Listing 2—The algorithm for receiving a bit looks for a rising edge and measures the time to the next edge. Pulse duration discriminates the resulting logic value. The routine can also return a third value (BIT_INVALID) in case of inconsistent timing during the process. The code is independent of the input processing implementation hidden behind the function pair is_zero() and is_one(). 
static T_ZERO_ONE_INVALID receive_bit( void )
{
	unsigned long ticks;
	unsigned int  duration;

	Timer16_restart();
	while( is_zero() )
	{ 	if ( timeout )
			return( BIT_INVALID );
	};	

	Timer16_restart();
	while( is_one())
	{ 	if ( timeout )
			return( BIT_INVALID );
	}	
	while( is_zero() )
	{ 	if ( timeout )
			return( BIT_INVALID );
	}	
	ticks = ( TICKS_TIMEOUT - Timer16_wReadTimer() );
	Timer16_Stop();
	duration = ( ticks * 1000L ) / Timer16_FREQ;

	if ( duration < MIN_DURATION )
		return BIT_INVALID;
	
	if ( duration < MAX_SHORT_DURATION )
		return BIT_ONE;
	
		else
		return BIT_ZERO;
}