EGR 277

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Lecture 4 EGR 262 Fundamental Circuits Lab
EGR 262 Fundamental Circuits Lab Presentation
for Lab 4 Lights and Switches Real Time
Instructor Paul Gordy Office H-115 Phone
822-7175 Email PGordy_at_tcc.edu
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Lecture 4 EGR 262 Fundamental Circuits Lab

• Comments on Lab Notebooks
• After grading Lab 1, a few comments about lab
  reports may be useful
• No loose printed sheets are allowed. Any printed
  sheets must be cut and taped onto lab notebook
  sheets. They must fit within the working area on
  the sheet so that they do not cover the sheet
  number, name, etc.
• Label each section (PreLab, In-Lab, PostLab)
• Add labels/instructions to each item Tell the
  user what you are showing them.
• Include all items listed on the checkoff sheet in
  each section. I will go through the list as I
  grade the labs looking for each item.
• The In-Lab section should be mainly written by
  hand. Take notes and record data in the notebook
  as you work in lab. Remember that the notebook
  is somewhat like a diary, so record every problem
  that you encounter. For example, in Lab 2 did
  you have trouble getting PuTTY to connect? Did
  you record this problem and your solution to it?

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Lecture 4 EGR 262 Fundamental Circuits Lab
Lab 4 Lights and Switches real time Lab 4
involves a modification of Lab 3 where the new
program will count the number of times a button
is pushed in a 10-second interval and then
display that number on a 7-segment display. This
lab particularly shows how a micro-controller can
be used to build systems that control program
execution in real-time. The program in Lab 3
counted the number of times that a button was
pushed after the MicroStamp11 was reset, but the
number of button pushes was not related to time
(i.e., any amount of time could occur between
button pushes). The program in Lab 4 should
count the number of button pushes over a
10-second interval and then stop counting button
pushes. So the program must keep track of the
time deadline as well as count button
pushes. Computer systems whose program
executions satisfy a timed deadline are called
real-time systems. In order to keep track of
time with the MicroStamp11, new kernel functions
are introduced. Switches must also be de-bounced
to keep an accurate count of the button pushes.
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Lecture 4 EGR 262 Fundamental Circuits Lab
Non-real-time systems Programs execute without
any consideration to how long it takes that
program to run.
Real-time systems Program execution is time
sensitive. Some aspect of the computer program
satisfies a time deadline.

• Examples
• Performing mathematical calculations (analyzing a
  circuit, finding moments of inertia, etc.)
• Measuring a voltage and displaying the result
  (i.e., a multimeter circuit).
• Monitoring inputs and responding when certain
  sensors detect inputs (alarm systems, fire
  protection systems, etc).
• Advancing a count on a display every time a
  button is pressed (Lab 3).

• Examples
• Traffic light control system that synchronizes
  traffic lights along some main thoroughfare.
• Car airbag system that must deploy an airbag
  within a critical amount of time.
• Automotive feedback control system (measure
  engine performance and adjust engine operation).
• Display the number of button presses that occur
  in a 10-second interval (Lab 4).

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Lecture 4 EGR 262 Fundamental Circuits Lab
More functions from kernel.c Lab 4 introduces
three important new kernel functions that control
the timing of events.
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Lecture 4 EGR 262 Fundamental Circuits Lab
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Lecture 4 EGR 262 Fundamental Circuits Lab

• 4.1. Pre-lab Tasks
• (1) Write a C-language program (Program 4A - One
  Second Timer) to increment and display a count
  (mod-10) in one-second increments on a 7-segment
  display after a button is pressed. Display the
  count on the terminal program (PuTTY) as well.
  Include the program listing (with many comments).
• (2) Write a description of how Program 4A
  works.
• (3) Write another C-language program (Program 4B
  - Ten Second Button Counter) that counts the
  number of times a button is pushed over a
  10-second interval. Your program should do the
  following
• The timed interval starts with a button push.
• The system will count the number of times the
  button is pushed over a 10 second interval.
• The system should stop the count when the 10
  second time interval has expired.
• The program should display all digits of the
  count on the 7-segment LED display.
• The most signi?cant digit of the count should be
  displayed ?rst and the next signi?cant digit
  should be displayed after a button push (prompt
  the user).
• After all digits have been displayed, the program
  should return to the start and wait for a button
  push to start the next timed interval.
• The count should be displayed on PuTTY as well.
• Give the user clear prompts for all inputs.
• Include the program listing in your notebook
  (with many comments).

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Lecture 4 EGR 262 Fundamental Circuits Lab
4.1. Pre-lab Tasks (continued) (4) Write a
description of how Program 4B works. (5)
Include a schematic diagram breadboard
layout.   The following code segment is a
partial listing for program 4B that you can use
as a starting point. void main(void)init()wh
ile(1) pause(1000) // 1 s pause for
standard mode use 3250 for Turbo
mode button(6) icountcount(6,10000) //
replace 10000 with 32500 for Turbo
mode display_digit(icount)
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Lecture 4 EGR 262 Fundamental Circuits Lab
4.2. In-lab Tasks (1) Compile and download
Program 4A and demonstrate it to the instructor.
Record any changes made to the program. Include
a printout from the terminal program. (2) Use an
online stopwatch program to determine the amount
of time required for your program/circuit to
display 60 counts. Record this time. If the
time is not within 1 second of being correct (60
seconds), adjust the length of pause used in your
program. Make a table showing the values used
with the pause statement and the corresponding
times. (3) Compile and download Program 4B and
demonstrate it to the instructor. Record any
changes made to the program. (4) Experimentally
verify that Program 4B works correctly. Record
(in a table) the number of button presses versus
the displayed value for several cases, including
the following number of button presses 0, 1, 2,
5, 10, 15, 20, 25, and the highest number that
you can press. Include a printout from the
terminal program. (5) Include detailed
handwritten comments (like a diary) of all
activities during lab.   4.3. Post-Lab Tasks
(1) Include a final program listing for each
program. Highlight any changes made to the
original program listing and discuss the changes.
(2) Discuss how well each program performed.