1. Software Design Project
Engineering H192
Winter 2005
Software Design Project
Lecture 29
To the Instructor:
The Engineering H192 two person design project is a software design problem.
Two-person teams will design, code, test and document their product.
Winter Quarter
Lecture 29

2. ENG H192 Software Design Project
Engineering H192
Winter 2005
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
To the Instructor:
The Engineering H192 two person design project is a software design problem. Two-person teams will design, code, test and document their product. The "General Description", excerpted from the problem assignment which should be handed out, is as follows:
General Description:
Each two-person team is to design, code, test, and document a software program to detect the frequency of an infrared (IR) transmitting beacon using a Sharp Model GP1U5 IR receiver connected to the Handy Board Controller. The necessary hardware will be provided in class. A modular software design is encouraged. The software design team should develop a user-written function (or package of functions) that will be able to detect each of up to five (5) possible frequencies of IR transmission and display the results on the LCD screen of the Handy Board. The five frequencies will be specified in class.
Winter Quarter
Lecture 29

3. The Handy Board Engineering H192 Winter 2005 To the Instructor:
The hardware platform will be the Handy Board controller, the same controller to be used in ENG H193 to control the robot project in the spring term.
Winter Quarter
Lecture 29

4. The Sharp GP1U5 IR Receiver
Engineering H192
Winter 2005
The Sharp GP1U5 IR Receiver
The Sharp GP15U Infrared receiver is an older receiver used in a variety of application, primarily as the receiver embedded in devices which could be controller via an IR remote (TVs and the like). Here is a wiring diagram for reference only. For this design project, a pre-wired IR receiver is provided.
Winter Quarter
Lecture 29

5. Engineering H192
Winter 2005
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 15 Hz to any other possible frequency
Transmitted frequency will change automatically and randomly to one of the other possible frequencies
To the Instructor:
Here is a general description of the problem.
A test beacon will generate up to five different frequencies of transmitted IR light. The software running on the Handy Board must analyze the signal received by the IR receiver and determine which frequency is being transmitted. The range of possible frequencies is know. The software must be able to track changes in transmitted frequency.
Winter Quarter
Lecture 29

6. IR Transmission and Reception
Engineering H192
Winter 2005
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
Some additional program performance requirements are given on this slide.
IR Receiver
IR Transmitter
6 to 12 inches
Winter Quarter
Lecture 29

7. The IR Beacon Signal IR Beacon Signal 1 "Digitized" copy of signal
Engineering H192
Winter 2005
The IR Beacon Signal
IR Beacon Signal 1
X X X X
X X X X
To The Instructor:
Here is a diagram on which brief explanation of a possible scheme to analyze frequency can be demonstrated. The IR beacon will alternate between "off" and "on". If the software program were to capture a number of samples (uniformly spaced in time) of the received signal and then look for the number of transitions from off-to-on and on-to-off, the frequency being transmitted could be calculated.
X X X X
X X X X
X X X X
"Digitized" copy of signal
Time
Winter Quarter
Lecture 29

8. Engineering H192
Winter 2005
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
To The Instructor:
Here is brief explanation of a possible scheme to analyze frequency. The IR beacon will alternate between "off" and "on". If the software program were to capture a number of samples (uniformly spaced in time) of the received signal and then look for the number of transitions from off-to-on and on-to-off, the frequency being transmitted could be calculated. If this procedure were repeated in a loop, the software should be able to track changes in transmitted frequency.
Winter Quarter
Lecture 29

9. Useful Handy Board Functions
Engineering H192
Winter 2005
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.
To the Instructor:
Some useful functions in the Handy Board support library. The IR receiver should be connected to a digital input port on the handy Board.
Winter Quarter
Lecture 29

10. Useful Handy Board Functions
Engineering H192
Winter 2005
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.
To the Instructor:
More useful functions. Note that "mseconds( );" or "seconds ( );" can be used to measure the elapsed time of a burst of sampling the values detected on a digital input port for example.
Winter Quarter
Lecture 29

11. Engineering H192
Winter 2005
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
To the Instructor:
There are some features of the subset of the C language support by Interactive C of which students should be aware.
Winter Quarter
Lecture 29

12. Interactive C
More things that are different in IC (compared to ANSI C):
Can only do +, -, and * on long integers
All source files must be compiled together or the source file must have “#use” preprocessor commands
#define has global scope
User functions come first in source file
No mixed mode arithmetic
Winter Quarter

13. Design Project "Deliverables"
Engineering H192
Winter 2005
Design Project "Deliverables"
List of brainstorming ideas
Neatly written algorithm and/or flow chart of user-written functions
Documentation package which must include:
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.
To the Instructor:
These are the deliverables of this design project.
Winter Quarter
Lecture 29

14. Receiving in a "Noisy" World
Engineering H192
Winter 2005
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
To the Instructor:
Communications in the real world are affected, sometimes seriously, by noise -- the received signal is almost never is a perfectly clean, pure signal. Signal quality is defined by a metric call Signal-to-Noise ratio, or SNR.
Winter Quarter
Lecture 29

15. Receiving in a "Noisy" World
Engineering H192
Winter 2005
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"?
To the Instructor:
In solving this design problem, students will be challenged to devised ways of improving accuracy in detecting the frequency of the received signal while faced with a noise environment that becomes worse as the distance between the transmitter and receiver is increased. How do you attack this problem?
Winter Quarter
Lecture 29

16. The "Noisy" IR Beacon Signal
Engineering H192
Winter 2005
The "Noisy" IR Beacon Signal
IR Beacon Signal 1
X X X X X X
X X X X X
To the Instructor:
Here's the same diagram as before, now with a "noise" spike in the digitized data.
X X X X X
X X X X
X X X X X
"Digitized" copy of signal
Time
Winter Quarter
Lecture 29

17. A Possible "Noisy" Approach
Engineering H192
Winter 2005
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
To the instructor:
A possible method for accounting for noise in the received data. The key here is ignoring those periods that are shorter than the average period.
Winter Quarter
Lecture 29

18. Possible Programming Pitfalls
Engineering H192
Winter 2005
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
To the Instructor:
Tips and hints for avoiding some troubles with the project.
Winter Quarter
Lecture 29

19. Maximum HB "Sampling" Rates
Engineering H192
Winter 2005
Maximum HB "Sampling" Rates
         Method of input                          Rate (sps)
Analog port with digital( ) function:   530 (ch 2-6)
Digital port with digital( ) function:    430 (ch 10-15) 
570,530 (ch 8,9)
Analog port with analog( ) function:  690 (ch 2-6)
Digital port with analog( ) function:   330 (ch 10-15) 
400,380 (ch 8,9)
Instructor:
Summary of Handy Board sampling rates by port and function.
Winter Quarter
Lecture 29