"Onewire Optocoupler" is a small firmware for Atmel AVR microcontrollers which makes it act as a read/write data separator for the Dallas/Maxim Onewire bus system. This can be used for creating an opto-isolated onewire bus, where the host interface hasn't built-in opto-isolation, e.g. the popular DS9490 USB adaptor. It's also possible to isolate bus segments from each other. Unlike existing solutions, only a minimum number of easy to get electronic components are required.