VoIPing the iPod Touch



It’s a maker’s dream: turn your homebrew ideas into a concrete reality and then ship that product. This dream came true for iPod hackers Dr. Marián Képesi, “Eok,” and Samuel Vinson. They designed, built, and shipped an iPod touch microphone and developed VoIP (voice over internet protocol) software to place phone calls using that mic.

Last November, Képesi was poking around on his iPod Touch. A postdoc at Austria’s Graz University of Technology, he had previously worked with third-generation iPods and was interested in the new Touch line.

During his explorations, he discovered an important fact about the iPod Touch’s bottom connector port: its line-in audio was active. Live pins meant that the iPod Touch could connect to an external audio source. It was compatible with recording or, better yet, with VoIP for talking over the internet. VoIP compatibility was a long-standing goal of the iPhone and iPod Touch hacker community.

Képesi modded an old iPod docking cable, connecting the line-in pins to live audio, and recorded his first sample. The sound level was very low but the signal was live. Although Apple had shipped the iPod Touch as a “play only” device, Képesi had uncovered its ability to record.

He announced his discovery on the iPod Touch fan forums, and set to work adding an amplifier and boosting the audio-in quality. It took some searching but he finally found a small microphone that would fit inside a standard iPod dock connector.

Képesi then put together his parts list and posted the circuit details so anyone could build the open source, dockable microphone. Together, the parts cost less than 20 euros— about 30 bucks.

Many intrepid makers used these instructions to build their own microphones but many didn’t, or more realistically, couldn’t. Between the fine-detail soldering and the extremely tight space considerations for the dock connector, iPod Touch fans begged Képesi for a pre-built] solution. He handcrafted several more microphones for online acquaintances, but the time investment was prohibitive.

“Ridax” (home.swipnet.se/ridax) is a hobbyist in Sweden who frequents the iPodLinux forum. In 2005, Ridax began working with Taiwanese and Chinese sources to buy iPod dock connector supplies in bulk, which is the only way they’re normally available. He resells these in small quantities to hobbyists who want to build their own iPod accessories. Képesi quickly hooked up with Ridax, whose web support pages provided the iPod connector’s pinouts and other important developer information.

Képesi sent over his design and asked if this was something that could be assembled by automation. Ridax looked it over, checked with his Chinese contacts, and said yes. After building a couple of prototypes locally, Ridax worked with the job shop in China to design and then ship the microphone.

The first order was for 1,200 pieces. Képesi and his small team kept 50 on hand and quickly sold the rest through Ridax’s online storefront. The storefront took care of all fulfillment details, including shipping. Within the first few months, they’d sold more than 1,000 microphones for €29 ($46) each. To give some perspective, this price is similar to those for Belkin and MicroMemo microphones in the United States, but in Europe these products sell for about €80. Képesi and his team were selling their microphone for less than half the going rate.

While Képesi worked on the microphone, hackers Eok (in Germany) and Vinson (in France) worked on the iPod’s VoIP software. Vinson was the author of a VoIP system for the Nintendo, based on the Session Initiation Protocol (SIP).

As Vinson didn’t actually own an iPod Touch, he developed the software “blind.” He compiled his versions and sent them over to Eok for testing.

Before long, the team was able to get basic SIP sessions going and Vinson managed to connect the SIP software into the iPod Touch’s low-level audio system. That’s when the microphone and the software came together.

By New Year’s 2008 you could buy a microphone, download the new Siphon software, and make and receive phone calls by setting up an account with Asterisk or with a VoIP provider like FreeCall or SIPphone’s Gizmo5.

In February 2008, the team decided to split. Vinson wanted to focus on the Siphon software, commercializing it with a French VoIP company. Képesi and Eok committed themselves to further developing the TouchMods project (touchmods.net), focusing on open source hardware and software development for the iPod Touch. After this hugely successful collaboration, they agreed it was time to move on to pursue their specific interests.

» For more information: touchmods.org

» TouchMods useful links: touchmods.wordpress.com/useful-links

» Want to buy your microphone without building it from scratch? Visit Ridax at home.swipnet.se/ridax/touchmic.htm. You can also order dock connector supplies if you’re looking to build your own iPod accessories.

» If you read German, there’s a good interview with the development team at Die Welt: makezine.com/go/diewelt

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Erica Sadun

Erica Sadun has written, co-written, and contributed to almost 30 books about technology, particularly in the areas of programming, digital video, and digital photography.

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