В DS написано:
Цитата
In the Single-Wire Interface mode, communications to and from the ATSHA204A take place over the SDA pin, a
single, asynchronously timed wire, and the SCL pin is ignored.
Note: The sleep current specification values are guaranteed only if the SCL pin is held low or left unconnected.
The overall communications structure is a hierarchy: The figure below shows how to uses the Single-Wire
Interface with a standard RS-232 port. The port should be set to 7-bit addressing and 230 baud.
Так что будет достаточно довольно тривиального переходника из RS232
А вот софт придется видимо писать самому