Department of Electrical and Computer Engineering Team BeepachU November 26, 2013 Midway Design Review

Department of Electrical and Computer Engineering Team 7 Members Eric Wagner EE David Zeifman CSE Mark Wagner EE Quanquan Han EE

3 Department of Electrical and Computer Engineering This Presentation: Overview  Review: What is BeepachU?  Block Diagram: Old and New  Demos: TX/RX and working Audio  CDR deliverables, Team Responsibilites, and Schedule

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5 Department of Electrical and Computer Engineering Review: What is BeepachU?  Problem: Lost items  Solution: Cheap tracking tag that makes sounds to lead you to your item  Key Fob transmits to tag  tag makes sound for user Where’s my Wallet?

6 Department of Electrical and Computer Engineering Review: BeepachU Specifications  Range: 100m (outdoor line of sight)  Battery life: 6 months for both Keyfob and Tag  Weight: Keyfob <.5 lb, Tag <.5 Ib  Response time: under 2 seconds  Size: Keyfob < 4 square inches Tag < 3 square inches  Robust Tag will not be set off by interference signal  Cheap: Each unit < $30 when mass produced

7 Department of Electrical and Computer Engineering Block Diagram

8 Department of Electrical and Computer Engineering Previous Block Diagram

9 Department of Electrical and Computer Engineering Redesigned Block Diagram

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11 Department of Electrical and Computer Engineering Block Diagram: ANT SoC Block  Contains the nRF51422 “ultra low power” ANT SoC  ANT, like bluetooth, is a network protocol  ANT is pre-implemented in software on the chip  Programmed in C

12 Department of Electrical and Computer Engineering Block Diagram: Network Diagram (using ANT protocol)  ANT Protocol uses time-division multiplexing to separate channels  Master and Slave devices are preset only to connect with eachother

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14 Department of Electrical and Computer Engineering Block Diagram: Speaker System  LM 386 audio amplifier- $0.34  CDM Ohm speaker- $0.79  2.9mm height, 10mm diameter

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16 Department of Electrical and Computer Engineering Block Diagram: User Interface

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18 Department of Electrical and Computer Engineering Block Diagram: Power Supply  3V CR-2032/VP Energizer coin cell battery  225mAh lifespan  0.79” diameter x 0.13” height  $0.40 per battery  One battery per keyfob, two per tag

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20 Department of Electrical and Computer Engineering Block Diagram: Antenna + PCB  Same PCB used for keyfob and tag (reduces cost)  PCB = 1.2 x 1.5 inches  “Inverted F” antenna integrated into PCB Isotropic, often used in cell phones Can be tuned manually by scraping copper off its end

21 Department of Electrical and Computer Engineering Demonstrations

22 Department of Electrical and Computer Engineering Review of Proposed MDR Deliverables  Demonstration of working TX/RX TX and RX recognize each other and work at close distance TX and RX hardware not necessarily contained in small package (may be on a breadboard or Development Kit Module) Not yet battery powered  Working speakers driven by TX/RX hardware Small audio system will be operational Same transceiver SoC that drives TX/RX must be able to drive audio system. Not yet battery Powered

23 Department of Electrical and Computer Engineering Demonstration  Transmit/Receive Demo  Audio Demo  Enjoy

24 Department of Electrical and Computer Engineering CDR Deliverables, Team Responsibilities, and Schedule

25 Department of Electrical and Computer Engineering Proposed CDR Deliverables  Fully functional system Doesn’t necessarily meet specs, but works Powered by battery Implemented on custom PCB not development board Hot cold feature implemented Beep will work and will be audible

26 Department of Electrical and Computer Engineering Individual Responsibilities Dave Zeifman  Produce finalized & power efficient BeepachU TX/RX code Eric Wagner  Order and Test PCB module with integrated Antenna  Tune Antenna for optimal performance Mark Wagner  Produce finalized audio driving code Quanquan Han  Produce packaging + integrate packaging with PCB

27 Department of Electrical and Computer Engineering Schedule

Department of Electrical and Computer Engineering Questions? Thank You

29 Department of Electrical and Computer Engineering Power Specifications (with 3.3V source)  Keyfob (on) Sleep mode = 8.25uW (or 2.5uA) Transmitting as master device = 8.58mW (or 2.6mA) Transmitting + LED on = 16.8mW (or 5.1mA) Battery indication LED = 8.25mW (2.5mA)  RX (always on) RX sleep/search mode (10% duty cycle) = 262.2mW (or 79.5uA) Paired as slave device = 8.58mW (or 2.6mA) Paired as slave + beep and blink= 640.2mW (or 194mA)

30 Department of Electrical and Computer Engineering Power Usage Estimations  Keyfob (TX) is on for about 2 minutes per use Transmitting + LED on (for Hot/cold): 120s Battery indication LED: 120s Total = 912 mAs = mAh (888 uses)  Tag (RX) is used for 2 minutes per use Hot/Cold active (connected) : 115s Beep & LEDs active: 5s Total = 1269mAs = mAh (297 uses)  Tag (RX) is on sleep/search mode for the rest of the time

31 Department of Electrical and Computer Engineering Preliminary Cost Analysis  “Each unit < $30 when mass produced” Part (quantity)Quantity (keyfob) Quantity (Tag) Cost Chip Cap/Ind/Resistors17 $0.01 x 17 = $0.17 nRF51422 (ANT SoC)11$3.13 NX2520SA 16 MHz crystal11$0.51 LM386 Audio Amp11$0.34 LED22$0.50 x 2 = $1.00 Speaker01$0.79 Battery12$0.40 x 2 = $0.80 PCB11$5.00 Total:$10.95$11.74$22.69

32 Department of Electrical and Computer Engineering Multiple Tags for a Single Keyfob?  ANT allows for “star networks” with one master (keyfob) and multiple slaves (tags)  Tags must be paired with masters during initial programming  multiple tags will have to be bought alongside the keyfob

33 Department of Electrical and Computer Engineering ANT Network Security  Can use Single Channel Encryption 128-bit AES-CTR (symmetric algorithm – single shared key) Supports multiple slaves per master on single channel, but only one channel per master

34 Department of Electrical and Computer Engineering Responsibilities : Dave Zeifman  Keyfob Programming Keyfob must initiate connection with tag when hot/cold is active Must display RSSI in accurate manner using LED Must be power efficient  Tag Programming Tag must constantly search for Keyfob Tag must know when to connect and when to beep Must be power efficient

35 Department of Electrical and Computer Engineering Responsibilities : Mark Wagner Sound Driver Store “Beep” sound bite in chip Write audio driving code for receiver Generate pleasant and audible beeping sound Acceptable power consumption

36 Department of Electrical and Computer Engineering Responsibilities : Eric Wagner  PCB Must be able to support all buttons/LEDs/speakers on UI Must fit size specifications Must be cheap enough to produce on BeepachU budget  Antenna Must be nearly isotropic in tag, can be directional in keyfob Must have high enough efficiency to meet range requirements Must be tunable

37 Department of Electrical and Computer Engineering Responsibilities: Quanquan Han  UI/Packaging Must fabricate packaging Fabrication should be within BeepachU budget Buttons, LEDs and Speakers must be integrated into package Package must not muffle tag beeps Package must not interfere with antenna