Programming Project

CSE 230 Project 3: UART Palindrome Checker

Learning Objectives:

● Create modular code and interface with unfamiliar modularized code

The Task

In this project, you will be writing a program that receives a string of characters via the UART, checks if this

string is a palindrome, and then uses a print function to print either “Yes” or “No”. A palindrome is a sequence

of characters (typically a word or phrase) that is the same both forwards and backwards. For this project, strings

will be terminated using a period (‘.’). You may assume that a string will contain at least one letter in addition to

a period (e.g., the input, “b.”, should be considered a palindrome). You will not need to handle empty strings,

strings containing only a period, or stings containing characters other than letters, spaces, and periods. Your

program should be able to handle multiple strings sent one after another or concatenated together. For

example, the string: “abba. data.” should print “Yes” followed by “No” on the next line. Spaces should be

ignored when checking for a palindrome and the palindrome should not be case sensitive. For example, “A nut

for a jar of Tuna.” would be considered a palindrome.

Print Function

A template PLP project file is available to download on Canvas. The PLP project includes a second ASM file titled,

project3_lib.asm. This ASM file contains the print function used in this project. PLPTool concatenates all ASM

files within a PLP project into a single location in memory (unless additional .org statements have been added to

specify different location for code). No changes to project3_lib.asm should be made.

When called, depending on the value in register $a0, the following string will be displayed on the simulated

UART device’s output. If $a0 contains a zero then “No” will be displayed and if $a0 contains a non-zero value

(e.g. one) then “Yes” will be displayed. The print function is called using the following instruction:

call project3_print

To use the print function, your PLP program needs to initialize the stack pointer ($sp) before performing the

function call (or any other operations involving the stack pointer). For this reason, the template project file

includes an initialization that sets the stack pointer to 0x10fffffc (the last address of RAM).

Template Structure

The template project file contains six function stubs that need to be implemented. Five are called from the main

loop and the sixth is called from “period_check”. The template file contains comments with descriptions of what

each function needs to do and how it should be implemented. The table below provides a brief description of

the functions.

Function Name Function Description

poll_UART

Polling loop for UART’s status register,

reading new character, and indicating

character has been read

period_check

Checks if new character is a period and

makes a nested function call to

palindrome_check if it is

space_check Skips saving space characters to array

case_check
Converts new character to uppercase if it is

lowercase

array_push Saves new character to array

palindrome_check

Moves inwards from front and back of array

and compares characters at each step to

determine if the string is a palindrome. If at

any point mirroring characters are not

equal, then it should use the print function

to print “No”. If the comparison reaches or

passes the midpoint then the print function

should be used to print “Yes”.

Debugging Tools

To show that you properly tested your program, please save your program while it is in simulation mode (the

blue simulation mode button has been toggled on) such that a CPU Memory Visualization window is open and

shows at least the first 6 words of memory in the array. Please keep in mind that the starting address of the

array is relative to the number of initializations placed before the assembler directive allocating space for the

array. If you change your initializations you may need to adjust your CPU Memory Visualization base address.

The Array Example video in this project’s module demonstrates how to set up a CPU Memory Visualization

window. It is acceptable to also see program contents in memory (these cells will be colored blue). For example,

it would be acceptable to see the following in the visualizer after the string, “abcd.”, has been sent by the user.

Additionally, the watcher window should contain, at minimum, registers $v0, $s1, and $s2. You may also include

any other registers in the watcher window that you find useful for debugging.

Points will be deducted if a CPU Memory Visualization window configured to show the start of the array does

not open when simulation mode is toggled on or the watcher window does not include the minimum set of

registers (the watcher window does not need to open when simulation mode is toggled on).

Deliverables:

1. Take the Project 3 Pre Quiz (6 points)

2. Submit your program on Canvas with the format: Firstname_Lastname_project3.plp (21 points)

3. Take the Project 3 Post Quiz (3 point)