Midway Design Review
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Transcript of Midway Design Review
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Department of Electrical and Computer Engineering
Team BeepachUNovember 26, 2013
Midway Design Review
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Department of Electrical and Computer Engineering
Team 7 Members
Eric WagnerEE
David ZeifmanCSE
Mark WagnerEE
Quanquan HanEE
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3Department 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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4Department of Electrical and Computer Engineering
Review
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5Department 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?
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6Department 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
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7Department of Electrical and Computer Engineering
Block Diagram
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8Department of Electrical and Computer Engineering
Previous Block Diagram
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9Department of Electrical and Computer Engineering
Redesigned Block Diagram
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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
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12Department 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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13Department of Electrical and Computer Engineering
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14Department of Electrical and Computer Engineering
Block Diagram: Speaker System
LM 386 audio amplifier- $0.34 CDM-10008 8 Ohm speaker- $0.79 2.9mm height, 10mm diameter
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16Department of Electrical and Computer Engineering
Block Diagram: User Interface
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18Department 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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19Department of Electrical and Computer Engineering
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20Department 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
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Demonstrations
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22Department 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
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Demonstration
Transmit/Receive Demo Audio Demo
Enjoy
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24Department of Electrical and Computer Engineering
CDR Deliverables, Team
Responsibilities, and Schedule
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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
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Individual Responsibilities
Dave ZeifmanProduce finalized & power efficient BeepachU TX/RX code
Eric WagnerOrder and Test PCB module with integrated AntennaTune Antenna for optimal performance
Mark WagnerProduce finalized audio driving code
Quanquan HanProduce packaging + integrate packaging with PCB
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27Department of Electrical and Computer Engineering
Schedule
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Department of Electrical and Computer Engineering
Questions?
Thank You
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29Department 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)
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30Department 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 = 0.2533 mAh (888 uses) Tag (RX) is used for 2 minutes per use
• Hot/Cold active (connected) : 115s
• Beep & LEDs active: 5s
• Total = 1269mAs = 0.3525mAh (297 uses)
Tag (RX) is on sleep/search mode for the rest of the time
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31Department of Electrical and Computer Engineering
Preliminary Cost Analysis
“Each unit < $30 when mass produced”
Part (quantity) Quantity (keyfob)
Quantity(Tag)
Cost
Chip Cap/Ind/Resistors 17 17 $0.01 x 17 = $0.17
nRF51422 (ANT SoC) 1 1 $3.13
NX2520SA 16 MHz crystal 1 1 $0.51
LM386 Audio Amp 1 1 $0.34
LED 2 2 $0.50 x 2 = $1.00
Speaker 0 1 $0.79
Battery 1 2 $0.40 x 2 = $0.80
PCB 1 1 $5.00
Total: $10.95 $11.74 $22.69
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32Department 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
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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
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34Department 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
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35Department 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
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36Department 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
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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