, I suggest you check out Michael Hedges. One of Mckee’s primary influences, Hedges songs include unique tunings and innovative playing styles I’ve come to enjoy.

Materials:
1 x Jansport backpack
2 x 91.2W Peltier Units – ( 12v * 7.6a = 91.2W )
2 x Processor Heat Sinks w/ Fan
1 x Tube of Thermal Gel
1-2 x 12V 5lbs Motorcycle battery
2 x Different Size Tupperware Containers
1 x 8.5×11 Piece of Sheet Metal
1 x Switch
Some Spare Wire

Procedure:
Step 1: Cut the piece of sheet metal to the preferred size. Make sure it fits on the back of the backpack!

Step 2: Make some holes around the perimeter of the piece of sheet metal. These will be used later to attach the metal to the backpack.

Step 3: Measure where the peltier units will be placed. Make sure when the heat sinks are spaced apart so the heat sinks will fit! Then drill the holes required to attach your heat sink above the peltier units.

Step 4: Apply some thermal gel to each heat sink. Add a peltier unit to each heat sink and put thermal gel on top of each peltier unit. Then apply thermal gel to the spaces on the sheet metal where each peltier, heat sink pair will be placed.

Step 5: Using the screws included with each heat sink, attach them to the sheet metal through the holes drilled earlier.

Step 6: Now that the cooling unit has been made, an air venting system needs to be made. To do this, get a tupperware that seals everything between the fan and the sheet metal and cut a hole in the bottom that matches the fans. Then get another tupperware on top that will act to cover the fans from the back of the backpack and guide in air from the sides. The fans will be blowing air onto the heat sinks, so air will come in the sides of the top tupperware and get blown on the heat sinks and then released out into the open.

Step 7: Try connecting the fan wires in different combinations until the positive and negative leads are found. Make sure when connected the fans blow air on the heat sinks. Then solder the wires of each fan to those of the peltier units in parallel. Now connect each peltier, heat sink pair together in series.

Step 8: Cut a hole in the backpack that’s just a little smaller than the piece of sheet metal. Cover the seams with duct tape so they don’t fray. Now use some thick thread or thin wire to sew the sheet metal to the back of the backpack.

Step 9: Now use some thick thread or thin wire to sew the sheet metal to the back of the backpack

Step 10: Now cut a hole on each side of the backpack for air intake. Then cut one more at the top to let the warmer air out. I cut mine around the neck because by the time it reaches the top of my backpack it was slightly cool.

Step 11: Solder one lead of some wire to a wire going to the cooling unit. The two leads left will connected to the battery while the two leads on the other end of the wire will be for the switch.

Step 12: Zip up the backpack and turn it on!

Modifications:
I recommend putting a mesh screen over the vents to keep big particles out of the fans. If you want to make this into a heating backpack reverse the leads on the peltier units so the hot side is on the sheet metal and the cool side is on the heat sinks.

I hope you all enjoy it :)

Max

Max