Home


 
Kits are available for this project from
Talking Electronics for $20.00 plus $7.00 postage.

See more projects using micros:
Elektor,EPE,Silicon Chip
 

 

This is a great game to test your skills.

This project has been adapted from an experiment by John Ridley Stroop, who published his work in 1935. Basically it is a "trick." It is a trick in that you are required to answer a question at a "second level of thinking."
In our test we have three tri-coloured LEDs and below each is a push-button.
When a LED illuminates, your immediate response is to push the button below the LED.
But this is not the requirement.
The LED will illuminate as one of three colours. Red, Orange or Green.
You are required to push the first button for red, the middle button for orange and the third button for green.
In other words you have to divorce yourself from the urge to push the closest push-button and work on the colour-requirement.
Obviously you will become more-adept at this over a period of time but the most important results will come from the first few attempts.
That's why it will be interesting to have your friends take a test.
The "Stroop effect" has been used to investigate the psychological capacities of a person. In fact it introduces capabilities that have never been investigated before. Although I don't believe in anything to do with psychology, this test is considered to measure selective attention, cognitive flexibility and processing speed. About the only word I understand is "processing speed" and that's how our game works. It runs for 20 seconds and gives a score on the 7-segment display.
You are required to get as many matches as possible in 20 seconds.
The game comes on by displaying the letters "S-t-r-o-o-P" on the 7-segment display and then sits ready for your first try.
The single digit display can actually display up to 99 as it flashes the tens digit first and then the units. It repeats this three times and turns off, ready for the second game. Push any button to start.

The CIRCUIT
The circuit consists of three push-buttons, three tri-coloured LEDs and a 7-segment display made from individual LEDs. All the "timing," outputting and switch-detection is done in the PIC16F628 microcontroller.
The board contains 5 pins for In-Circuit Programming so the program can be changed and modified at any time.
The resistor values for the LEDs have been chosen to get the maximum brightness, using the 25mA available from each output.
The 7-segment display is made up of 14 individual LEDs, with two LEDs in series for each segment. This gives a voltage drop of approx 3.4v and a 22R current-limit resistor is needed.
RB7 is used for the switch inputs and this is also used as the data line when programming. To allow the data to enter the chip while programming, a 2k2 resistor has been added as the 100n upsets the data line if it is connected directly to the programming pin.
The resistor values for the switches have been chosen to separate the timing for each switch and make it easy to recognise in the program. 


STROOP GAME CIRCUIT
The 7-segment display actually has 2 yellow LEDs in series for each segment.
The unusual output from the chip suits the layout of the board.

CONSTRUCTION
You can build the circuit on any type of Proto board or design your own PC board.
Use 4 - AAA cells and not button cells as button cells do not have low enough impedance to keep the voltage high when all the LEDs are illuminated and the chip hic-cups and flashes the display.

 


The complete STROOP GAME
The surface-mount components are mounted under the board



The surface-mount components are clearly identified


The PROGRAM
The program has been kept simple to make it easy to understand. Very few Boolean expressions have been used as they take a lot of understanding and "working out" as to the the outcome of the instruction.
We note that a simpler program was written in "C" and it failed to compile into the 1024 memory locations, so I don't know how the inefficiency of higher-level programming would relate to this project.
In any case, we have used the 35 instructions that come with the chip and this makes fault-finding very easy as you know the fault lies in the code you have generated.
As long as you only introduce a small amount of code at a time, you will be able to gradually get a program up-and-running.     

The interesting feature of the program is the overall timing. The micro is counting in the background via timer1 and this consists of two files (registers) capable of counting to 65,536. A prescaler has been added to increase the count to 524,288. This is about half a second.
When the timer overflows, the program-execution is interrupted and the micro goes to location 4 (called the Interrupt location  where it finds an instruction to go to a sub-routine called: "isr."  At isr, another file is decremented (_20Secs) thirty-nine times and this produces the 20 seconds duration for each game.
(Point to remember: Timer0 does not produce a long delay, so Timer1 has to be used).

The buttons are detected by charging the 100n and waiting 20mS to see if the capacitor has discharged. We know the cap will discharge in less than 8mS if a button is pushed.
The program now knows if a button is pushed or not.
It makes a second pass, if a button is pushed, to work out which button has been pressed.
The first button will discharge the cap in less than 2mS, the second button will discharge the cap in less than 4mS and the third button will discharge the cap in less than 8mS.
The program now performs a 1mS loop, looking for a LOW on the detecting pin.
It will exit with a value of 1-8.
The program now decrements the count file and and if it is zero after one or two decrements, button 1 has been pressed. It continues with decrements until it finds the button.

RANDOM NUMBER
The most difficult thing to produce on a computer is a random number.
You can combine and XOR various files or use a table. but nothing generates a truly random result.
We have used the "waiting time" when a player waits to provide an answer and this generates a new random number, while the program is actually using a previously generated number for the play in progress. That's why the random number has to be generated in a sub-routine called "Create," and this number is passed to the Random Number file for use in the next try.

The program contains a number of very important subroutines that you will be able to "cut and paste" for projects in the future.

MORE
For more details on modifying the program and burning the PIC chip, see Talking Electronics website and click on Elektor,EPE,Silicon Chip in the index.
You can find details of: 
PICkit-2 and Adapter connected for In-Circuit Programming at this link.


Here is the file you will need for "burning" your chip and/or modifying the program. It comes as .asm, .txt and .hex for using as a file to modify, or to read, or to burn a new chip:

Stroop.asm
Stroop.txt
Stroop.hex

The kit comes with a pre-programmed PIC chip, see parts list below.
	
;****************************************************************
;Started 18/6/2009	
;STROOP - Press a button according to the colour of the LED
;
;Port A drives 3 tri-coloured LEDs
;Port B drives 7 segment display and keys
;****************************************************************

	list P = 16F628	;microcontroller 
	include 	;registers for F628


	__Config 	_cp_off & _lvp_off & _pwrte_on 
		& _wdt_off & _intRC_osc_noclkout & _mclre_off
	
;code protection - off
;low-voltage programming - off
;power-up timer -  on
;watchdog timer - off
;use internal RC for 4MHz - all pins for in-out


;****************************************************************
; variables - names and files
;****************************************************************


		;Files for F628 start at 20h 
 
						 			
temp1		equ 20h	;for delay
temp2		equ 21h	;for delay
count		equ 22h	;counts loops for switch
Random		equ 23h	;random number file
units		equ 24h	;
tens		equ 25h	;
Sw_Flag		equ 26h	;
_20Secs		equ 27h	;file for counting up to 20 seconds
loops		equ 28h	;loops for number display
Produce		equ 29h	;produce random number
temp3		equ 2Ah	;for 500mS delay

;****************************************************************
;Equates
;****************************************************************
status		equ	0x03
cmcon		equ	0x1F
rp1		equ	0x06
rp0		equ	0x05
portA 		equ 	0x05
portB 		equ 	0x06

z		equ	0x02


;****************************************************************
;Beginning of program
;****************************************************************


Start	org	0x00	;program starts at location 000
	goto	Stroop	;goto Stroop
	nop		
	nop		;NOPs to get past reset vector address
	org	4
	goto	isr	


SetUp	bsf	status,rp0	
	movlw	b'00000000'	;Make RA output
	movwf	05h		;trisA
	clrf	06h		;trisB   Make all RB output
	movlw	b'10000000'; 
	movwf	OPTION_REG	; x000 0000 x=1=weak pull-ups disabled
	bcf	status,rp0	;select programming area - bank0 	
	movlw	b'00000000'	;6,7=0 disables all interrupts  
	movwf 	INTCON		;until we want timing to commence
	clrf	Sw_Flag
	movlw	07h		;turn comparators off 
	movwf	cmcon		
	clrf	portA
	clrf	portB	
	clrf	units		
	clrf	tens			
	clrf	Random		;random will be 1-9 
	clrf    Produce
	movlw	.39
	movwf	_20Secs
	goto 	Main					

;*************************************
;* Tables 			*
;*************************************

table1	addwf   PCL,F    	;02h,1  
	nop			;display random LED colour
        retlw   b'00000001'     ; Led A - red
        retlw   b'00000011'     ; Led A - orange
        retlw   b'00000010'     ; Led A - green
        retlw   b'00000100'     ; Led B - red
        retlw   b'00001100'     ; Led B - orange
        retlw   b'00001000'     ; Led B - green
        retlw   b'01000000'     ; Led C - red
        retlw   b'11000000'     ; Led C - orange
        retlw   b'10000000'     ; Led C - green
        
table2 addwf PCL,F ;02h,1 add W to program counter 
	retlw 	b'01111110' ; "0" -|F|A|B|E|C|D|G
	retlw 	b'00010100' ; "1" 
	retlw 	b'00111011' ; "2" 
	retlw 	b'00110111' ; "3" 
	retlw 	b'01010101' ; "4" 
	retlw 	b'01100111' ; "5" 
	retlw 	b'01101111' ; "6" 
	retlw 	b'00110100' ; "7" 
	retlw 	b'01111111' ; "8" 
	retlw 	b'01110111' ; "9" 


;Table 3 creates 1 on the left of the display for "10's"

table3 	addwf PCL,F ;02h,1 add W to program counter 
	retlw 	b'01111110' ; "0" -|F|A|B|E|C|D|G
	retlw 	b'01001000' ; "1" 
	


;************************************
;* Sub routines			*
;************************************

Attract		;flash all red, orange  green then random LED	
		
	movlw	b'01000101'     ; all red		
	movwf	portA
	call	_250mS
        movlw	b'11001111'     ; all orange
	movwf	portA
	call	_250mS             
        movlw	b'10001010'     ; all green
        movwf	portA
	call	_250mS 
	clrf	portA
	call	_250mS 
	call	_250mS              
	retlw	00
					
	;create random number from 1 to 9 for table 1

Create 	incf Produce,f 
	movlw .10 ;put ten into w
	xorwf Produce,0 ;compare Produce file with ten
	btfss status,2 ;zero flag in status file. 
	goto $+3      ;Will be set if Produce is ten
	clrf Produce
	incf Produce,f
        retlw 00 
					

	;Delays
	
_1mS	nop
	decfsz 	temp1,f
	goto 	_1mS
	retlw 	00
			

_10mS	movlw	0Ah
	movwf	temp2
_b	nop
	decfsz 	temp1,f
	goto 	_b
	decfsz 	temp2,f
	goto 	_b	
	retlw 	00		
		
_100mS	movlw	.100
	movwf	temp2
_c	nop
	decfsz 	temp1,f
	goto 	_c
	decfsz 	temp2,f
	goto 	_c	
	retlw 	00
				
_250mS	movlw	.240
	movwf	temp2
_d	nop
	decfsz 	temp1,f
	goto 	_d
	decfsz 	temp2,f
	goto 	_d	
	retlw 	00	
		
_500mS	movlw	02
	movwf	temp3
	call	_250mS		
	decfsz	temp3,f		
	goto	$-2
	retlw	00
		
_3Sec	movlw	.12
	movwf	temp3
	call	_250mS		
	decfsz	temp3,f		
	goto	$-2
	retlw	00	
		
	
;interrupt service routine		

isr	nop		
	bsf	status,rp0 	;Bank 1				
	bsf	PIE1,0		;,0 1=enables TMR1 interrupt
	bcf	status,rp0	;bank 0 		
	bcf	PIR1,0		;clear TMR1 overflow flag
	bsf	INTCON,7	;This instruction is needed HERE!!!	
	bsf	INTCON,6	;1=enable all peripheral interrupts	
	decfsz	_20Secs,f	;creates 20Sec delay for each game.
	retfie
		
	bcf	PIE1,0		;,0 0=disables TMR1 interrupt
	bcf	INTCON,6	;0=disable all peripheral interrupts
		
	decf	tens,f
	incf	tens,f
	movlw	.10
	subwf	units,f
	btfsc	status,0	;test carry bit for borrow
	goto	$-4
	movlw	.10
	addwf	units,f
		
	movlw	03
	movwf	loops
				
	movf	tens,w
	btfsc	status,z
	goto	$+.18		;If 0-9, display single digit
	call	table3
	movwf	portB
	call	_500mS
	call	_250mS
	clrf	portB
	call	_250mS		
	movf	units,w
	call	table2
	movwf	portB
	call	_500mS
	call	_250mS
	clrf	portB
	call	_500mS
	call	_500mS
	decfsz	loops,f
	goto	$-.18
	goto	SetUp
								
	movf	units,w
	call	table2
	movwf	portB
	call	_3Sec		
	goto	SetUp
		
		
	; show Stroop
		
Stroop	bsf	status,rp0	
	clrf	06h		;trisB   Make all RB output
	movlw	b'10000000'; 
	movwf	OPTION_REG	; x000 0000 x=1= weak pull-ups disabled	
	bcf	status,rp0	;select programming area - bank0 	
	movlw	07h		;turn comparators off 
	movwf	cmcon		
	clrf	portA		

	movlw	b'01101101'     ; "S"	
	movwf	portB
	call	_500mS
	clrf	portB
	call	_250mS
	movlw	b'01111000'     ; "t"
	movwf	portB	
	call	_500mS
	clrf	portB
	call	_250mS
	movlw	b'01010000'     ; "r"
	movwf	portB	
	call	_500mS
	clrf	portB
	call	_250mS
	movlw	b'01011100'     ; "o"
	movwf	portB	
	call	_500mS
	clrf	portB
	call	_250mS
	movlw	b'01011100'     ; "o"
	movwf	portB	
	call	_500mS
	clrf	portB
	call	_250mS
	movlw	b'01110011'     ; "P"	
	movwf	portB
	call	_500mS
	clrf	portB
	goto 	SetUp
		
				
Sw	clrf	Sw_Flag
	bsf	status,rp0			
	bcf	06h,7		;trisB   Make bit 7 output
	bcf	status,rp0
	bsf	portB,7		;make bit 7 HIGH	
	call	_1mS		;create delay to charge 100n		
	bsf	status,rp0			
	bsf	06h,7		;trisB   Make bit 7 input
	bcf	status,rp0		
	call	_10mS
	call	_10mS
	btfsc	06h,7		;if HIGH, button not pushed	
	retlw	00				
	clrf	count
	bsf	status,rp0			
	bcf	06h,7		;trisB   Make bit 7 output
	bcf	status,rp0
	bsf	portB,7		;make bit 7 HIGH	
	call	_1mS		;create delay to charge 100n		
	bsf	status,rp0			
	bsf	06h,7		;trisB   Make bit 7 input
	bcf	status,rp0					
SwA	call	_1mS
	call	_1mS
	incf	count,f
	btfsc	06h,7		;is input HIGH?				
	goto	SwA		;count exits with 1-8
	bsf	Sw_Flag,0	;button has been pushed
	decfsz	count,f
	goto	$+3
	bsf	Sw_Flag,1
	retlw	00
	decfsz	count,f
	goto	$+3
	bsf	Sw_Flag,1
	retlw	00
	decfsz	count,f
	goto	$+3
	bsf	Sw_Flag,2
	retlw	00
	decfsz	count,f
	goto	$+3
	bsf	Sw_Flag,2
	retlw	00
	decfsz	count,f
	goto	$+3
	bsf	Sw_Flag,2
	retlw	00		
	bsf	Sw_Flag,3
	retlw	00
		
		
		;switch released		
		
Sw_Rel	clrf	Sw_Flag
	bsf	status,rp0		
	bcf	06h,7		;trisB   Make bit 7 output
	bcf	status,rp0
	bsf	portB,7		;make bit 7 HIGH	
	call	_1mS		;create delay to charge 100n		
	bsf	status,rp0			
	bsf	06h,7		;trisB   Make bit 7 input
	bcf	status,rp0		
	call	_10mS
	call	_10mS
	btfsc	06h,7		;if HIGH, button not pushed	
	retlw	00				
	bsf	Sw_Flag,0
	retlw	00
		
				
;*************************************
;* Main 				*
;*************************************

	;Stroop comes on "blank" looking for button-push
Main	call	Create
	call	Sw
	btfss	Sw_Flag,0	
	goto	$-3	;no
	;button pressed and Random Number generated
							
	;Stroop goes into ATTRACT mode then stops on Random LED

	call	Attract					
							
	;Display Random LED colour, waiting for sw press
			

;****************************************************************
;* Start Timer1 to count 20 seconds in the background		*
;****************************************************************
		
	bsf	status,rp0 	;Bank 1			
	movlw	b'10000000'	; 
	movwf	OPTION_REG	;x000 0000 x=1= weak pull-ups disabled 
	bcf	status,rp0	;bank 0 		
				
	movlw	b'11000000'	;b'11000000'
	movwf 	INTCON		;,0  1=RB port change interrupt flag
				;,1  1=RB0 interrupt occurred
	;bcf	INTCON,2	;1=TMR0 overflowed. Clear overflow flag 
	;bcf	INTCON,3	;1=enable RB port change interrupt
	;bcf	INTCON,4	;1=enable RB external interrupt		
	;bsf	INTCON,5	;1=enable TMR0 overflow (interrupt)
	;bcf	INTCON,6	;1=enable all peripheral interrupts
	;bsf	INTCON,7	;1=enable all unmasked interrupts
				
	movlw	b'00110101'	;b'00110001'			
	movwf	T1CON		;,7  not used
				;,6 0=Timer1 is ON
				;,5,4  11=8 prescale (max) 01=1:2
				;,3 bit ignored
				;,2 This MUST BE SET!!!!!!
				;,1 0=int clock 
				;,0 1=enable timer1 
							
	bsf	status,rp0 	;Bank 1	(Must use Bank1)	
	bsf	PIE1,0		;,0 1=enables TMR1 interrupt	
	bcf	status,rp0	;bank 0 
	bcf	PIR1,0		;clear TMR1 overflow flag
		
	clrf	TMR1L		;clear the Timer1 low register
	clrf	TMR1H		;clear the Timer1 high register
				;Timer0 is not used 		
				; will go to isr when overflow in TMR1
				;0.52 sec when prescaler=1:8  524,288uS	
		
	bsf	status,rp0 	;Bank 1	(Must use Bank1)	
	bsf	PIE1,0		;,0 1=enables TMR1 interrupt	
	bcf	status,rp0	;bank 0 
		
			;game has started with random LED	
							
Main2	movf	Produce,w					
	movwf	Random		
	call	table1
	movwf	portA		;show random number
				;program gets to here after 1 press	
		
	call	Create
	call	Sw
	btfss	Sw_Flag,0	;has button been pressed?
	goto	$-3		;no
				;button pressed				
							
	movlw	01
	xorwf	Random,0	;yes
	btfss	status,z	;test zero bit for compare
	goto	$+5
	btfss	Sw_Flag,1	;random=1	Is sw = button1
	goto	release
	incf	units,f
	goto	release	
			
	movlw	02
	xorwf	Random,0	;yes
	btfss	status,z	;test zero bit for compare
	goto	$+5
	btfss	Sw_Flag,2	;random=2	Is sw = button2
	goto	release
	incf	units,f
	goto	release	
		
	movlw	03
	xorwf	Random,0	;yes
	btfss	status,z	;test zero bit for compare
	goto	$+5
	btfss	Sw_Flag,3	;random=3	Is sw = button3
	goto	release
	incf	units,f
	goto	release		
		
	movlw	04
	xorwf	Random,0	;yes
	btfss	status,z	;test zero bit for compare
	goto	$+5
	btfss	Sw_Flag,1	;random=4	Is sw = button1
	goto	release
	incf	units,f
	goto	release			
		
	movlw	05
	xorwf	Random,0	;yes
	btfss	status,z	;test zero bit for compare
	goto	$+5
	btfss	Sw_Flag,2	;random=5	Is sw = button2
	goto	release
	incf	units,f
	goto	release		
				
	movlw	06
	xorwf	Random,0	;yes
	btfss	status,z	;test zero bit for compare
	goto	$+5
	btfss	Sw_Flag,3	;random=6	Is sw = button3
	goto	release
	incf	units,f
	goto	release			
		
	movlw	07
	xorwf	Random,0	;yes
	btfss	status,z	;test zero bit for compare
	goto	$+5
	btfss	Sw_Flag,1	;random=7	Is sw = button1
	goto	release
	incf	units,f
	goto	release			
		
	movlw 	08
	xorwf 	Random,0 	;yes
	btfss 	status,z 	;test zero bit for compare
	goto 	$+5
	btfss 	Sw_Flag,2 	;random=8 Is sw = button2
	goto 	release
	incf 	units,f
	goto 	release

	;random has to be 9

	btfss 	Sw_Flag,3 	;random=9 Is sw = button3
	goto 	release
	incf 	units,f		
					
release	clrf	portA
	call	_500mS			
	goto	Main2

	End	

THE GAME
The game is played by switching the project on and seeing which colour is illuminated.
Press the first button if the colour is RED, the second button if the colour is Orange and the third button if the the colour is GREEN.
The aim is to get as many correct in 20 seconds.
The score appears on the 7-segment display. The display flashes the tens digit and then the units. It then blanks for 2 seconds and repeats the number. It does this 3 times then turns off.

 

Stroop
Parts List

Cost: au
$
20.00 plus $7 postage
Kits are available

7  -  22R  (220) SM resistor
6  -  150R  (151) SM resistor
1  -  2k2 (222) SM resistor
1  -  22k (223)  SM resistor
1  -  47k  (473) SM resistor
1  -  100k (104)  SM resistor

2  -  100n SM capacitors

14  - Orange SM LEDs
1  -  1N4148 diode
3  -  tri-coloured LEDs
1  -  SPDT mini slide switch
3  -  mini tactile push buttons

20cm  - very fine solder 
1  -  18 pin IC socket 

1  -  PIC16F628 chip (with Stroop routine)
4  -  AAA cells (do not use button cells
               - they produce false operation)
1  -  4-cell battery holder
1  -  Stroop PC board
 
JUST THE MICRO:
Pre-programmed PIC16F628 micro with Stroop routine $10.00 plus $5.00 post

GOING FURTHER
Th
is project is one of a number of projects using a PIC microcontroller.
The overall concept of Talking Electronics is to show what can be done with a "micro" and it uses surface mount componentry.
Once you go to SM, you will never go back to through-hole components. 
Surface mount may be fiddly and slower to solder but the end result is a much smaller project and it looks much simpler.
With the Stroop project, the challenge is to add more features.
You can change the program to decrement the score for a false button-press or cancel the score completely.
You can also increase the time to get a better spread of results.
No matter what you do, the fact that you have modified the program is the important part.
Only by modifying the program will you learn anything.

This project is one of 10 ideas we have designed for greeting cards. Instead of opening a $6.00 card to see the words "Happy Birthday," you will also get a game using micro-thin electronics.
The only thing that let us down was the cost of the micro. The PIC chip costs 33 cents in a large quantity but the Chinese version MV08 costs 5 cents as a "die"  This is a COB (Chip On Board) version but the minimum quantity is 100,000. It's an 8-pin chip but the circuit will have to be re-designed to use it.

 8/8/14