16 bit PC Serial Port Receiver

This circuit was designed to control a 32 channel Christmas light show from the PC serial port. Originally designed with TTL logic, it has been simplified using CMOS circuits to reduce component count. It is a fairly simple, reliable circuit that requires only 4 common CMOS chips (for 8 outputs), an optical isolator, and a few discrete components. The schematic diagram (SERIAL.GIF) illustrates the circuit with 16 outputs which can be expanded with additional 8 bit shift registers.