Ben Valdovinos Senior Design Project 2012

1. BT-BOX
Ben Valdovinos

2. Overview
• The BT-Box is a general purpose Bluetooth based data
acquisition system that connects computers or smart
phone to sensors
• Applications in the medical field
• Fall Detection
• Applications in the environmental field
• Temperature and humidity sensing
• BT-Box’s technology is general purpose and its
applications are very diverse

3. Requirements
• Small size: 3.5” x 2.5” x 0.75”
• Bluetooth communication between BT-Box and
computer/phone
• Data storage on micro SD card
• Accepts different sensors and is reprogrammable
• System runs on re-chargeable battery
• Implement Fall-Detection Algorithm
• Design PCB to place all components in small area
• Optional: Development of smart phone interface

4. BT-Box Small enough to be worn at the
waistline when used for Fall
Detecting
A whole system is being created

5. System Level Block Diagram

6. Existing
• ioBridge
• Internet-enable anything!
• Attach sensors/actuators to a web
gateway or module and control via
cloud services
• 100$
• Life Alert
• Summon help at the push of a button
• Limited to in/around home

7. Microcontroller
Operating Clock Flash IO
Brand RTCC Price
Voltage Speed Memory Pins
Microchip 80
3.3 128 KB Yes 85 5.17
PIC32MX3XX MHz
Flexis Coldfire 66
3.3 128 KB No 134 3.21
MCF21X MHz
Atmel
66
AT32UC3A01 3.3 128 KB Yes 144 4.40
MHz
28
Analog 10
3.3 32 KB No 14 5.15
ADUC7060 MHz

8. Accelerometer
• ADXL345 from “Analog Devices”
• 3mm x 5mm x 1mm
• 23uA in measurement mode and 0.1uA in standby mode
at 2.5 V
• 3-axis measurement with 10-bit resolution
• Up to 16g (1° accuracy)
• Embedded memory with FIFO technology
• Activity/inactivity monitoring
• Single and double-tap detection as well as free-fall
detection

9. Memory Card
Max Transfer Supply
Type Size (mm) Weight (g)
Rate (SPI) Voltage
SD 32 x 24 x 2.1 2 25 Mbit/sec 3.3
mini SD 21.5 x 1.4 0.8 50 Mbit/sec 3.3
micro SD 11 x 15 x 1 0.25 50 Mbit/sec 3.3

10. Rechargeable Batteries
Type Output Capacity Size (mm) Price
50.8 x 33.5 x
Lithium Ion 3.7 V 1000 mAh 11.00
5.9
Ni-Cd AA 1.2 V 1200 mAh 50 x 10.5 dia. 1.55
Ni-MH AA 1.2 V 2500 mAh 50 x 10.5 dia. 3.99
http://www.batteryspace.com

11. Bluetooth Module
• For future works, connection to smart
phones will be easier with Bluetooth
• Adds usability, convenience, and ease-of-use
• Range is not an issue
• Buying a module is faster than designing my own PCB
• flash, crystal, filters, antenna, and amplifiers included in RN-42

12. Bluetooth
WT12 WT41 WT21 RN-41 RN-42
TX POWER 3 dBm 19 dBm 7 dBm 15 dBm 4 dBm
CLASS 2 1 1.5 1 2
RANGE 30m 500-1000m 100-200m 100m Max 20m
OP. VOLT 3.3 3.3 1.8-3.6 3.3 2.7-3.0
Sleep
Mode
1 mA 3.0 mA 1.5 mA 2.5 mA 0.026 mA
Power 2 mW 79 mW 5 mW 31.6 mW 2.5 mW
SIZE (mm) 26x14x2.4 35x14x3.5 17x11x2.6 19x13.4x2 13.4x26x2

13. Software Hardware
• Microchp’s MPLAB IDE • Bluetooth Module
• C++ • Micro SD card
• Microcontroller programming
• USB
• Python version 2.6
• Battery
• Computer
• MCU
• Bluez
• Accelerometer
• Eagle
• PCB Design

14. Experimental Results
• Accelerometer interfacing with microcontroller
• Save to SD Card
• Bluetooth file transfer established between smart phone
and computer using Linux

15. Risks & Challenges
• Bluetooth implementation
• Minimizing size and power consumption
• Perfecting the Fall Detection Algorithm
• Designing the PCB with Eagle
• Working with a 32-bit MCU

16. EE Courses
• Microcontrollers – ES 310
• Electronics – ES 330/230
• Wireless Communications – ES 485-03
• Intro to Antenna Theory – ES 485-01
• Analog and Digital Communications – ES 442
• Electromagnetic Theory – ES 430

17. Preliminary Costs
• Uno32 Chipkit
• ADXL345 Breakout Board

18. Bill of Materials
Item Cost Acquired
MCU $5.17 NO
ADXL345 Accelerometer $14.95 NO
RN-42 Evaluation Board $40.00 NO
SanDisk micro SD $4.00 NO
micro SD Socket $3.95 NO
Lithium Ion Battery $11.95 NO
USB Connector $1.20 NO
USB LiPoly Charger $14.95 NO
PCB $169.00 NO
RN-240M $59.00 NO
TOTAL $324.17

19. Schedule
MCU Programming
Environment Ready
Fall Detection
Complete Bluetooth
Save Data on Works
SD Card
Assemble Box

20. References
• Microchip website: http://www.microchip.com
• Dr. Farahmand’s website:
http://www.sonoma.edu/users/f/farahman/
• SD Group Technical Committee, SD Card Specifications:
Physical Layer, Version 3.01

21. Advisors
• Project Advisor: Professor Jack Ou
• Industry Mentor:

22. Questions?
• www.benvaldo.com/senior-project-blog

23. Basic Data Packet
Access Code Header Payload
Preamb Sync Trailer AM_ADDR TYPE FLOW ARQN SEQN HEC DATA
le Word
4 64 4 3 4 1 1 1 8 0-XXX
Accelerometer Data Payload
Header Board ID # Time Event
8 8 64 8

24. Accelerometer

25. Accelerometer fall detection
• 8 interrupts
DATA_READY, SINGLE_TAP,
DOUBLE_TAP, ACTIVITY,
INACTIVITY, FREE_FALL,
WATERMARK, and OVERRUN
• Algorithm
• Determine the start of the fall
• Detect impact, which has
largest impact
• Aftermath: body doesn’t rise
immediately
• Comparing orientation
before and after.

26. Algorithm

27. RTCC
• 24-Hour Format (Military Time)
• Visibility of One-Half-Second Period
• Provides Calendar: Weekday, Date, Month and Year
• Alarm Intervals are configurable for Half of a Second, One
Second, 10 Seconds, One Minute, 10 Minutes, One Hour,
One Day, One Week, One Month and One Year
• Alarm Repeat with Decrementing

28. SD card specifics
• Initial communication through synchronous one-bit
interface
• Host provides clock signal and can command card to
use different operating voltage
• Host prepares card for read/write of data block
• SDHC and SDXC cards can operate at 1.8-volt
• Formatting
• For SDSC cards: FAT16
• For SDHC cards: FAT32
• Power use 66-330mW (20-100mA) @ 3.3-V
• Max transfer of 50-Mbit/sec

29. Function boards
• Power, Ground, and various I/O ports
• Will be encased inside box
• Automatically identified by microcontroller

30. Microcontroller
• PIC32MX320F128H
• 128K Flash Memory, 128 KB Program Memory
• Processing power needed for Fall Detection
• 2 internal oscillators
• 2 SPI, 2 I2C
• 16 ADC Channels, 85 I/O Pins
• Other Microchip 32-bit MCU’s are viable option
• Much room for further project development