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Project overview
Project-specific success criteria
Block diagram
Component selection rationale
Packaging design
Schematic and theory of operation
PCB layout
Software design/development status
Project completion timeline
Questions / discussion
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Laser tag game system with a few bonuses:
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RF Communication
Designed for outdoor use
Multiple firing modes
Video game style power-ups/shields
Challenges include:
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Long distance IR communication
RF collision and communication protocol
Battery power (especially for high current LED drive)
Packaging to withstand high adrenaline gameplay
Innovative bonus features
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An ability to wirelessly transmit a shot and
receive a hit via Infrared
An ability to remotely enable and disable the
gun/vest pair
An ability to control game operation using
base station keypad
An ability to wirelessly communicate game
statistics to base station via RF
An ability to provide user with local display of
game information
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Microcontroller
◦ Free samples, contains all desired peripherals, well
documented, many GPIO pins
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Radio Frequency
◦ Extremely well documented, phone support, example
prototyping boards, complete solution kit
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Infrared
◦ Based on proven TV remote control technology, sample
schematics available online, inexpensive
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Keypad
◦ Standard, inexpensive 4x4 key array
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LCD
◦ Inexpensive, backlight, low power, wide 2.7-5.5V range
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In Circuit Serial Programmable
48kB Program Memory, 2kB RAM
Internal Oscillator 7.37 MHz
6x PWM for IR transmission
1x SPI for Shift Register/LCD display
4x Input Capture for Keypad and IR detectors
10 bit, 1Msps ATD for RF Signal Strength
2.5 to 5V operating range
72mA max at 3.3V and 20MIPS
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Development kit with example PCBs,
application notes, phone support, and
multiple transceivers and antennas
Receive and transmit within one package
Serial bi-directional communication
Zero configuration
2.6 to 3.6V operating range
Typical supply current: 6-12mA
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Same proven technology from home
entertainment device remotes
TSOP detector filters external sources of IR by
only triggering on 56kHz
Designed for long distance communication
TSAL IR LED rated for 100mA continuous
Vest
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Gun
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PCB Housing
IR Transmitter
LCD Screen
Four Sensor Pods
Status LEDs
Heavy-Duty Fabric
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RF Ground Plane
Durable
LCD Screen
Keypad
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Base Station
◦ Microcontroller
◦ Keypad encoder
◦ Keypad
 Allow user input
◦ Shift Register
◦ LCD Screen
 Displays game stats
◦ RF Transceiver
 Communicates with
gun/vest pairs
Base Microcontroller
External Device
Function
Pin #
Programming Header PGC clock input
1
PGD - data input/output
44
/MCLR - Master Reset
18
VDD
40
VSS
39
Shift Register
SDO1 - SPI Data out
44
SCK1
43
LCD Screen
RE5 - LCD Enable
8
RF0 - Register Select
5
Key Encoder
RE4 - output enable
9
RE3 - Data out D
10
RE2 - Data out C
11
RE1 - Data out B
14
RE0 - Data out A
15
IC7 - Data Available
23
RF Transceiver
AN3 - RSSI
22
RB0 - Data
19
RB1 - T/R Select
20
RB2 -Power down
21
MM74HC164 Shift Register
•8-Bit Serial-in/Parallel-out
•Typical operating frequency:
50MHz
•Typical propagation delay:
19ns (clock to Q)
NHD‐0224BZ‐FL‐GBW LCD
Screen
•2 lines x 24 characters
•Transflective
•Yellow/Green LED backlight
•Potentiometer allows for
change in contrast of screen
•MM74C922 16-Key
Encoder
•Key bounce elimination
with capacitor
•Low power consumption
•On-chip row pull-ups
•Pin 4 – Receive Signal Strength
Indicator
•Pin 7 – Data line will output
received data when in receive
mode and will be a data input
when in transmit mode
•Pin 8 – Transmit and receive
select
•Pin 9 – Power down when low
Gun
• Microcontroller
• Shift Register
• LCD Screen
• Displays game stats
• RF Transceiver
• Communicates with base
station
• IR LED
• Pulses IR signal as a shot
• Laser Diode
• Visual cue to aim
• Trigger
• Batteries
Vest
• Color LEDs
• Simulates the status of the
player and distinguishes
between teams
• IR Receiver
• Receives signal of IR pulse
and sends to gun
microcontroller
Portable Microcontroller
External Device
Programming Header
Shift Register
LCD Screen
RF Transceiver
Trigger
IR LED
Laser LED
Color LED Set 1
Color LED Set 2
Photo Transistor Set 1
Photo Transistor Set 2
Photo Transistor Set 3
Photo Transistor Set 4
Function
Pin #
PGC clock input
1
PGD - data
input/output
44
/MCLR - Master Reset
18
VDD
40
VSS
39
SDO1 - SPI Data out
44
SCK1
43
RE5 - LCD Enable
8
RF0 - Register Select
5
AN3 - RSSI
22
RB0 - Data
19
RB1 - T/R Select
20
RB2 -Power down
21
RF1 - trigger input
4
PWM1H
14
RE2 - Gen I/O
11
RC14 - Gen I/O
35
RE8 - Gen I/O
36
IC1 - input capture
42
IC2 - input capture
37
IC8 - input capture
24
IC7 - input capture
23
Trigger Circuit
• Pin is pulled up in static state
• When button is pressed, switch
pulls pin to ground
• Pin is never floating in this
configuration
• IR LED and laser connected to
PWM to allow for set frequency
pulsing
• NPN transistor as pull-down
• Transistor base connected to
Micro to pulse to allow for larger
drive current
• Pull up resistor to supply voltage
• NPN transistor as pull-down
• Transistor base connected to
microcontroller to pulse to allow for
larger drive current
• Pull up resistor to supply voltage
• Asserts low when 56kHz square
wave pulse is detected; high
otherwise
• Goes to input capture and triggers
a software interrupt on an edge
• Parallel detectors for wider
detection angles
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Considerations:
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RF ground plane
No traces under transceiver
Centrally placed microcontroller
Noise reduction
3” x 5”
3” x 5”
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RF communication protocol: Listen before
transmit with random retry
IR protocol: Simple ID number transmission
like television remote
Practicing with MPLab IDE by Microchip to
create interrupts, run simple programs, and
set up peripheral units
Using MPLab simulator to test chip
functionality before PCB is assembled
Week
Projected Tasks
8
Revise Schematic, Revise PCB, Learn MPLab IDE and Debugger
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Finalize PCB, Ensure all parts are on hand and fit PCB
10
Spring Break
11
RF and IR software communication stacks and protocol
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Game software and remaining software
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PCB Assembly
14
Software and hardware debugging
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Final testing, user manual, demo preparation
16
Final demonstration