' =========================================================================
'   File....... SW21-EX14-Debounce.SXB
'   Purpose.... Simple digital clock with software multiplexing
'   Author..... (C) 2000 - 2005, Parallax, Inc.
'   E-mail..... support@parallax.com
'   Started.... 01 SEP 2005
'   Updated.... 23 MAR 2007 by TSaavik for SX28
' =========================================================================

' -----[ Program Description ]---------------------------------------------
' This program demonstrates the simultaneous debouncing of multiple inputs.
' The input subroutine is easily adjusted to handle any number of inputs.

'------{ Device Settings ]-------------------------------------------------

DEVICE 		SX28,TURBO,BANKS8,OSCHS3,SYNC,OPTIONX
FREQ            50_000_000
ID		"EX14"
IRC_CAL         IRC_SLOW

' -----[ I/O Definitions ]-------------------------------------------------

BtnBus          VAR     RB                     ' four inputs, pins 0 - 3

' -----[ Constants ]-------------------------------------------------------


' -----[ Variables ]-------------------------------------------------------

btns            VAR     Byte                     ' debounced inputs
idx             VAR     Byte                     ' loop counter


' -----[ Initialization ]-------------------------------------------------
PROGRAM Start
watch btns, 4, UBIN

' -----[Subs ]-------------------------------------------------------------

' -----[ Program Code ]----------------------------------------------------

Start:
  Tris_B = %00001111                            ' make 0-3 inputs
 
Main:
  DO
    GOSUB Get_Buttons                           ' get debounced inputs
    'DEBUG HOME,
    '      "Inputs = ", IBIN4 btns               ' display in binary mode
    BREAK    					' use "polling" mode to read btn state
    PAUSE 50
  LOOP

' -----[ Subroutines ]-----------------------------------------------------

Get_Buttons:
  btns = %1111                                  ' enable all four inputs
  FOR idx = 1 TO 5
    btns = btns & ~BtnBus                       ' test inputs
    PAUSE 5                                     ' delay between tests
  NEXT
  RETURN