ECE 477
Digital Systems Senior Design Project
Rev 8/12
Homework 3: Design Constraint Analysis and Component Selection Rationale
Team Code Name: TableGames Unlimited
Group No. 8
Team Member Completing This Homework: Justin Pancake
E-mail Address of Team Member: jpancake@purdue.edu
NOTE: This is the first in a series of four “professional component” homework assignments,
each of which is to be completed by one team member. The body of the report should be 3-5
pages, not including this cover page, references, attachments or appendices.
Evaluation:
SEC
DESCRIPTION
1.0
Introduction (including updated PSSC)
2.0
Design Constraint Analysis
MAX
10
-
2.1
Computational Requirements
10
2.2
Interface Requirements
5
2.3
On-Chip Peripheral Requirements
10
2.4
Off-Chip Peripheral Requirements
5
2.5
Power Constraints
5
2.6
Packaging Constraints
5
2.7
Cost Constraints
5
3.0
Component Selection Rationale
20
4.0
Summary
5
5.0
List of References
10
App A
Parts List Spreadsheet
5
App B
Updated Block Diagram
5
TOTAL
Comments:
Comments from the grader will be inserted here.
100
SCORE
ECE 477
Digital Systems Senior Design Project
Rev 8/12
1.0 Introduction
The proposed project is a virtual interactive tabletop game surface that will recognize user
input in the form of multi-touch gestures as well as identifying and tracking unique game pieces.
The intended application of this project is to provide a platform for one or many users to play
games in an immersive touchscreen oriented environment. Some of the main design constraints
of this project are responding to user input with as little latency as possible, the cost of the
overall product, and the size of the final package.
Updated PSSCs:
1. An ability to control fan speed as a function of operating temperature. (MC)
2. An ability to recognize touchscreen inputs via infrared image processing. (MOBO)
3. An ability to recognize and track unique game piece position and orientation via fiducial
pattern tracking. (MOBO)
4. An ability to control projector settings such as brightness, contrast, and focus via IR
communication. (MC)
5. An ability to generate sound effects coordinated with the game being played. (MC)
2.0 Design Constraint Analysis
As mentioned in the introduction, the major design constraints of this project are as follows:

Cost: The project should be made as low cost as possible to make it both accessible
and a competitive choice against other gaming platforms available to the consumer.

Packaging Size: The project needs to be both large enough to emulate the physical
board games it is intended to replace, as well as portable enough to be convenient to
the user.

Computation Speed: The project needs to analyze and recognize user input and
respond appropriately in real time, with as little latency as possible.

Heat Dissipation: All project components will be housed in an enclosed
compartment beneath the tabletop surface. With many computation components as
well as the projector running, a significant amount of heat will be generated,
requiring an active fan cooling system to manage the heat.
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ECE 477
Digital Systems Senior Design Project
Rev 8/12
2.1 Computation Requirements
The major computational requirement of this project is to identify and respond to user input
as quickly as possible. All activity on the tabletop surface will be captured via an infrared
camera and processed via the open source visual processing framework reactTIVision. This part
of the computation will be performed on a motherboard with a desktop processor, as existing
microcontrollers and processor families such as the Intel Atom are insufficiently powerful for
this task. In addition to running the reactTIVision software, the motherboard will also be
running a minimal Ubuntu Linux distribution, as well as handling the graphics and game logic
for all games played. The requirements for each of these computational loads are summarized as
follows:
reactTIVision[5]:
Ubuntu Linux[6]:
-2 GHz Intel Processor.
-700 MHz Processor
-2 GiB RAM
-512 MiB RAM
-2 GiB HDD
-5 GiB HDD
The computation requirements for the game logic and graphics are not listed because they
are trivial when compared to the requirements set forth by reacTIVision and the Ubuntu
operating system. That being said, any motherboard and processor chosen that can support
reactTIVision will be able to easily handle any games we implement as well as Ubuntu.
The microcontroller in this project will also be in charge of a decent amount of
computation. The controller will be handling all sound associated with the games being played as
well as managing all project peripherals, which include fans, speakers, and IR transmitters and
receivers. In comparison to playing music, all other tasks delegated to the microcontroller are
trivially easy, and in most cases, are simply on/off toggling. The microcontroller will also need
to possess a large amount of flash memory in order to store sound files, or be able to connect to
an external storage device, such as an SD card, to play the sound files. As for the clock speed of
the controller, it has been determined that a clock speed of 32MHz will be more than sufficient to
playback sound files as well as all other interfacing and peripheral management that needs to be
done.
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ECE 477
Digital Systems Senior Design Project
Rev 8/12
2.2 Interface Requirements
The microcontroller will need to interface with various off chip devices via GPI/O pins.
The controller will be controlling an IR transmitter and toggling power for IR lamps via its
GPI/O pins. The IR transmitter will require a single GPI/O pin and is controlled like any other
LED, with a 5V output signal and a current limiting resistor. The IR lamps will be powered by an
external power supply, but will be toggled off and on by the controller. This will also take a
single GPI/O pin and the IR lamps will be optically isolated from the controller outputs. In
summary, a tentative minimum of two GPI/O pins will be required on the controller.
2.3 On-Chip Peripheral Requirements
The interface requirements of the motherboard are relatively simple. The motherboard needs
to be able to communicate with the IR camera via USB, drive the projector via VGA output, and
coordinate with the microcontroller via a serial interface. Meeting these requirements on the
motherboard will be trivial, as VGA, USB, and serial I/O are standard features on the vast
majority of modern motherboards.
The on chip peripheral requirements of the microcontroller are more numerous. The
controller needs to interface and communicate with a number of off chip devices. An RS-232
UART interface is required to coordinate with the motherboard; ATD channels are required to
read input from temperature sensors; PWM channels to drive speakers and control fan speed; an
SPI channel with which to interface with an external SD card. In summary, the minimum
peripheral requirements are summarized below for each the controller and the motherboard.
Motherboard:
Microcontroller:
-1x VGA Output
-1x 10-bit ATD Channel
-2x USB
-4x 8-bit PWM Channels
-1x Serial Port (RS-232)
-1x UART (RS-232) Channel
-1x SPI Channel
2.4 Off-Chip Peripheral Requirements
The only off chip requirements as of now are in the projector and the IR camera. The
projector must be able to accept VGA input as a source of video, and the camera must be able to
output its video feed via USB.
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ECE 477
Digital Systems Senior Design Project
Rev 8/12
2.5 Power Constraints
This project will be running a projector and a motherboard with a desktop class processor
at all times while the device is powered on, which will consume a significant amount of power.
Since this project is not battery powered or meant to be mobile while in use, minimizing power
draw is not the main focus. The table will be powered by a single AC power input, which will
then be used to drive the motherboard power supply, projector, PCB, IR Lamps, and cooling
fans.
While power consumption is not a major concern for the constraints of this project, the
heat dissipation is. All components, including the projector, will be running in an enclosed
compartment beneath the tabletop. This will cause the compartment to heat up very quickly and
can cause improper functioning, ie, most projectors will automatically shut off if a certain
temperature threshold is reached. To combat this, a series of fans will be installed in the sides of
the enclosure to pull and push air out of the box and maintain a suitable temperature level.
2.6 Packaging Constraints
The main packaging constraints associated with this project are the height of the tabletop
surface, which will dictate the required throw distance of the projector and the focal length of the
camera lens. The surface needs to be large enough to emulate traditional board games as well as
be high enough for users to comfortably sit or stand while using the tabletop surface.
2.7 Cost Constraints
This project aims to compete with existing commercial tabletop touch surfaces such as
the Microsoft Table and the Reactable, which are linked in the references section. Both the
Microsoft Table and Reactable are products that use comparable technology and have similar
targeted applications. Both are tabletop surfaces and interact with users via touch interfaces.
The Reactable has an MSRP $8100[3] and the Microsoft Table has an MSRP $8400[4].
Our project aims to compete with these products by providing a comparable experience at
a fraction of the price. Since our project requires components that scale rapidly in price with
quality, such as projectors, the estimated cost constraint target of this product is $750. This price
would include all components and the assembly of the final product.
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ECE 477
Digital Systems Senior Design Project
Rev 8/12
3.0 Component Selection Rationale
Projector/Camera: The major components that will be compared are the motherboard/cpu
and the microcontroller. The projector and camera are also integral pieces of the project,
however, aside from cost, they have no special criteria that warrants detailed comparisons. The
camera needs only to be able to see in the IR spectrum, ie, virtually any IR camera with a USB
interface is suitable with this project. The same reasoning applies to the projector choice; it needs
only to be a Short Throw projector, as there will be a short distance between the projection
surface and the projector itself.
CPU/Motherboard: When considering the requirements for the reacTIVision framework
and the other tasks the motherboard would be performing, it was determined that an embedded
Atom board solution would not be able to comfortably handle the projected load. As such, it was
decided that an entry level desktop processor would be used in conjunction with a micro-ATX
form factor motherboard.
Initial testing of the ReacTIVision software with an older laptop showed a CPU utilization
of roughly 25% for the ReacTIVision processes. Allowing for other processing to happen on the
motherboard, a 25% CPU utilization is used as a target for this design. With this test as a
benchmark, it was determined that virtually any current generation entry level processor would
be sufficient for this project, leaving only cost as a constraining factor. The motherboard needs
only to be micro-ATX form factor, as size is a concern, and the other requirements, such as VGA
output and USB ports, are standard features on all modern motherboards, and a detailed
comparison between boards is not needed.
Microcontroller: Using the on chip peripheral requirements listed above in section 2.3,
two microcontrollers were compared for this project, as shown below:
Model
CPU
I/O
UART
ADC
PWM
Flash
Package
Price
ATxmega128A4U[1]
8/16
bit
32
MHz
34
7
12@
12b
16@
16b
128kB
44 Pin
TFQP
$4.40
PIC24F16KM202[2]
16-bit
32
MHz
24
2
19@
12b
5@
16b
16kB
28 Pin
SPDIP
$3.05
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ECE 477
Digital Systems Senior Design Project
Rev 8/12
As the chart shows, both microcontrollers meet the minimum peripheral and computational requirements.
For this project, the Atmel Mega chip was chosen because it offers more room for possible expansion as
well larger amounts of flash memory and internal registers for ease of development and program
efficiency. Though the Atmel chip is larger and costs more per unit, the benefits it offers over the PIC
chip are significant enough to justify its choice.
4.0 Summary
In summation, the proposed project is constrained mostly by cost and in some cases, the
limitations of the packaging design. The intended functionality of the design relies on being able
to process and react to user input with as little latency as possible, and it was deemed the Atom
family of embedded processors lacked sufficient computational power to achieve this. The class
of processor and motherboard chosen for this project easily meet and exceed all computational
requirements set forth by the reacTIVision framework and Ubuntu Linux operating system, and
are therefore only constrained by cost and the micro-ATX form factor. The microcontroller
chosen meets all peripheral requirements, while leaving room for expansion, and fits with the
common low cost constraint being applied to all component choices.
The final constraints considered in this report are the packaging, power and heat
considerations. Since all project components must fit into an enclosure beneath the table top
surface, minimizing physical footprint is a primary goal. Since many components are running in
a small enclosed space, heat is a very real concern and an active fan cooling system will be
required to keep temperature levels at an acceptable level. As this device is not mobile or
intended to run off of batteries, power is not a constraining factor.
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ECE 477
Digital Systems Senior Design Project
Rev 8/12
5.0 List of References
[1] “ATXMEGA128A4U-AU Atmel.” Internet: http://www.digikey.com/productdetail/en/ATXMEGA128A4U-AU/ATXMEGA128A4U-AU-ND/3441468, [Sep. 13, 2013].
[2] “PIC24F16KM202 SO Microchip Technologies.” Internet: http://www.digikey.com/productdetail/en/PIC24F16KM202-I%2FSO/PIC24F16KM202-I%2FSO-ND/3872769, [Sep. 13, 2013].
[3]
“Reactable.” Internet: http://www.reactable.com/products/live/order/, [Sep. 13, 2013].
[4]
“Samsung LFD Monitors.” Internet:
http://www.samsunglfd.com/solution/app.do?modelCd=Surface, [Sep. 13, 2013].
[5]
“System Requirements.” Internet:
http://wiki.nuigroup.com/Getting_Started_with_tbeta#System_Requirements, [Sep. 13,
2013].
[6]
“Installation/System Requirements.” Internet:
https://help.ubuntu.com/community/Installation/SystemRequirements, [Sep. 13, 2013].
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ECE 477
Digital Systems Senior Design Project
8/12
Appendix A: Parts List Spreadsheet
Vendor
Digi-Key
Newegg
Newegg
Newegg
Environmental
Lights
Environmental
Lights
Newegg
Newegg
Digi-Key
Mouser
Staples
Manufacturer
Atmel
Athena Power
AMD/BIOSTAR
G.SKILL
Environmental
Lights
Environmental
Lights
SanDisk
Cooler Master
Analog Devices
LITEON
Optoma
Part No.
AP-MP4ATX30
A4-3300/A75MG
F3-10600CL9D-4GBNS
IR850
Description
16-bit microcontroller
Micro-ATX power supply
CPU/Micro-ATX motherboard Combo
DDR3 SDRAM for motherboard
USB IR Web Camera
IR12-850-quad
850nm IR lighting kit
128.50
1
$128.50
SDCZ80-016G-A75
R4-L2S-122B-GP
TMP36GT9Z
LTE-302-M
DS325
16GB USB 3.0 Flash Drive
2x 120mm Case Fan
Temperature Sensor IC
IR Emitter
Multimedia SVGA Projector
29.99
10.99
1.42
0.22
299.99
1
1
1
1
1
$29.99
$10.99
$1.42
$0.22
$299.99
ATxmega128A4U
Unit Cost Qty
4.40
1
39.99
1
69.98
1
36.96
1
85.00
1
TOTAL
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Total Cost
$4.40
$39.99
$69.98
$36.96
$85.00
$707.44
ECE 477
Digital Systems Senior Design Project
Appendix B: Updated Block Diagram
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8/12