Region buttons module

SelectLO: takes no arguments, returns nothing
	set select line LO

SelectHI: takes no arguments, returns nothing
	set select line HI

InitializeButtons: takes no arguments, returns nothing
	SelectLO
	set L1, L3, R1, R3 buttons to not pressed
	record last LO time
	SelectHI
	L2, L4, R2, R4 buttons to not pressed
	record last HI time
	SelectLO
	next sample state = LO

CheckButtonState: takes button index (0-7), returns	button state
	local variable return state
	if button index 0 or 1
		check if bit 5 HI, set value to return state
	if button index 2 or 3
		check if bit 4 HI, set value to return state
	if button index 4 or 5
		check if bit 3 HI, set value to return state
	if button index 6 or 7
		check if bit 2 HI, set value to return state
	if return state is nonzero
		return state == OFF (button not pressed)
	else
		return state = ON (button pressed)
	return return state

CheckButtonPress: takes no arguments, returns which button pressed (0-7)	
	local variables: current LO time, current HI time, button states = OFF, 
	return event = 0, current sample state = next sample state
	if current sample state is HI
		update current HI time
		if a debounce interval has expired
			update current button states
			if a button has been pressed down
				return event = which button changed
				update the last button state
			if a button has been released
				update the last button state
			update the last HI time
	if current sample state is LO
		update current LO time
		if a debounce interval has expired
			update current button states
			if a button has been pressed down
				return event = which button changed
				update the last button state
			if a button has been released
				update the last button state
			update the last LO time
	if current sample state is HI
		next sample state = LO
		SelectLO
	if current sample state is LO
		next sample state = HI
		SelectHI
	return return event