'  Name    : cam_switch_keep_alive.BAS                                   
'  Author  : Christopher Good                    
'  Notice  : Copyright (c) 2006                                
'          : All Rights Reserved                               
'  Date    : 3/2/2006                                          
'  Version : 1.0                                               
'  Notes   : Free source code. Compile with Proton IDE Lite (also free).  Program your PIC with IC-Prog (also free).
'		   This version does not monitor awake line; it takes a picture every 30 seconds to keep camera alive.                                              
' 
'          Pin8 = Ground                  - tie to common, connect to pin 1 via .1MF cap 
'          Pin7 = GPIO.0  - i/o           - not used
'          Pin6 = GPIO.1  - i/o           - LED - tie pin 6 to high side (anode) of led, tie led low side (cathode) through resistor to ground
'          Pin5 = GPIO.2  - i/o           - shutter - drive to ground to close shutter - connect to shutter switch
'          Pin4 = GPIO.3  - input only    - RC PWM signal - tie to RC signal via 4.7k ohm resistor
'          Pin3 = GPIO.4  - i/o           - not used
'          Pin2 = GPIO.5  - i/o           - not used
'          Pin1 = Vcc                     - tie to +5v, connect to pin 8 via .1MF cap


Device 12C508
Config INTRC_OSC, MCLRE_OFF, WDT_OFF, CP_OFF                           ' set config fuses
OPTION_REG.5 = 0                                                       ' clock source internal

Dim Pulselen   As Byte                                                 ' Pulselen can be 0 - 255, 100 = 1 ms, 200 = 2 ms
Dim Init       As Byte                                                 ' Init used to flash LED
Dim Waittime   As Word                                                 ' Waittime can be 0 - 32767
Dim State      As Byte                                                 ' State can be 0 - 4
Clear                                                                  ' set all variables = 0

Blink: 
   For Init = 1 To 3                                                   ' blink led 3 times
      High GPIO.1                                                      ' pin 6  - turn led on
      DelayMS 200                                                      ' wait 0.2 seconds
      Low GPIO.1                                                       ' pin 6  - turn led off
      DelayMS 200                                                      ' wait 0.2 seconds
   Next
		    
ReadPWM:
   Pulselen = PulsIn GPIO.3, High                                               ' pin 4 - read high pulse length, times out after .65535 seconds 
   DelayMS 15                                                                   ' delay 15 ms
   If Pulselen < 50                                   Then GoTo Blink           ' no signal  -> blink led again 
   If State = 0 And Pulselen > 75  And Pulselen < 125 Then State = 1            ' state 0 , low pulse  -> go to state 1
   If State = 1 And Pulselen > 175 And Pulselen < 225 Then State = 2            ' state 1 , high pulse -> go to state 2      
   If State = 2 And Pulselen > 75  And Pulselen < 125 Then State = 3            ' state 2 , low pulse  -> go to state 3
   If State = 3 And Pulselen > 75  And Pulselen < 125 Then GoTo waitcounter     ' state 3 , low pulse  -> waiting, increment wait counter
   If State = 3 And Pulselen > 175 And Pulselen < 225 Then GoTo takepicture     ' state 3 , high pulse -> take a picture
   If State = 4 And Pulselen > 75  And Pulselen < 125 Then State = 3            ' state 4 , low pulse  -> stick has toggled low, go to state 3
   If State = 4 And Pulselen > 175 And Pulselen < 225 Then GoTo waitcounter     ' state 4 , high pulse -> stick has not toggled low, increment wait counter
   GoTo ReadPWM                                                                 ' restart loop for all other possibilities
    
waitcounter:                                                            ' increment wait counter
   Waittime = Waittime + 1                                              ' + 1
   If Waittime > 900 Then GoTo takepicture                              ' if wait couter > timeout then take a picture to keep camera awake
   GoTo ReadPWM   
        
takepicture:                                                            ' take a picture
   Low GPIO.2                                                           ' pin 5 - drive it low - close the shutter
   High GPIO.1                                                          ' pin 6 - turn led on
   DelayMS 250                                                          ' keep shutter closed and LED on for 0.25 seconds
   Input GPIO.2                                                         ' pin 5 - set to tristate - high impedance
   Low GPIO.1                                                           ' pin 6 - turn led off
   Waittime = 0                                                         ' reset wait counter
   State = 4                                                            ' set state as picture taken
   DelayMS 3000                                                         ' wait 3 seconds for camera to store picture
   GoTo ReadPWM                                                         ' start it all again