Presentation given to the Stockholm Internet of Things meetup about my smartwatch hobby project.

1. Yet Another Smartwatch
My latest hobby project
Erland Lewin

2. Erland Lewin
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Computer Science KTH
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VC-backed startup Voxi doing Speech Recognition & Language
Understanding
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Licentiate degree in Biological Physics
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Currently at Avalon Innovation, Consultant, System Designer
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Hobby electronics since a couple of years
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Family, two kids

3. Wristwatch
project
Watches are cool
Low Power
Small size
Engineering challenge

5. Sharp Memory LCD

6. Components

7. Components (23 tabs)

8. BOM cost @ 100 = 270 SEK,
@1=344

9. Schematic

10. Processor
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PIC XLP
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Energy Micro
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Nordic Semiconductor

11. PCB Layout

12. Nordic Semi nRF51822
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ARM Cortex M0 core
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Low power (2 µA sleep)
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30 SEK @ 1, 20 SEK @ 100
(10 SEK more than ATMega)
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●
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Reasonable Dev kit (700 SEK)
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Pin mapping
Great support
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Norwegian !?
Bluetooth Low Energy
Realtime Counter
256 kB Flash, 16 kB RAM

13. BLE / iOS
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Low power
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No Special License
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Apple Notification Center Service (ANCS) built in
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iPhone 4S and later

14. Low Power Design
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Low voltage!
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Frequency not so important
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Think Power, not Current
Leakage
Battery self discharge, max
current
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Theory and practice
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Design shunt resistors
Sleep woken by interrupts

15. Radio
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Antenna affected by everything
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Certification
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Network Analyzer (100 kSEK?)

16. The Road Ahead
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Review Schematic, Layout
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Order boards, Parts
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Learn BLE, program software
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Solder boards
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Design case, 3D print
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...
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Profit! ;-)