To start off, this was my first iOSDevCamp and by far it has proven to be my favorite developer event so far. The rules are simple, your app cannot be in the app store unless it’s open source, and it cannot use private apis or require a jailbroken device.

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

I just received a call from Apple Legal. MiTube will be taken out of the App Store within the hour. It’s currently 33 in top free apps! All in less than 24 hours.

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

The previous posts were created for use with my college applications. I plan to start using this site to post new projects I’m working on as well as any open source projects I’ll be starting.

Max

Over the past few days, I’ve been at CES, the Consumer Electronics Show held in Las Vegas. With some amazing technology coming out this year, from 3D TVs to tablet netbooks, I found myself facing YG Acoustics’ Carmel loudspeakers in a high fidelity audio demonstration. This was by far the most fascinating product I had seen at the conference for a few reasons. First, and most importantly, they were the clearest sounding loudspeakers I had heard in my entire life. Hundreds of HiFi loudspeaker manufacturers were demonstrating their latest and greatest, but the response from these specific speakers was incredible. However, I found the hardware used to produce such a full and rich sound to be the most impressive. Most demonstrations had speakers containing a tweeter, a few mids/woofers and occasionally a sub woofer. The Carmel loudspeakers contained only a single tweeter/woofer pair.

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.)

MxTube started off as an iPhone web app that would give the user greater control over YouTube from their device and computer. YouTube’s primary video format is FLV (Flash Video), as their online video player is flash based. However, the iPhone and iPod Touch do not support flash videos. Therefore, Google (YouTube’s proprietor) came up with the elegant solution of distributing videos to mobile devices through the mp4 format. However, high quality mp4 encoded videos were only available to iDevices via an unpublished xml feed that requires authentication through an undocumented means. Thus, the stock YouTube application was the only method available to access decent quality videos on the iPhone or iPod Touch. However, if the user attempts to view videos via their carrier’s cellphone network, the application would default to unwatchably low quality videos. Even if the user had the option of watching high quality videos via the cell network, the wait times would be ridiculous. Whenever I’d want to show videos to my friends, I’d cope with low quality videos or long wait times, it was unbearable. This is when the idea of MxTube was born. “Save the videos to the device! Eureka! It’s so simple!”, I thought. With no prior knowledge of Objective-C or building applications for iDevices, I set out to educate myself on the subject. At the time, Apple had not yet released any information regarding a developer kit. Any native application development was performed strictly through an unauthorized means. Hackers at the time had successfully gained access to the iPhone’s file system and created documentation based on their findings. These documents along with a modified version of the GNU cross compiler allowed me to compile my apps for the device and pursue MxTube. March 4th, 2008 I finished MxTube and released it onto Installer, the App Store of unrestricted devices at the time. The opening page of the application was a news page I’d use to notify users of updates and bugs that needed fixing, etc. Within the hour of publishing the application, that very news page had crashed my home made web server with the extreme amount of traffic it was driving. Therefore, I bought hosting for that single web page, and appended a small advertisement to pay for the costs. Within the hour I had $50 and was making more money than I knew what to do with. I ported MxTube to firmwares 2.x when the iPhone 3G was released, and then 3.x for the iPhone 3GS. Over seven million downloads later, MxTube is one of the most popular applications for unrestricted devices today.

About 4 weeks ago, I saw this video of Andy Mckee playing his song titled Drifting: http://www.youtube.com/watch?v=Ddn4MGaS3N4. I was blown away by his method of combining percussion, rhythm guitar and melody on a single instrument. The song is played in DADGAD tuning. By bringing the low E string down a step to D, power chords can be played by barring the lowest three strings (DAD) with the left hand. While bringing the high B and high E strings down a step allows them to be played openly with the song. After studying his technique, I noticed the melody of the song is played with the right hand, and the rhythm portion with the left hand. I had only been playing guitar for a month at this point, but knew this was the perfect song to cover. I spent four weeks teaching myself to play the song, and this is the end result:

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.

After seeing an Instructable on Digg for making a USB powered fridge, I decided to incorporate the concept into a backpack. For those who don’t know, the USB fridge uses a Peltier Unit to cool the contents. When power is applied, a Peltier Unit makes one side extremely cool and the other side extremely hot. If the power is reversed, the cool side becomes the hot side and visa versa. The only problem with this is the fact that while cooling the users back, the hot side would be accumulating mass amounts of heat inside of the backpack. My solution to this was to use a processor heat sink along with a fan to push this heat out of the backpack. The cool side of the peltier unit is placed on a piece of sheet metal that will be exposed to the users back for cooling and/or heating. Thanks to my friend Miles for helping with the fabrication process! Go check out his site called Motor Mayhem. Here is how I made the backpack:

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

I removed the old stuff here and put up a nice shiny new blog :)

Max