EC-316 MICROPROCESSOR LAB PROJECT BASED ON INTEL 8085 “SPELL MASTER”

Netaji Subhas Institute of Technology

This is a report of a working project which utilizes Intel 8085 microprocessor. It is a game designed for

children (age groups: 9-13), in which the player has to choose between four similar looking words and

decide which among the four is correctly spelled. As the player advances in the game the score is

incremented with each correct answer. LCD, LEDs and switches are used for the user interface.

Keywords: 8085, students, spell, school, LCD, LED, switches, project, game, score.

SUBMITTED BY:

NIVEDITA SREEJETH (113/EC/13)

PADMA DOLKER (115/EC/13)

ECE-II

TABLE OF CONTENTS

Contents TABLE OF CONTENTS ..................................................................................................................................... 2

ACKNOWLEDGEMENT ................................................................................................................................... 3

INTRODUCTION ............................................................................................................................................. 4

BLOCK DIAGRAM ........................................................................................................................................... 5

SCHEMATIC ................................................................................................................................................... 6

BOARD LAYOUT ............................................................................................................................................. 7

FLOW CHART: ................................................................................................................................................ 8

GANTT CHART: .............................................................................................................................................. 9

GANTT CHART(REVISED): .............................................................................................................................. 9

GIST OF CODE: ............................................................................................................................................. 10

IN THE MAKING: .......................................................................................................................................... 12

HALF SOLDERED: ......................................................................................................................................... 12

FULLY WORKING BOARD: ............................................................................................................................ 13

BILL OF MATERIALS: .................................................................................................................................... 14

TESTING ....................................................................................................................................................... 15

CONCLUSION ............................................................................................................................................... 16

REFERENCES: ............................................................................................................................................... 17

ACKNOWLEDGEMENT

We would like express our deepest gratitude to Prof. Dhananjay V. Gadre for

providing us with this opportunity to learn and grow. The platform that you have

provided has no doubt helped a lot of people .We appreciate your constant support

and guidance which helped us to stay motivated all along.

We would also like to thank our fellow batch mates, who helped us to debug a lot

of things, especially the CEDT members and our parents also.

INTRODUCTION

There are lots of games related to improving one’s ability to know the correct

spelling especially for school going kids. So we thought why not implement it

using microprocessor 8085.

IMPLEMENTATION:

An LCD will display 4 options of similar looking words, from which only one

option would be the correct spelling. There would be one button corresponding to

each option (total four buttons)from which any one can be selected according to

one’s choice .If the correct option is chosen the LCD would display “CORRECT!”

along with the score and a green LED would also glow. If a wrong option is chosen

Then the LCD will display “INCORRECT” without the score being incremented

and a corresponding red LED will glow. After a particular time, the LCD will be

refreshed with next set of words and the game will continue.

BLOCK DIAGRAM

MICROPROCESSOR

8085

ADDRESS

LATCH

MICROPR

OCESSOR

8085

RAM ROM

DECODER

MICROPR

OCESSOR

8085

8255

LCD

MICROPROCESSOR

8085

LED

ULN

DRIVER

DATA BUS

POWER

SUPPLY

SCHEMATIC

BOARD LAYOUT

FLOW CHART:

START

Display “SPELL MASTER” on the LCD

Wait for 1 second.

Display 4 options on the LCD.

Wait for the button press.

Is the button

pressed?

No

Yes

Debounce

Find out which button was pressed

Correct button pressed?

Increment score

Display “CORRECT” and the score on the LCD Display “INCORRECT” and the score on the LCD

Switch on the correct pattern of LEDs (green for the correct one and red for the wrong ones)

Wait for 1 second.

Switch off all the

LEDs

Is it the end of the

game?

NO

Display “END OF GAME” on the LCD

STOP

YES

GANTT CHART:

GANTT CHART(REVISED):

GIST OF CODE:

DELAY of 1 second

WAIT1SEC: PUSH B

PUSH D

PUSH PSW

MVI D,00AH

SECOND: LXI B,04A68H

LOOP3: DCX B

MOV A,B

ORA C

JNZ LOOP3

DCR D

JNZ SECOND

POP PSW

POP D

POP B

RET

CODE FOR DEBOUNCE

KEYCHECK: IN 07FH

ANI 0F0H

CPI 0F0H

JZ KEYCHECK

CALL DEBOUNCE

KEYPUSH: IN 07FH

ANI 0F0H

CPI 0F0H

JNZ OUTFUNC

JMP KEYCHECK

OUTFUNC: PUSH B

PUSH PSW

CMA

MOV B,A

INX H

MOV A, M

CMP B

JZ DSPCRRT ;jump to the subroutine which diplays correct on the lcd

JNZ DSPINC ;jump to the subroutine which diplays incorrect on the lcd

DEBOUNCE: PUSH B

PUSH PSW

LXI B, 041CH ;5MS

LOOP1: DCX B

MOV A,C

ORA B

JNZ LOOP1

POP PSW

POP B

JMP KEYPUSH

IN THE MAKING:

HALF SOLDERED:

FULLY WORKING BOARD:

BILL OF MATERIALS:

Sno Part Package Quantity 1 8085 DIL 40 1

2 8255 DIL 40 1

3 74573 DIL 20 1

4 74138 DIL 16 1

5 ULN2803 DIL 18 1

6 Ceramic

Capacitor

C-EU25-024X044 10

7 Polarized

Capacitor

CPOL-EUES 1

8 LCD 16X2 1

9 LED 3mm 10

10 7404 DIL 14 1

11 Crystal

(4MHz)

HC49US 1

12 Resistors 0207/7 24

13 RAM (32K) 62256 DIL 28

14 ROM (32K) 58256 DIL 28

15 Switches 10XX 6

16 Connectors M10 4

17 Preset (10k) 10P 1

18 Mini USB USB(POWER) 1

TESTING

After making the schematic, first all the errors were identified using ERC tool in EAGLETM. Then board layout was prepared and errors were constantly checked using DRC tool. The board was tested by first checking all the tracks of the PCB, for any cuts in the tracks, merging of 2 or more tracks, followed by the SID SOD testing of the board. A small code was written to light up an LED at the SOD pin every time a switch at SID pin was pressed. This testing made sure that the basic board is functionally correct. LEDs were tested then using a blinking code. Then switches were tested individually, using the LEDs as the output of the switches. Finally the LCD was tested, following proper initialisation. Following were among the few debugging errors that we came across while making the project:-

Incorrect initialisation of the LCD Garbage values were obtained on the LCD upon initialisation, the error being insufficient amount of time given for the LCD to be ready to accept more data from the microprocessor.

Not giving a delay before writing new data onto the LCD Some of the data was not visible to us and seemed to just have skipped out of the whole code. After adding appropriate delays this error was removed.

Not erasing the previous data before printing the new data onto the LCD LCD has to be cleared before printing new data if the new data does not occupy the space consumed by the earlier data!

Incorrect interpretation of the driver IC ULN2803 has an inverting operation because it is an NPN transistor IC.

Confusion between HEX and DECIMAL while writing the code We had to add 10 to a hex number, and instead we added 16 by incrementing the second place number (leading to a garbage value getting displayed on the LCD).

CONCLUSION

Overall this was a good learning expeience in terms of the depth of the knowledge in hardware, software and the basic understanding of the 8085 microprocessor. The working and functionalities of each component used on the board was acquired. A lot of time and effort was given to minute details in the code during testing and debugging. All in all this was a very good experience which made us understand the importance of the applications of the skills acquired and time management for handling each and every task.

REFERENCES:

Microprocessor Architecture, Programming, and Applications with the 8085

by Ramesh Gaonkar, Fifth edition, Penram International Publishing.

ISBN 81-87972-09-2