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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