TuxPhone Deva Seetharam France Telecom Research Surj Patel

Tux-Phone Deva Seetharam, France Telecom Research Surj Patel

BACKGROUND

Motivation Cyber Shepherd Of course, Paris Hilton Grameen Phone n Many people think cell phone is the best thing since the sliced bread. Right? n It is an excellent hacking and application platform. However, we are not able to exploit its full potential because…. .

Motivation (continued) Cell Phone Vendors

Motivation (continued) n Adding new hardware/software features to commercial cell phones is expensive: $10, 000 licensing fee + royalty fee for every RFID reader added to cell phones.

Motivation (continued) n The APIs and architecture are closed. It is difficult to add any new features. For instance, one cell phone vendor requires the following components just to read a NFC tag: Solaris 9, Oracle 9 i Enterprise Edition, Bea Web. Logic Server 8. 1 SP 2 Enterprise Edition, Java 2 SDK Standard Edition version 1. 4. 2 and support for SSH.

PROPOSED SOLUTION

Tux-Phone n An open cell phone platform named tux- phone. n Three important disclaimers: It is not a novel idea. People have thought and written about similar equipment. n We just started building it. n The engineering process is fairly straightforward except for finding the right parts and putting them together while keeping it small. n

System Architecture LCD Ringer Computing Engine RF Module Speaker Battery Keypad Mic

Computing Engine n Options n A custom microcontroller board with custom firmware n A custom microcontroller board with a small OS like Ethernut n An Off-The-Shelf (OTS) board with a custom OS n An OTS with Linux

Computing Engine (continued) We decided to use an OTS board with Linux. n Advantages n n n Open source Free Excellent support for different protocol stacks Active development community Extensive support for application development Disadvantages n n n Not power-efficient Not a real-time operating system Requires plenty of resources

Computing Engine (continued) n We chose Gumstix, a tiny Intel XScale based Linux SBC. • Intel XScale® PXA 255 400 MHz • Full Linux • Small - 80 mm x 20 mm x 6. 3 mm • Wide operating voltage - 3. 4 - 5. 2 V • Two headers for expansion boards • Excellent software support: Busybox, Boa, uclibc, ssh, Berkeleydb, Bluez etc.

RF Module + Antenna n Requirement: A module that can handle all RF communication and provide AT command interface. n Not too many vendors. A few prominent ones are Siemens, Nokia, Falcom and Telit. n These modules were primarily designed for machineto-machine (M 2 M) communications. Embedded Network Enterprise Network Node 1 DB Node 2 Remote Application GSM Module Gateway / Reader Node n

RF Module + Antenna (continued) n We chose GM 862 module from Telit. • Supports 900 MHz, 1800 MHz and 1900 MHz frequencies • Works with all SIM card providers currently - AT&T, T-Mobile, and Cingular. • 17 m. A average stand-by, 3. 5 m. A in low-power mode, 250 m. A ave. operating current • Support for GPRS, Voice, SMS, Fax and Camera • Data rate up to 57. 6 kbps

Display n Gumstix CPU (PXA 255) has a built-in LCD controller that can be used to drive LCD modules using the Linux PXAFB driver. n We are using SEIKO Color STN 1. 5” (RNH 942209 R 1 A) Cell Phone Display.

Display (Continued) n Adding LCD support in PXA Linux kernel is fairly straightforward (and well-documented). However, hardware interfacing is tedious due to lack of a proper breakout board. Two options: Use an adapter board n Create an appropriate breakout board. n Gumstix Breakout-gs Adapter LCD

Audio n A cell phone requires three audio components: n Speaker n Microphone n Ringer n GM-862 supports both hands-free and handset mode. n We have tried only the handset mode.

Speaker n GM-862 requires a speaker with the following characteristics: 16 ohm impedance, signal bandwidth of 150 – 8000 Hz at -3 db and maximum power output of 30 mw.

Speaker (continued) n We are using Panasonic EAS-4 D 02 C 0 speaker. This speaker is relatively large (4 cm long) and we are looking for smaller alternatives. n In particular, we are considering Regal Micro speakers.

Speaker (continued) n We are also considering fascinating speaker products from Nxt. Sound, UK. Distributed Mode Behavior Distributed Mode Actuator n Sound waves are generated by initiating and exploiting multiple, organized bending resonances in the panel. Using this technology, LCD protective cover or the keypad can be converted into a speaker.

Microphone n GM-862 manufacturer recommends balanced and buffered microphone. n Biasing circuitry is also necessary to eliminate noise. n We are thinking of using Star Micronics MAA-04 B-SA 2 Series. n This microphone is attractive because it is small (5. 6 x 3 mm), wide operating voltage (1 – 10 v) and -45 db sensitivity.

Microphone (continued) n Another interesting microphone from Star Micronics: 3 mm diameter MAA-03 A-L.

Ringer n We are just using a piezo audio indicator (CEP- 2242) as a ringer for simplicity reasons. n However, a sophisticated ringer can be built using the following design: Audio Codec (UCB 1400) Low Distortion Audio power amplifier (SSM 2211) Gumstix Speaker GM-862

Keypad n We are using a Gray Hill 3 x 4 keypad. n The keypad is connected to Gumstix using the following configuration. 3 x 4 KEYPAD R 1 R 2 R 3 R 4 KEY ENCODER R 1 R 2 R 3 R 4 D 0 – D 3 MM 74 C 922 C 1 C 2 C 3 Gumstix DA C 1 C 2 C 3 C 4 n This Keypad is large. It needs to be replaced with a small custom keypad.

Battery n Gumstix takes 3. 4 – 5. 2 V supply and draws maximum 250 m. A current (no bluetooth). n GM-862 module requires 3. 4 – 4. 2 V and draws a maximum of 1. 9 A current. n Other considerations - , battery must be light, safe, rechargeable (several hundred times), easily available and must have a good shelf life. n Considered Ni. Cd, Ni. MH and Lithium batteries.

Battery (continued) n Nickel Cadmium n Available only in cylindrical shapes. n 3 -4 cell pack would be required since a cell supplies only 1. 2 v. n Cadmium is a toxic metal and requires special disposal. n Suffers from fast self-discharge. n Nickel Metal Hydride n Available in cylindrical and coin cell form factors. n High current capacity. n 3 -4 cell pack would be required since a cell supplies only 1. 2 v. n Suffers from fast self-discharge.

Battery (continued) n Lithium Polymer Batteries n Available in 3. 7 V. n Current capacity – 2000 m. Ah n Can support continuous discharge at 2 C n No special disposal requirements n Rechargeable for several hundred times (not as good as Ni. MH) n Fast recharge n Slow self discharge n Cool batteries – they were used to power i. Pods.

Packaging (Back) Battery GM-862 85 Gumstix 55

Packaging (Front) LCD Speaker Buzzer 125 Keypad 69 52 Microphone

Software Tux Application PXAFB Tux Driver RI LCD Keypad GM-862

Software (continued) n Kernel space code is kept minimal due to the following (obvious) reasons: n Any misbehaving driver can impact the whole system n Kernel API changes much more frequently than the user space API n User space libraries have more features and functionality than kernel space libraries.

Closing Comments

Discussions n Why are you doing this? n To create an open hacking and research platform for us and for everyone. n What is the big deal? n Nothing. As it was described, building a cellphone is simple, but not necessarily easy. n What is the main challenge? n Stitching together multiple components while keeping the size down is the main challenge.

Discussions (continued) n How much would it cost? Approximately, $400. Gumstix Connex 200 114. 00 GM-862 109. 95 Antenna 12. 95 LCD 17. 00 Keypad 25. 00 Keypad Encoder 7. 44 Buzzer 2. 64 Microphone 3. 00 Speaker 8. 00 Battery 12. 95 Passive components 20. 00 Breakout Board 50. 00 Enclosure 10. 00

Discussions (continued) n Does it make sense? n Hope so. We have met several researchers/hackers/small businesses that could use an open cell phone platform like this one. n Why not use a Linux PDA? n Hardware schematics are usually not available. Modifying those PDA-based cell phones can be difficult. n What next? n n n Create a cell phone breakout board Find a small antenna Find a small keypad Complete drivers Complete applications

Discussions (continued) n Is the project sustainable? n Not sure. Unlike software open source projects, as you can imagine, hardware projects are expensive. Unlike there is funding, it may not be possible to continue the project.

Thank You! Gracias! Merci!

Acknowledgements n Colin Cross – a master hacker and a friend n Gumstix community n GM-862 community

Resources n Round Solutions – http: //www. roundsolutions. com n Gumstix – http: //www. gumstix. com n Spark. Fun – http: //www. sparkfun. com n Digi. Key – http: //www. digikey. com n Mouser – http: //www. mouser. com n Linux HOWTO – http: //www. tldp. org n Linux Device Drivers - http: //lwn. net/Kernel/LDD 3/ n Linux Kernel – http: //www. kernel. org n Blog – http: //www. surjpatel. com