' =========================================================================
'
'   File...... VEX_Analog_to_Digital.SXB
'   Purpose... 12 channel digital demodulator for VEX receiver
'   Author.... T'Saavik (based on example code by Jon Williams)
'              Please do not contact Mr. Williams for support with this branch.
'   E-mail.... sxb@hellspark.com
'   Started... 02 MAR 2007
'   Updated... 09 SEPT 2008
'   Updated... 05 APRIL 2011 (added maxwords to PPM loops preventing outputs
'                             from becoming stuck on a loss of communications
'                             with the VEX controller. (unpluged/etc).
'
' =========================================================================


' -------------------------------------------------------------------------
' Program Description
' -------------------------------------------------------------------------
'
' Simple program to convert PPM stream from VEX RC receiver to 12 digital outs
'
' See: http://forums.parallax.com/forums/default.aspx?f=7&m=175498 
' and  http://www.vexfan.com/viewtopic.php?t=227
'


' -------------------------------------------------------------------------
' Conditional Compilation Symbols
' -------------------------------------------------------------------------

'{$DEFINE Test_Mode_OFF}


' -------------------------------------------------------------------------
' Device Settings
' -------------------------------------------------------------------------

DEVICE          SX28, OSCHS1, TURBO, STACKX, OPTIONX, BOR42
FREQ            50_000_000
ID              "VexAtoD"


' -------------------------------------------------------------------------
' IO Pins
' -------------------------------------------------------------------------

PPM		PIN	RA.0 INPUT		' PPM in (pull-up w/10k)

Controls	PIN	RBC   OUTPUT
Control0	PIN	RB.0 
Control1	PIN	RB.1 
Control2	PIN	RB.2 
Control3	PIN	RB.3 
Control4	PIN	RB.4			' digital control pins
Control5	PIN	RB.5

Control6	PIN	RC.0
Control7	PIN	RC.1
Control8	PIN	RC.2
Control9	PIN	RC.3
Control10	PIN	RC.4
Control11	PIN	RC.5

' -------------------------------------------------------------------------
' Constants
' -------------------------------------------------------------------------

IsOn		CON	1
MaxWord  con   65535

' -------------------------------------------------------------------------
' Variables
' -------------------------------------------------------------------------

pulseTmr	VAR	Word


' =========================================================================
  PROGRAM Start
' =========================================================================


' -------------------------------------------------------------------------
' Subroutine Declarations
' -------------------------------------------------------------------------


' -------------------------------------------------------------------------
' Program Code
' -------------------------------------------------------------------------

Start:
  Controls = %0000000000000000

Wait_For_Sync:
'{$IFDEF Test_Mode}
' since we are waiting here anyways, might as well do the break here
  WATCH pulseTmr
  WATCH Controls,16,UBIN
  BREAK
'{$ENDIF}

  pulseTmr = 0
  DO WHILE PPM = 0
    PAUSEUS 1
    INC pulseTmr
  IF pulseTmr = MaxWord THEN controls=%0000000000000000  ' If we lose vex connection, disable outputs
  LOOP
  IF pulseTmr < 4000 THEN Wait_For_Sync

Main:
controls=%0000000000000000

Ctrl_Port0:
  DO WHILE PPM = 1				' complete framing pulse
  LOOP
  pulseTmr = 0
  DO WHILE PPM = 0				' measure timing pulse
    PAUSEUS 5
    INC pulseTmr
    IF pulseTmr = MaxWord THEN controls=%0000000000000000  ' If we lose vex connection, disable outputs
  LOOP
  IF pulseTmr < 150 THEN			' short pulse?
    Control0 = IsOn
  ELSE
    IF pulseTmr > 250 THEN			' long pulse?
      Control6 = IsOn
    ENDIF
  ENDIF


Ctrl_Port1:
  DO WHILE PPM = 1				' complete framing pulse
  LOOP
  pulseTmr = 0
  DO WHILE PPM = 0				' measure timing pulse
    PAUSEUS 5
    INC pulseTmr
    IF pulseTmr = MaxWord THEN controls=%0000000000000000  ' If we lose vex connection, disable outputs
  LOOP
  IF pulseTmr < 150 THEN			' short pulse?
    Control1 = IsOn
  ELSE
    IF pulseTmr > 250 THEN			' long pulse?
      Control7 = IsOn
    ENDIF
  ENDIF

Ctrl_Port2:
  DO WHILE PPM = 1				' complete framing pulse
  LOOP
  pulseTmr = 0
  DO WHILE PPM = 0				' measure timing pulse
    PAUSEUS 5
    INC pulseTmr
    IF pulseTmr = MaxWord THEN controls=%0000000000000000  ' If we lose vex connection, disable outputs
  LOOP
  IF pulseTmr < 150 THEN			' short pulse?
    Control2 = IsOn
  ELSE
    IF pulseTmr > 250 THEN			' long pulse?
      Control8 = IsOn
    ENDIF
  ENDIF

Ctrl_Port3:
  DO WHILE PPM = 1				' complete framing pulse
  LOOP
  pulseTmr = 0
  DO WHILE PPM = 0				' measure timing pulse
    PAUSEUS 5
    INC pulseTmr
    IF pulseTmr = MaxWord THEN controls=%0000000000000000  ' If we lose vex connection, disable outputs
  LOOP
  IF pulseTmr < 150 THEN			' short pulse?
    Control3 = IsOn
  ELSE
    IF pulseTmr > 250 THEN			' long pulse?
      Control9 = IsOn
    ENDIF
  ENDIF

Ctrl_Port4:
  DO WHILE PPM = 1				' complete framing pulse
  LOOP
  pulseTmr = 0
  DO WHILE PPM = 0				' measure timing pulse
    PAUSEUS 5
    INC pulseTmr
    IF pulseTmr = MaxWord THEN controls=%0000000000000000  ' If we lose vex connection, disable outputs
  LOOP
  IF pulseTmr < 150 THEN			' short pulse?
    Control4 = IsOn
  ELSE
    IF pulseTmr > 250 THEN			' long pulse?
      Control10 = IsOn
    ENDIF
  ENDIF

Ctrl_Port5:
  DO WHILE PPM = 1				' complete framing pulse
  LOOP
  pulseTmr = 0
  DO WHILE PPM = 0				' measure timing pulse
    PAUSEUS 5
    INC pulseTmr
    IF pulseTmr = MaxWord THEN controls=%0000000000000000  ' If we lose vex connection, disable outputs
  LOOP
  IF pulseTmr < 150 THEN			' short pulse?
    Control5 = IsOn
  ELSE
    IF pulseTmr > 250 THEN			' long pulse?
      Control11 = IsOn
    ENDIF
  ENDIF

  GOTO Wait_For_Sync

' -------------------------------------------------------------------------
' Subroutine Code
' -------------------------------------------------------------------------


' =========================================================================
' User Data
' =========================================================================