Engineering H192 - Computer Programming
Software Design Project
Lecture 29
Winter Quarter
Gateway Engineering Education Coalition
Lect 29
P. 1
Engineering H192 - Computer Programming
ENG H192 Software Design Project
• Problem: Detect frequency of IR transmitter
• Two-person teams will -– Design
– Code
– Test
– Document
• Teams will be provided -– Handy Board
– Sharp GP1U5 IR receiver
– Access to IR transmitter beacon
Winter Quarter
Gateway Engineering Education Coalition
Lect 29
P. 2
Engineering H192 - Computer Programming
The Handy Board
Winter Quarter
Gateway Engineering Education Coalition
Lect 29
P. 3
Engineering H192 - Computer Programming
The Sharp GP1U5 IR Receiver
Winter Quarter
Gateway Engineering Education Coalition
Lect 29
P. 4
Engineering H192 - Computer Programming
General Description
• Your software must detect each of five (5)
possible frequencies of transmitted IR light
• Frequency detected must be displayed on Handy
Board LCD screen
• Frequencies will in the range of 20 to 150 Hz
• No frequency will be closer than 20 Hz to any
other possible frequency
• Transmitted frequency will change automatically
and randomly to one of the other possible
frequencies
Winter Quarter
Gateway Engineering Education Coalition
Lect 29
P. 5
Engineering H192 - Computer Programming
IR Transmission and Reception
• Program should continuously detect frequency of
the transmitting beacon
• Handy Board screen should display received
frequency in Hertz as an "integer" value
• Only one of the specified frequencies (or 0) should
be displayed
6 to 12 inches
IR Receiver
Winter Quarter
IR Transmitter
Gateway Engineering Education Coalition
Lect 29
P. 6
Engineering H192 - Computer Programming
The IR Beacon Signal
IR Beacon Signal
X
X
X
X
X
X
X
0
X
1
X
X
X
X
X
X
X
X
X
X
X
X
"Digitized" copy of signal
Time
Winter Quarter
Gateway Engineering Education Coalition
Lect 29
P. 7
Engineering H192 - Computer Programming
A Possible Approach
• Take a number of measurements of the received
signal at regular intervals
• Determine how long it took to take those
measurements
• Analyze set of measurements
• Display appropriate frequency
• Repeat
Winter Quarter
Gateway Engineering Education Coalition
Lect 29
P. 8
Engineering H192 - Computer Programming
Useful Handy Board Functions
• digital (p) -- Returns the value of the sensor
connected to digital port "p" as a true/false value.
– The parameter "p" should be in the range of 7
through 15, matching port to which receiver is
connected
– Note that "true" = zero volts, which is
sometimes called "active low"
• start_button ( ) -- Returns the value of the start
button. "True" when button is pressed.
Winter Quarter
Gateway Engineering Education Coalition
Lect 29
P. 9
Engineering H192 - Computer Programming
Useful Handy Board Functions
• stop_button ( ) -- Returns the value of the stop
button. "True" when button is pressed.
• mseconds ( ) -- Returns a long integer value
representing the system time in milliseconds.
– Like the seconds ( ) function, but data type of
returned value is long & units are milliseconds
• reset_system_time ( ) -- Resets the count of
system time to zero milliseconds.
Winter Quarter
Gateway Engineering Education Coalition
Lect 29
P. 10
Engineering H192 - Computer Programming
Interactive C
• Remember, there are things that are different in
IC (compared to ANSI C):
– No function prototypes
– Limited formats possible in printf
– Array bounds checked at run time
– No #include statements
– Smaller set of allowable data types -- only int,
long, float, char, and struct (v3.2 only)
– Character strings are supported, but simple
char variables are not
Winter Quarter
Gateway Engineering Education Coalition
Lect 29
P. 11
Engineering H192 - Computer Programming
Interactive C
• More things that are different in IC (compared to
ANSI C):
– No switch/case construct
– Can only do +, -, and * on long int
– All source files must be compiled together
– #define has global scope
– User functions come first in source file
– No do/while construct
– No mixed mode arithmetic
Winter Quarter
Gateway Engineering Education Coalition
Lect 29
P. 12
Engineering H192 - Computer Programming
Design Project "Deliverables"
• List of brainstorming ideas
• Neatly written algorithm and/or flow chart of userwritten functions
• Documentation package which includes:
– A description of the program for use by
developers, complete with a list of variable
names and uses
– A description of the program for use by a
general user with an abstracted discussion of
the program.
Winter Quarter
Gateway Engineering Education Coalition
Lect 29
P. 13
Engineering H192 - Computer Programming
Receiving in a "Noisy" World
• Real world communications are affected or
"degraded" by noise, for example:
– Normal conversations in a busy public place
– Cell phones in fringe reception areas ("Can
you hear me now?"™)
– AM radio stations during thunderstorms
• Often measured as a "signal-to-noise" ratio which
is usually called SNR
• Almost all forms of communication are range
dependent -- longer range => lower SNR
Winter Quarter
Gateway Engineering Education Coalition
Lect 29
P. 14
Engineering H192 - Computer Programming
Receiving in a "Noisy" World
• The IR transmitter and receiver system we are
using is "range dependent"
– How does light intensity vary as a function of
distance?
• IR receiver "drops out" if transmitted signal is too
weak
– What does "drops out" mean?
• Can we improve our ability to "see"?
Winter Quarter
Gateway Engineering Education Coalition
Lect 29
P. 15
Engineering H192 - Computer Programming
The "Noisy" IR Beacon Signal
IR Beacon Signal
1
0
X
X
X X X
X
X X X
X
X
X
X
X
X
X X X
X
X
X
X X X
X
"Digitized" copy of signal
Time
Winter Quarter
Gateway Engineering Education Coalition
Lect 29
P. 16
Engineering H192 - Computer Programming
A Possible "Noisy" Approach
• Take a number of measurements of the received
signal at regular intervals
• Determine how long it took to take those
measurements
• Analyze set of measurements and ignore periods
that are shorter than average
• Compare results of several sets (Steps 1 - 3)
• Display appropriate frequency
• Repeat from beginning
Winter Quarter
Gateway Engineering Education Coalition
Lect 29
P. 17
Engineering H192 - Computer Programming
Possible Programming Pitfalls
• Failing to use global variables, particularly for
medium or large arrays
• Scarcity of comments in code (comments don’t
take any memory space)
• Improper use of Handy Board functions
• Not using modular approach to designing code
• Too much floating point arithmetic
• Too much code – exceed memory of Handy Board
Winter Quarter
Gateway Engineering Education Coalition
Lect 29
P. 18