' ------------------------------------- RC switch -------------------------------------

' Uses 1-2mSec RC PWM signal to trigger 2 power FET's to control auxilliary functions
' in an RC car, boat or airplane. Uses PICAXE 08M2

' OUTL and OUTR have pull down resistors (no accidental firing) and drive N channel
' power FET's. These can be controlled individually from the RC transmitter, for lighting,
' dropoff of sweets, or for launching rockets (fireworks).

' the software has 2 modes
'
' learning mode -----------------------------------------------------------------------------
' at powerup OUTL and OUTR serve as configuration pins. When one of these pins is
' connected to Vcc, then the software reads the PWM value from the RC receiver and
' stores it in EEprom. From now on it will use this value as a trigger for this switch channel.
' method: set controls at RC transmitter in correct setting for channel L. Set OUTL high (jumper).
' Now Power on RC receiver and RC switch. Wait 2 seconds (to learn PWM). switch off receiver
' and RC switch. Repeat procedure for channel R.
' please be aware that during learning mode the power FET's will be ON.

' operating mode ---------------------------------------------------------------------------
' in this mode the RC switch listens to the PWM signal from the RC receiver.
' When it receives a PWM that is withing +/- 20uSec in pulse width identical to the stored
' value in EEprom, it switches ON the associated power FET (and switches off the other one).
' in all other PWM values both FET's are off.

' PICAXE08M2
' +----_----+
' +5V +1 8+ GND
' NC +2 7+ NC
' NC +3 6+ 1 OUTL
' PWM 3 +4 5+ 2 OUTR
' +---------+

' version control
' 0.1 pwmin, detect at fixed levels
' 0.2 jumpers on out1 and out2 used to program values in eeprom. no jumper = run
' potmeter is not being used anymore, but jumpers
' 0.3 jumpers inverted to prevent accidental firing during initialization with pull ups.
' lost 2 rockets because of this flaw....

Init:
'set outputs OUTL and OUTR to INPUT mode to check if learning mode is required
input 1
input 2

CheckMode:
'check if we need to calibrate, or execute
'the outputs are at this moment still inputs and pulled low (pulldown)
'unless config jumper to Vcc is placed

pause 250 ' time to settle inputs this pause also
' minimizes EEprom writes by slowing
' the read PWM - write EEprom loop.
if pin1=1 then CalPinL ' OUTL is Vcc
if pin2=1 then CalPinR ' OUTR is Vcc

pause 250
low 1 ' both FET's off
low 2
goto RunMode

CalPinL:
pulsin C.3,1,w1 ' get pwm input for L
write 1,b2 ' store value for L in mem 1 (b2 is low byte of w1)
goto CheckMode

CalPinR:
pulsin C.3,1,w1 ' get pwm input for R
write 2,b2 ' store value for R in mem 2 (b2 is low byte of w1)
goto CheckMode

RunMode:
pulsin C.3,1,w1 ' get pwm input
w1 = w1 + 2 ' prepare for jitter window +2 / -2
b4 = 0

read 1, b1 ' compare pwm to value for L with threshold +/- 2
b1 = w1 - b1
if b1 < 4 then
high 1 ' on L
low 2 ' off R
b4 = 1 ' note we fire
end if

read 2, b1 ' compare pwm to value for R with threshold +/- 2
b1 = w1 - b1
if b1 < 4 then
high 2 ' on R
low 1 ' off L
b4 = 1 ' note we fire
end if

if b4 = 0 then ' check if no fire trigger
low 1 ' off L
low 2 ' off R
end if

pause 100 ' here we skip up to 5 PWM cycles, but not critical
' for the application
goto RunMode