The 1-Wire bus from Dallas Semiconductor is very suitable for use in a small (home) network with various switches, sensors and actuators. The simplicity of the hardware is in sharp contrast to the complexity of the protocol on this bus, but fortunately this problem has been solved by the manufacturer with dedicated interface ICs and software that simplifies the communication between the PC and 1-Wire devices.Last April we published a design for a serial interface for the PC, which made it possible to communicate with devices on the 1-Wire bus using development software supplied by Dallas Semiconductor. This month we have an almost identical circuit, but for use with the USB port (USB = Universal Serial Bus). This port is beginning to be used more frequently for connecting peripherals to PCs and Macs. The serial port has now fallen out of favour in that respect. Some people are of the opinion that the trusty old RS232 interface will soon disappear from the PC and certainly from modern laptops. The future will tell if they’re right.