Combinaton Gate access

**Darrel Taylor** · - 13th February 2007, 06:37

Originally Posted by Joe S.

Is that because it has not gone back to the scan routine? Should I have used goto and resume or just put return after each if...then statement?

None of the above.
It's because it's the Wrong Logic for the job.

With an IF ELSE ENDIF, there are only 2 possibilities. True or False.
And that result is based entirely on 1 expression ... (ByteA = 7) and (combocount=0)

So essentially, you're asking it if the Whole combination is correct, by looking at just one keypress.

Then by stacking up 5 IF ELSE ENDIF's together, since they can't ALL be true at the same time, there will always be 4 of them saying the combination is Wrong.

Much like in real life, decisions aren't always as easy as True or False.
Usually, you'll have to consider several different things Before making a decision.
And those "things" may happen at different times, so you may not be able to make a decision until more information is available.

So instead of just the True or False, Black or White. Here's the answer.
You also need to be able to say "I don't know yet".

This is where just IF THEN is more useful.
Instead of only the 2 possibilities, IF THEN has Infinite possibilities.
Granted, It's either TRUE, or it's NOT, but by not taking action when it's not true, it's the same as saying "I don't know".

So now you can stack those up if you want, because they won't be interfering with each other by making their own decisions independently.
They only act on what they KNOW to be TRUE.

Here's what I mean...Still not the way I would do it, but for the sake of argument...

Code:

combo:
    IF (combocount = 0) and (ByteA = 7)   then GoodKey
    IF (combocount = 1) and (ByteA = 8)   then GoodKey
    IF (combocount = 2) and (ByteA = "A") then GoodKey
    IF (combocount = 3) and (ByteA = 5)   then GoodKey
    IF (combocount = 4) and (ByteA = "D") then GoodKey
    combocount = 0 ; invalid keypress
return

GoodKey:
    combocount = combocount + 1
    if combocount = 5 then GrantAccess
return

**Archangel** · - 13th February 2007, 07:46

Originally Posted by Darrel Taylor

None of the above.
It's because it's the Wrong Logic for the job.

With an IF ELSE ENDIF, there are only 2 possibilities. True or False.
And that result is based entirely on 1 expression ... (ByteA = 7) and (combocount=0)

So essentially, you're asking it if the Whole combination is correct, by looking at just one keypress.

Then by stacking up 5 IF ELSE ENDIF's together, since they can't ALL be true at the same time, there will always be 4 of them saying the combination is Wrong.

Much like in real life, decisions aren't always as easy as True or False.
Usually, you'll have to consider several different things Before making a decision.
And those "things" may happen at different times, so you may not be able to make a decision until more information is available.

So instead of just the True or False, Black or White. Here's the answer.
You also need to be able to say "I don't know yet".

This is where just IF THEN is more useful.
Instead of only the 2 possibilities, IF THEN has Infinite possibilities.
Granted, It's either TRUE, or it's NOT, but by not taking action when it's not true, it's the same as saying "I don't know".

So now you can stack those up if you want, because they won't be interfering with each other by making their own decisions independently.
They only act on what they KNOW to be TRUE.

Here's what I mean...Still not the way I would do it, but for the sake of argument...

Code:

combo:
    IF (combocount = 0) and (ByteA = 7)   then GoodKey
    IF (combocount = 1) and (ByteA = 8)   then GoodKey
    IF (combocount = 2) and (ByteA = "A") then GoodKey
    IF (combocount = 3) and (ByteA = 5)   then GoodKey
    IF (combocount = 4) and (ByteA = "D") then GoodKey
    combocount = 0 ; invalid keypress
return

GoodKey:
    combocount = combocount + 1
    if combocount = 5 then GrantAccess
return

I Get it, Thanks Darrel, then If you were inclined to code that way, would this be a place for select case? It seems as though the THEN Goodkey scenerio would make the combination work if out of sequence? Or would the loop cancel before combocount reaches 5 ? Oh your code works SWEET! Thanks Again.
Joe

**Darrel Taylor** · - 13th February 2007, 08:32

would this be a place for select case?

You could, but it just uses more code space. It's pretty much a Select Case the way the last example is shown. But here's a Select Case version...

Code:

combo:
    Select CASE combocount
        Case 0 : if ByteA = 7   then GoodKey
        Case 1 : if ByteA = 8   then GoodKey
        Case 2 : if ByteA = "A" then GoodKey
        Case 3 : if ByteA = 5   then GoodKey
        Case 4 : if ByteA = "D" then GoodKey
    END SELECT
    combocount = 0
return
    
GoodKey:
    combocount = combocount + 1
    if combocount = 5 then GrantAccess
return

Or, just to keep things nice and confusing, you could also do this...

Code:

Combo:
    Lookup  combocount,[7,8,"A",5,"D"], NextDigit
    if ByteA = NextDigit then 
        combocount = combocount + 1
        if combocount = 5 then GrantAccess
    else
        combocount = 0
    endif
return

It seems as though the THEN Goodkey scenerio would make the combination work if out of sequence?

Nope, that can't happen. You should run the program in MCSP debugger and watch what happens. After watching debuggers for awhile, you'll be able to see it in your mind, and programming will go a lot smoother. And eventually, you won't even need the debugger anymore, or the PIC. It'll run inside your head.

Oh your code works SWEET! Thanks Again.

No Problemo!

**Leonardo** · - 13th February 2007, 15:00

Hello to all,

I have followed east subject and it seems to me excellent, my english is not very good but treatment for understanding what you say.

This it is a interesting project, I am working to record the data in eeprom, when it has ready the code send.

**Leonardo** · - 13th February 2007, 16:12

It works of this form?

Code:

@MyConfig = _HS_OSC & _WDT_OFF & _PWRTE_ON & _LVP_OFF 
@MyConfig = MyConfig & _BODEN_OFF 
@ __config  MyConfig
'@ __CONFIG _HS_OSC & _WDT_ON & _PWRTE_ON  & _LVP_OFF & _CP_OFF
Define PIC16F877A
@ errorlevel -230
CMCON  = 7  
ADCON1 = 7 
define OSC 20
TrisD = %00000000

DEFINE LCD_DREG PORTA
    DEFINE LCD_DBIT 0
    DEFINE LCD_RSREG PORTA
    DEFINE LCD_RSBIT 5
    DEFINE LCD_EREG PORTA
    DEFINE LCD_EBIT 4
    DEFINE LCD_BITS 4
    DEFINE LCD_LINES 4

    include "keypad.bas"
pause 1000
lcdout 254,1
lcdout 254,128,"PIC Self Test"
pause 1000
    
    DEFINE KEYPAD_ROW        4        ' 4 ROW keypad       
    DEFINE KEYPAD_ROW_PORT   PORTB    ' ROW port = PORTB
    DEFINE KEYPAD_ROW_BIT    4        ' ROW0 = PORTB.4
    DEFINE KEYPAD_COL        4        ' 3 COL keypad
    DEFINE KEYPAD_COL_PORT   PORTB    ' COL port = PORTB
    DEFINE KEYPAD_COL_BIT    0        ' COL0 = PORTB.1
    DEFINE KEYPAD_DEBOUNCEMS 50       ' debounce delay = 50 mSec
    DEFINE SCAN_ONCE         1

    OPTION_REG.7 = 0        ' Enable internal crap pull-up :D

    PORTB = 0             '  
    TRISB = %11110000     '
    Flags = 0  
    ByteA var byte         '
    Combocount var byte 
        INTCON = %10001000    ' Enable global interrupt
                          ' Enable interrupt on PORTB change
    on interrupt goto KeypadInt
    CLEAR

Portd.2 = 0
combocount = 0

Init:    
    lcdout $FE,1,"Press any Key"
 disable
KeypadINT:    
@ READKEYPAD _ByteA
    TRISB=%11110000
    PORTB=0
    INTCON.0=0
    resume
enable   
    
    
Start:
    if ByteA then
    If ByteA = 4  then ByteA = "A"
    if ByteA = 5  then ByteA = 4
    if ByteA = 6  then ByteA = 5
    if ByteA = 7  then ByteA = 6
    if ByteA = 8  then ByteA = "B"
    if ByteA = 9  then ByteA = 7
    if ByteA = 10 then ByteA = 8
    if ByteA = 11 then ByteA = 9
    if ByteA = 12 then ByteA = "C"
    if ByteA = 13 then ByteA = "*"
    if ByteA = 14 then ByteA = 0
    if ByteA = 15 then ByteA = "#"
    if ByteA = 16 then ByteA = "D"
    if ByteA != 0 then  gosub combo
        
        ByteA = 0
        pause 1000
        goto init
        'else
           
else   
endif
goto start

combo:
    IF (combocount = 0) and (ByteA = 7)   then GoodKey
    IF (combocount = 1) and (ByteA = 8)   then GoodKey
    IF (combocount = 2) and (ByteA = "A") then GoodKey
    IF (combocount = 3) and (ByteA = 5)   then GoodKey
    IF (combocount = 4) and (ByteA = "D") then GoodKey
    combocount = 0 ; invalid keypress
return

GoodKey:
    combocount = combocount + 1
    if combocount = 5 then GrantAccess
return
goto init ' Combination 78A5D


GrantAccess:
hight portd.2
pause 1000
low portd.2
pause 1000

ByteA = 0
Combo1 = 0


end

**Archangel** · - 13th February 2007, 22:36

Originally Posted by Leonardo

It works of this form?

Code:

@MyConfig = _HS_OSC & _WDT_OFF & _PWRTE_ON & _LVP_OFF 
@MyConfig = MyConfig & _BODEN_OFF 
@ __config  MyConfig
'@ __CONFIG _HS_OSC & _WDT_ON & _PWRTE_ON  & _LVP_OFF & _CP_OFF
Define PIC16F877A
@ errorlevel -230
CMCON  = 7  
ADCON1 = 7 
define OSC 20
TrisD = %00000000

DEFINE LCD_DREG PORTA
    DEFINE LCD_DBIT 0
    DEFINE LCD_RSREG PORTA
    DEFINE LCD_RSBIT 5
    DEFINE LCD_EREG PORTA
    DEFINE LCD_EBIT 4
    DEFINE LCD_BITS 4
    DEFINE LCD_LINES 4

    include "keypad.bas"
pause 1000
lcdout 254,1
lcdout 254,128,"PIC Self Test"
pause 1000
    
    DEFINE KEYPAD_ROW        4        ' 4 ROW keypad       
    DEFINE KEYPAD_ROW_PORT   PORTB    ' ROW port = PORTB
    DEFINE KEYPAD_ROW_BIT    4        ' ROW0 = PORTB.4
    DEFINE KEYPAD_COL        4        ' 3 COL keypad
    DEFINE KEYPAD_COL_PORT   PORTB    ' COL port = PORTB
    DEFINE KEYPAD_COL_BIT    0        ' COL0 = PORTB.1
    DEFINE KEYPAD_DEBOUNCEMS 50       ' debounce delay = 50 mSec
    DEFINE SCAN_ONCE         1

    OPTION_REG.7 = 0        ' Enable internal crap pull-up :D

    PORTB = 0             '  
    TRISB = %11110000     '
    Flags = 0  
    ByteA var byte         '
    Combocount var byte 
        INTCON = %10001000    ' Enable global interrupt
                          ' Enable interrupt on PORTB change
    on interrupt goto KeypadInt
    CLEAR

Portd.2 = 0
combocount = 0

Init:    
    lcdout $FE,1,"Press any Key"
 disable
KeypadINT:    
@ READKEYPAD _ByteA
    TRISB=%11110000
    PORTB=0
    INTCON.0=0
    resume
enable   
    
    
Start:
    if ByteA then
    If ByteA = 4  then ByteA = "A"
    if ByteA = 5  then ByteA = 4
    if ByteA = 6  then ByteA = 5
    if ByteA = 7  then ByteA = 6
    if ByteA = 8  then ByteA = "B"
    if ByteA = 9  then ByteA = 7
    if ByteA = 10 then ByteA = 8
    if ByteA = 11 then ByteA = 9
    if ByteA = 12 then ByteA = "C"
    if ByteA = 13 then ByteA = "*"
    if ByteA = 14 then ByteA = 0
    if ByteA = 15 then ByteA = "#"
    if ByteA = 16 then ByteA = "D"
    if ByteA != 0 then  gosub combo
        
        ByteA = 0
        pause 1000
        goto init
        'else
           
else   
endif
goto start

combo:
    IF (combocount = 0) and (ByteA = 7)   then GoodKey
    IF (combocount = 1) and (ByteA = 8)   then GoodKey
    IF (combocount = 2) and (ByteA = "A") then GoodKey
    IF (combocount = 3) and (ByteA = 5)   then GoodKey
    IF (combocount = 4) and (ByteA = "D") then GoodKey
    combocount = 0 ; invalid keypress
return

GoodKey:
    combocount = combocount + 1
    if combocount = 5 then GrantAccess
return
goto init ' Combination 78A5D


GrantAccess:
hight portd.2
pause 1000
low portd.2
pause 1000

ByteA = 0
Combo1 = 0


end

No Leonardo,
Use the code Darrel posted in post #9 above, or the version of it, I sent you.
JS

**Archangel** · - 13th February 2007, 22:41

As this is my first venture into eprom, and I understand how to change the value and number of digits prior to compiling, my question is this: once the chip is programmed, is the eprom value fixed, or can it be changed?

**Archangel** · - 13th February 2007, 22:33

Originally Posted by Darrel Taylor

You should run the program in MCSP debugger and watch what happens. After watching debuggers for awhile, you'll be able to see it in your mind, and programming will go a lot smoother. And eventually, you won't even need the debugger anymore, or the PIC. It'll run inside your head.

I will have to make that purchase, as I have only the freebie version which was included with PBP, as you recommend it, it must be worthwhile.
Do you relize the power of this project? I am using it to operate the alarm on my mother's garage, another user here, for whom this was all about is using it for his gate, and it occured to me it is a useful tool to secure the table saw, bandsaw etc . . . from the children, or even adults! So since I do not have an address to send you some beer, i give you this, the knowledge that your efforts may save some little fingers.
JS

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