Assignment #3 Solution

This assignment has three parts:







Written Part: A small written part is available on the Connex site: Tests&Quizzes.



Programming Part: Will be submitted via the Assignments link on the Connex site.



Demonstration: You will be required to demonstrate the functioning of the programming part of your assignment to a member of the teaching team. Demos after the week of November 14 in the labs.






Objectives

Gain confidence with assembly language programming.



Create effective subroutines/functions.



Use peripherals: the LCD



Become familiar with the use of busy-waiting



Academic Integrity




Prior to submitting your assignment, carefully read the University policy on Academic Integrity:

http://web.uvic.ca/calendar2014/FACS/UnIn/UARe/PoAcI.html




If you do not understand the meaning of anything in the document, please ask. A plagiarism detection tool is used on assignment submissions.










Assignment 3: Programming Part [50]







The LCD




The boards we are using have a Hitachi HD44780 compatible LCD display that has its own (simple) processor. To communicate with that processor a specific protocol is used that initializes and controls the LCD screen. Learn more about how the LCD controller works by looking at the data sheet: https://www.sparkfun.com/datasheets/LCD/HD44780.pdf




A previous CSC 230 student has written a library of subroutines for this assignment. The table below lists the subroutines, their parameters and what they do.




There is an example program that shows how to use the LCD functions in the file:




lcd_example.asm. Review the files, searching for a way to set the number of rows on the LCD to 2 and the number of columns to 20.




LCD Moving Message Sign




LCD advertising signs often move written messages on a screen and flash. The movement and the flashing are very effective at attracting attention. The goal of this programming task will be to display alternately two written messages, gradually moving them down and across the screen, and to display and flash both messages. Please name this file as “display.asm” for submission on connex.




In particular, the program will need to:




Create two messages that will be displayed on the screen. For example, assume: msg1 = "YourName"



msg2 = "CSC 230: Fall 2016"




When the program starts, the LCD screen will contain: YourName in the first row of the
screen and CSC 230: Fall 2016 in the second row.




After approximately one second, the LCD screen will be cleared then will be set to contain: YourName with the Y in the first column of the first line of the screen. After approximately one second, the LCD screen will be updated and the first message



replaced in the same location with: “CSC 230: Fall 2016” with nothing displayed on second line.







After another one second, the LCD screen will be cleared then will be set to contain: YourName with the Y in the second column and on the second line of the screen. After



approximately one second, the LCD screen will be updated and the previous message replaced (in the same location) CSC 230: Fall 2016




After the message has been displayed clear the screen, wait one second, then repeat all of the above steps 2 more times.
Finally, clear the screen, then set the screen to flash (turn on and off) four *s,
‘****’ at the center of the screen on both lines.




Implementation Help




The instructor's solution has the following in the data segment:




sample strings



These are in program memory msg1_p: .db "YourName", 0
msg2_p: .db "CSC 230: Fall 2016”, 0




.dseg




;




The program copies the strings from program memory



into data memory.
;




msg1: .byte 200

msg2: .byte 200

These strings contain the 16 characters to be displayed on the LCD



Each time through, the 16 characters are copied into these memory locations line1: .byte 17



line2: .byte 17




With these data definitions, the main loop of the application looks like:




initialize the lcd




clear the lcd




copy the strings from program to data memory do 3 times:

set row counter to 0 and column counter to 0




display line1

display line2

delay 1 second

do 2 times:




clear the lcd

display line1

delay 1 second




display line2

delay 1 second




increment row and column counters clear the lcd

flash “**”at centre of screen on both lines




You should make extensive use of subroutines in your code. In fact, each line above is its own subroutine. Including the delay code (which you can borrow from your lab) the solution is ~300 lines of assembly language. Start now!




Extending the Moving Message Sign




Now it is time to add some features. Here are some options. You can choose any one of them.

Extend the application so that you can press the “UP” button to stop the display. If




stopped, pressing the “DOWN” button will restart the sign.

Add another improvement, here are some suggestions:




Allow button presses to increase and decrease the sign change speed
o Allow the user to select different messages

Implement a scrolling display for longer messages.




Please name this file as “display_extended.asm” for submission on connex.







In order to handle button presses gracefully you will have to do something other than busy loop waiting, either by checking the buttons in your delay subroutine or by using timer interrupts.




Grading note:




If you submit a program that does not assemble you will receive 0 for that part of the assignment.



If you do not complete a demonstration of your code during the posted demonstration times, you will not receive a grade for this assignment.



The basic moving message sign (as described under the title LCD Moving Message Sign) is worth 80% of the grade for the programming part of the assignment, while the extension (as described under the title extending the Moving Message Sign) is worth 20%.
Please submit your work as “display.asm” and “display_extended.asm” on connex.









Assignment 3: Demonstration Part







At the demo, you will explain how your code works and be asked to make a small change in it.

You will show that you can use the AVR Studio 4 and upload code to the board.




Demonstrations are likely take place during your lab times. If the schedule doesn’t fit in everyone, then some demos may take place outside lab and lecture hours. There will be a sign-up sheet available.



Be prepared to demonstration the functionality of your assignment, to explain how your code works and be asked to make a small change in it. You will need to show competence with AVR Studio 4 and uploading the code to the board.