Assignment 3 Collatz sequence explorer

CSC 230 Assignment 3

Overview
The goal of this assignment is to implement the Collatz sequence explorer. We
have already seen the Collatz sequence in Assignment 1, where we counted the
number of elements in the sequence. To do this, we implemented an algorithm
which computes each value in the sequence and counts how many there are. For
this assignment, in addition to counting them, you are also expected to output
each value and its position (or count) in the sequence on the liquid crystal
display (LCD).
The initial starting value for the sequence will be obtained from the user via the
buttons on the LCD Shield (as described in Specifications below). Upon user
confirmation, the device should display the initial value, whatever it is, and its
count of 0 at the designated locations on LCD. After a short time-delay, the
device will advance to the next value and display its corresponding count of
1. The value and its count will continue advancing with a predetermined timedelay between them until the value reaches 1, at which point the last value
and its count will remain on the screen until the user selects another value.
The time-delay period will be chosen by the user, as described in Specifications
below.
While the Collatz sequence is advancing on the screen, the user should be able
to continue to interact with the input prompt using the LCD shield buttons.
At any time, when the user changes the speed setting, the time-delay should
be adjusted accordingly and immediately. Similarly, when the user changes the
starting value and confirms the selection, immediately upon confirmation, the
sequence display will update with the new starting value and start advancing
from there.
This assignment is composed of several sub-problems that can be completed and
tested separately before combining them into the final solution. This assignment
builds on the previous assignments and labs. You are welcome to use your own
previously written code or the solutions provided to you on conneX during
this course. If you use any of the solutions from conneX, you should reference
them appropriately in the comments. For example, if you copied and modified
the init to string function from Lab 7, then you could say: ”This function is a
modified version of the function int to string from Lab 7, CSC 230, Fall 2019”
in the comments.
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Specifications
• Program start:
When the device starts, or when the reset button is pressed, the LCD
screen should display your first and last name and the phrase ”CSC 230 -
Fall 2019” for a period of 1 second. Then, the screen should change to the
same as shown in the picture below. The cursor should be set to the least
significant digit of the initial Collatz value (“n=”). The speed should be
initialized at 0. The initial Collatz sequence value should be initialized at
0, and its count should be initialized at 0.
• The LCD screen layout:
n = 0 0 0 * S P D : 0
c n t : 0 v : 0
The input fields are highlighted using boldface.
– Top row is designated for prompting the user for the input.
◦ The first three digits (initialized as zeroes), which are next to
the ”n=”, are designated for inputting the new starting value of
the Collatz sequence to be displayed. These digits are updated
one at a time when the cursor is on each of them and the user
presses UP or DOWN buttons on the LCD shield. For example,
if the cursor is on the first of the three digits and that digit is
currently showing as ”5”, pressing UP will change it to ”6”.
This initial starting value could range between 0 and 999.
◦ The asterisk (*) is for confirming the starting value for the new
Collatz sequence. When the cursor is on the asterisk and the
user presses UP or DOWN, the current value and its count
will be updated immediately to the new value and its initial
new count of zero. Then it will continue advancing (or not)
according to the current speed setting.
◦ The last digit (also initialized as zero), which is next to the
”SPD:” is for controlling the amount of time to wait before
advancing to the next value in the given Collatz sequence. This
speed digit is updated when the cursor is on it and the user
presses UP or DOWN in a similar fashion as the first three
digits described above. This speed value could range between 0
and 9.
– Bottom row is designated for displaying the current value and its
count in the given Collatz sequence.
◦ The numbers are periodically updated to the next value and its
count based on a user-determined time-delay.
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◦ The time-delay between advances to the next value is determined by speed value, which is displayed in the first row of the
LCD screen and explained further below.
◦ The maximum possible count could be 3 decimal digits long
and the maximum possible value could be 6 decimal digits long,
hence the corresponding space provided between “0” and “:” on
the second row in the picture above.
Suggestion: Store two strings of length 171
in memory and periodically
update the LCD with those strings (lcd puts function). To change the
message being displayed, update these strings (e.g. via ISR), and not the
LCD, as it will get updated as per previous sentence.
• The cursor:
◦ Since we have several values that can be updated by the user via the
same (shared) set of input controlls (UP and DOWN buttons), we
need some way to indicate specifically which value the user is about
to change. To do that, we keep track which one is currently being
edited and make the corresponding location on the LCD blink. The
blinking effect can be achieved by repeatedly displaying the blank
(space) character for a period of time and then the actual character
that is supposed to be in that location for a period of time.
◦ The user should be able to press the LEFT and RIGHT buttons to
move the cursor between the three digits for the initial Collatz value,
the asterisk, and the sped value. So, 5 possible positions in total. For
example, if the user navigated to the asterisk (*), the asterisk would
blink; then, if a user was to press the RIGHT button, the cursor
would advance to the speed selection and the sped value would start
to blink instead of the asterisk.
• The starting value:
The initial value for the next Collatz sequence to be computed is obtained
from the user.
– Input is in range between 0 and 999 (three decimal digits).
– Provided by the user via the UP and DOWN buttons. Each digit is
updated when the cursor is on that digit (on the LCD).
– Specifies the starting value for the next Collatz sequence.
• The delay/speed:
The frequency at which the new Collatz value is computed and displayed
is obtained from the user.
1. 17 = 16 for each LCD character in one row + 1 for the terminating zero.
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– Input is in range between 0 and 9 (one decimal digit).
– Provided by the user via the UP and DOWN buttons, when the
cursor is on the speed digit (on the LCD).
– Specifies the delay between Collatz sequence value updates:
1 = 1/16 sec. (max. speed of advancing to the next value)
2 = 1/8 sec.
3 = 1/4 sec.
4 = 1/2 sec. ( = 2 Hz)
5 = 1.0 sec. ( = 1 Hz)
6 = 1.5 sec.
7 = 2.0 sec. ( = 0.5 Hz)
8 = 2.5 sec.
9 = 3.0 sec.
0 = full stop (no advancing when speed is 0)
• Limits:
– Max size of Collatz value (“v:”): 3 bytes.
– Max size of Collatz value’s count/position (“cnt:”): 1 byte.
– Decimal range of the displayed value (“v:”): 0-999999.
– Decimal range of the displayed count (“cnt:”): 0-255.
– Decimal range of the speed prompt (“SPD:”) : 0-9.
– Decimal range of the starting value prompt (“n=”): 0-999.
Additional notes and resources
In this assignment you will need to:
• Add 24-bit numbers.
• Display characters on the LCD screen.
• Check which button is pressed on the LCD shield. Both the solution to
Lab 4 and the solution to Assignment 2 have a suitable starting function
that can be modified to work for this assignment.
• Convert between ASCII characters and binary integers that are as large
as 3 bytes (or 224). Lab 7 has a good starting algorithm that needs to be
extended to handle larger values.
• Use at least one timer and interrupts for controlling the frequency at
which the Collatz sequence advances from one value to the next. Lab 8
has a timer-driven interrupt example.
• Online AVR Timer/Counter calculator: https://eleccelerator.com/avr-timercalculator/.
• Online Collatz sequence calculator: https://www.dcode.fr/collatz-conjecture.
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Grading guidelines.
This assignment is worth 9% of your total grade, this value is distributed among
the following categories:
⇒ All functions must protect (back-up or preserve) registers.
3% ⇒ Correct interrupt service routine (ISR). The timing speeds up and slows
down as per specifications. Zero speed results in a complete stop. This
component requires knowledge of interrupts, timers, functions, and register protection.
1% ⇒ At least one function written by you must receive and return a parameter
via the stack. This component requires knowledge of functions and stack.
5% ⇒ User interface. Marks are distributed in various proportions among the
following:
– Credits screen (approximately one second).
– Cursor blinking and moving based on user input.
– Buttons operate as per specifications. Buttons are responsive. Holding down a button doesn’t result in multiple presses being registered.
– Converting binary to ASCII or vice versa.
– Correct Collatz values and counts (on LCD).
BONUS (1% to the total course grade) if your program uses a second ISR and a
separate Timer/Counter for checking the button input, this has a prerequisite
that the buttons operate as per specifications and are responsive, and that
holding a button doesn’t register as multiple presses.
Submission
Submit your solution via conneX. When doing so, verify that your file is actually
uploaded correctly and is not corrupted. You can do so by navigating back to
the Assignments section, then downloading your a3.asm submission (which you
just uploaded), opening it in an editor and visually verifying its contents.
It must be possible to build and run your program on the equipment provided
in the labs (using the same procedure discussed in the lab sessions), otherwise
your solution will not be graded.
The solution is worth 9% of your final grade and must be your individual
work. 
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