Contents of Articles

Tests

Test 1
Test 2
Test 3
Test 4
Test 5
Page 19 More to be added here

When you have finished the experiments, go to ”21” a strategy game.

EXPERIMENT 11b

Whistle-On Whistle-Off

This experiment turns on a LED when a whistle is detected. The LED turns off when the whistle is detected for the second time.

     ;Expt11b.asm
     ;Project: Whistle-On  Whistle-Off
List P = 16F84
#include <p16F84.inc>
__CONFIG 1Bh ;_CP_OFF & _PWRTE_ON & _WDT_OFF & _RC_OSC

        ORG 00          ;Start of memory for program.
SetUp   BSF 03,5        ;Go to Bank 1
        CLRF 06         ;Make all port B output
        MOVLW 02        ;Load W with 0000 0010
        MOVWF 05        ;Make RA1 input
        BCF 03,5        ;Go to Bank 0 - the program memory area.
        CLRF 1F         ;Clear flag file
        CLRF 05         ;Clear the display
        CLRF 06         ;Clear the display
        GOTO Main

Delay   NOP             ; Create 1mS delay
        DECFSZ 1A,1
        GOTO Delay
        RETURN

Delay1  MOVLW 40h
        MOVWF 1B
DelayA  DECFSZ 1A,1
        GOTO DelayA
        DECFSZ 1B,1
        GOTO DelayA
        RETURN

Look    BCF 1F,0        ;Clear the "whistle" flag
        MOVLW 040h      ;Number of loops
        MOVWF 0E        ;Loops file
        CLRF 0Ch        ;Holds the LOW count
Look1   CALL Delay
        BTFSC 05,1
        GOTO look2
        INCF 0Ch,1      ;LOW detected
Look2   DECFSZ 0E,1
        GOTO Look1
        MOVLW 18h
        SUBWF 0Ch,0
        BTFSS 03,0      ;Test Carry flag. If set C=more than 10h
        RETURN
        BSF 1F,0        ;Whistle detected
        RETURN

Main    CALL Look
        BTFSS 1F,0
        GOTO Main       ;No whistle
        MOVLW 04        ;Whistle - turn on display
        MOVWF 06
Main1   CALL Delay1
        CALL Look
        BTFSC 1F,0
        GOTO Main1      ;whistle
Main2   CALL Delay1
        CALL Look
        BTFSS 1F,0
        GOTO Main2      ;No whistle
        MOVLW 00        ;Whistle - turn off display
        MOVWF 06
Main3   CALL Delay1
        CALL Look
        BTFSC 1F,0
        GOTO Main3      ;whistle
        GOTO Main       ;no whistle

        END

This experiment detects the presence of light. A photo-darlington transistor is connected to the circuit via a plug and socket and exposed to light. The change in resistance of the photo-darlington transistor creates a voltage change across it and this is amplified by the circuit and delivered to an input of the microcontroller. The program turns on the 8 LEDs when the photo-darlington transistor detects change in illumination.
The photo-darlington transistor is connected to the circuit via a capacitor and only CHANGES in illumination are detected.
If the illumination is decreased, a point will be obtained where the circuit is sensitive to the changes in supply rail voltage. At this point the circuit will start to oscillate or MOTOR-BOAT.
The circuit must be re-designed to prevent this from occurring.
If the photo-darlington transistor is placed in a room with incandescent lighting, the 50 or 60Hz from the light will be detected. These pulses must be dealt with by the program to obtain a reliable HIGH/LOW pulse.

     ;Expt12.asm
     ;Project: Light Detection
List P = 16F84
#include <p16F84.inc>
__CONFIG 1Bh ;_CP_OFF & _PWRTE_ON & _WDT_OFF & _RC_OSC

        ORG 0           ;This is the start of memory for the program.
SetUp   BSF 03,5        ;Go to Bank 1
        CLRF 06         ;Make all port B output
        MOVLW 02        ;Load W with 0000 0010
        MOVWF 05        ;Make RA1 input
        BCF 03,5        ;Go to Bank 0 - the program memory area.
        CLRF 06         ;Clear display
        GOTO Main

Main    BTFSS 05,1      ;Test the input line on port A
        GOTO Main1      ;
        MOVLW 00h       ;
        MOVWF 06        ;Turn off LEDs
        GOTO Main
Main1   MOVLW 0FFh      ;
        MOVWF 06        ;Turn on LEDs
        GOTO Main

        END             ;Tells assembler end of program

GOING FURTHER

Once you complete the experiments in this project, you will want to write your own programs.
The website includes a PIC template called ”Blank_84.asm” This is a blank template with the set-up code and headings, in place.
The template can be found by clicking ”Blank_84.asm” for the file. Put it into a text program such as TEXTPAD, WORDPAD or EditPad. EditPad is on the site for downloading and is by far the best text program.
Copy ”Blank_84.asm” and give it another name so the original is available again.
Simply delete any code that is not needed and add your code to the sub-routines provided on the template.
It is best to use the pre-formatted template as it is important not to have any hidden formatting code to upset the assembler when it is being assembled.
If a program fails to assemble, re-type the faulty lines onto the template and re-assemble, as it may have picked up some hidden tabulating code or imaginary spaces. This is something that took us hours to locate. The assembler was looking for a label with an extra three spaces!
The “Burn” program for the Multi-Chip Programmer is included on the website as a .zip file and full instructions are given for setting up the Multi-Chip Programmer.

PIC LAB-1 FOR SCIENCE QUEST

The experiments in this article represent the starting-point in each group. It’s possible to expand any of the applications to incorporate monitoring or recording an event or combining two or more to create a completely new operation.
On the website we have added a page for Reader Experiments. You are invited to send in your ideas and programs and we will add them so you can share your ideas with with others. PIC LAB-1 is ideal as the foundation for a Science Quest project. The applications are almost limitless and the design of the PC board makes them very easy to implement. The secret is the microcontroller. It removes the need for lots of individual chips for counting, timing, displaying etc and reduces the complexity of a circuit.
If you intend entering a project for a quest, it is essential to prove the concept has been developed by yourself. The only way to do this is to keep your notes and prototypes and hand them in with the final design.
You can detect pulses from a switch, magnet, light-source, as well as audio frequencies, temperature (via a diode), degrees of rotation of a potentiometer, resistance, voltage, magnetism (hall effect device or coil) and others. The output can be on the 7-segment display or something you have added.
But the most impressive part of your project will be to do something new.
It may be to detect a scent, bacteria growth, onset of a fainting spell or epileptic fit, water purifying through a natural reed-bed, removing odours from a car in heavy traffic, guiding a wheelchair in a straight line, preventing super-market shopping carts being stolen, preventing cars colliding in the fog, guiding survivors through a smoke-filled building, making a sucking/blowing device for bed-ridden patients to operate equipment, TV’s etc. or one of a million applications needing processing power. There are thousands of simple requirements for invalid people, and this is where recognition will be highlighted.
You only need to design to the stage of preliminary findings. This will make your entry unique and you can take on further development at a later date.
It is the concept that will win you an award and PIC LAB-1 can help with many of these ideas.

WRITING A PROGRAM

To write a program for the PIC16F84 microcontroller, or modify any of the programs we have written, you will need the instruction-set. This consists of about 35 “English-like” instructions, that are able to be read by you as well as a program that will convert them into machine-code numbers for the microcontroller.
These “English-like” instructions are called mnemonics and the Instruction-Set for the PIC16F84 is available by clicking: F84INSTRUCTION-SET.
Definitions for each instruction plus articles on PIC Programming are available in the ”PIC Programming Course.” This is on the POPTRONICS Interactive Edition website. Easy subscribing details are provided on a link.
Go to the menu of your computer and create a new folder called Experiments. Place it inside your PIC LAB-1 folder.
You will need blank template on which you will be able to write your own programs.
Download the blank template BlankF84.asm file into Experiments folder.
Open a text editor program such as TEXTPAD or NOTEPAD and open the file BlankF84.asm Rename it to Expt-1.asm or the name of your new project.
Edit the code on the template and add your own code to perform a simple operation that takes an input signal from a switch and outputs the result to a LED (copy some of the code from an experiment and add a few lines of your own).
Save the file. Make sure it is saved as .asm as the text editor will naturally save it as a .txt file.
Go to the Site Map above and click on MPASM
Move MPASM.exe to your desktop folder.
It will appear on your front screen.
Click on the Icon on your desktop and MPASM v02.70 will appear. Make sure the Radix is Hexadecimal, Warning Level: All Messages, Hex Output: INHX8M, Generated Files: List File, Case Sensitive: NOT Ticked, Macro Expansion: Default, Processor: 16F84, Tab Size: 8, Save Settings on Exit: TICKED.
Press Browse to locate Expt-1.asm file. The file name will appear in the top address box. Press Assemble it to get a small dialog box with NO error and no warnings. This will produce a .cod .hex and .lst in the same directory as .asm
If you get an error, the .hex file will not be generated, so go to your Text Editor and load the .lst file.
Read the .lst file and it will explain where the fault is located.
Go to the .asm file and make the correction(s).
Re-assemble the file again.
Here’s a tip: To make sure you are actually assembling the corrected version, I suggest you save the file as: Expt-1a.asm
When the file assembles correctly and a green background appears on the dialog box after assembly, you will have a .hex file in the same directory.
You now need a program to take the .hex file and burn it into the chip using the Multi Chip Programmer.
The software program is: ICPROG.
See IC-Prog.exe and a help file: ICPROG-Help (IC-Prog.chm).
Place ICPROG.exe into your desktop folder and it will appear on your screen.
Go you your front-screen (desktop) and open a text editor program such as TEXTPAD or NOTEPAD. Open the file to be burnt, such as: Expt-1.hex Open ICPROG.
On the small window showing the types of chips the programmer is able to program, select PIC 16F84.
In the oscillator window, select RC.
In the fuses windows, remove all the ticks.
Click on the “open file” icon on the left hand side of the screen. Find Expt1.hex and load it into the programmer. A tick will appear in the WDT window to indicate a file has been loaded. Remove the tick.
Make sure Multi Chip Programmer has been fitted to “Com1” via a serial cable and the red LED on the Multi Chip Programmer is active.
Click on the IC Icon with the “lightening” and a dialog box with “Do you really want the program the device?” will appear.
Click “yes” and the orange and green LEDs will illuminate on the Multi Chip Programmer and the screen will indicate the chip has been programmed correctly.
Remove the chip and fit it to the PIC LAB-1 project. Fit any necessary input devices and switch the project ON. The LEDs on the output will respond.
If every thing has gone successfully, you will have “burnt” your first program.
Only some of the steps above will have to be repeated, but this is how the program comes along.
Add only a few lines at a time so that fault-finding will be limited to a small part of the program.
Once you get the basics working you can add add sub-routines for counting, displaying, etc and gradually build up the project to impressive dimensions.You will find many of your requirements can be met with the components on the PIC LAB-1 and by simply adding a sub-board, a more-advanced project can be created.
When you get the design working, you can CAD the artwork for the board. Don’t forget to include a top layer or legend. This is absolutely essential if you want to produce a quality item - but is not essential for a Science Project.
All the programs needed to create a Printed Circuit Board are available on the web.

CREATING A PROJECT

To create a project you need to follow a few simple steps.
But before you start, there is one factor you must remember. Everything you do must consist of small increments and it is essential to start at the beginning with something very simple. This is the only way to create a program.
As each stage of a program works correctly, it can be saved with its own reference number so that you can go back to it if a problem develops further down the track.
But writing a program is not the first step.
A circuit needs to be developed. You should look through books and magazines to see how it has been done using discrete technology. Collect as much information as possible to help you with your design and see the complexity of the circuit.
Projects requiring 3 or more chips will be in the “economics zone” as well as those requiring more features than already available.
The aim will be to use as many of the “building blocks” on the PIC LAB-1 as possible. They can be modified and extended to suit your application.
The circuit is initially laid out as BLOCKS showing the input, the micro and output sections. Pin numbers and component values do not have to be worked out until later.
Start with a simple part of the circuit such as turning on a LED when a switch, is pressed.
Write a program to make sure the micro is detecting the input device and outputting the result on the LED.
Pick out any of the experiments we have designed for the PIC LAB-1 and see how we have written the instructions. Add instructions of your own.
Make sure this part is working before adding another section.
Gradually build up the operation of the project by adding a small section at a time. It’s a slow process but it’s sure.
Quite often you can borrow previous routines to speed up the process and eventually the project is complete.

CONCLUSION

This is not the end. It’s just the beginning. Your rewards are just about to start.
There are so many things you can do.
We have covered many ideas in this project and it’s just a matter of looking into something that “sparks an interest” and running with it.
Everything you need is on the site and we have produced more pages to show how to go further with more advanced programming.

The next Pages …

The next pages explain the theory behind some of the input/output devices and how to connect them to a microcontroller.
We also have many more experiments involving more-complex programming with two or more elements.
Also included is a complete LIBRARY OF ROUTINES for the PIC LAB-1, arranged in alphabetical order.
Each time you need a step in the development of a program, go to the library for suggested instructions. This will help you build a program very quickly and up to 80% to 90% of most programs can be created this way.

The next page has a strategy project called “21”. It is the old 21 matches game where you take 1, 2, or 3 matches, leaving your opponent with the last match. It shows programming to a tee. Especially the “strategy” section, where all the “thinking” takes place.
This is possibly the most complex type of project to be covered, using a PIC16F84 chip but the straight-forward layout will help you work through each of the sections.