Matrix keyboard for up to 32 keys

[Pedro Pinto]

Hello
For scan a keyboard with up to 16 keys we use this code from Melabs,
I need it for up to 32 keys. It is possible with this construct, and how?

Thanks
Regards
Pedro

' PicBasic Pro program to display key number on LCD
' Define LOADER_USED to allow use of the boot loader.
' This will not affect normal program operation.
Define	LOADER_USED	1

' Define LCD connections
Define  LCD_DREG        PORTD
Define  LCD_DBIT        4
Define  LCD_RSREG       PORTE
Define  LCD_RSBIT       0
Define  LCD_EREG        PORTE
Define  LCD_EBIT        1

' Define program variables
col     var     byte            ' Keypad column
row     var     byte            ' Keypad row
key     var     byte            ' Key value

        OPTION_REG.7 = 0        ' Enable PORTB pullups
        ADCON1 = 7              ' Make PORTA and PORTE digital
        Low PORTE.2             ' LCD R/W low (write)
        Pause 100               ' Wait for LCD to start
        Lcdout $fe, 1, "Press any key"  ' Display sign on message

loop:   Gosub getkey            ' Get a key from the keypad
        Lcdout $fe, 1, #key     ' Display ASCII key number
        Goto loop               ' Do it forever

' Subroutine to get a key from keypad
getkey:
        Pause 50                ' Debounce

getkeyu:
        ' Wait for all keys up
        PORTB = 0               ' All output pins low
        TRISB = $f0             ' Bottom 4 pins out, top 4 pins in
        If ((PORTB >> 4) != $f) Then getkeyu    ' If any keys down, loop

        Pause 50                ' Debounce

getkeyp:
        ' Wait for keypress
        For col = 0 to 3        ' 4 columns in keypad
                PORTB = 0       ' All output pins low
                TRISB = (dcd col) ^ $ff ' Set one column pin to output
                row = PORTB >> 4        ' Read row
                If row != $f Then gotkey        ' If any keydown, exit
        Next col
Goto getkeyp            ' No keys down, go look again

gotkey: ' Change row and column to key number 1 - 16
        key = (col * 4) + (ncd (row ^ $f))
        Return                  ' Subroutine over

        End

[Darrel Taylor]

Using mister-e's Matrix Keypad module you can have 64 keys if you want.
Requires 2 full 8-bit ports, 8 rows, 8 columns.

OR ... 8 rows, 4 columns = 32 keys
OR ... 4 rows, 8 columns

It's essentially an extension of the meLabs keypad example with more features.

Matrix Keypad routine
http://www.picbasic.co.uk/forum/showthread.php?t=3250
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