\section{1-Wire Unit} The 1-Wire unit implements the Dallas Semiconductor's 1-Wire protocol, most commonly used to interface smart thermometers (DS18x20). The protocol is explained in section \ref{sec:theory-1wire}. This unit implements the ROM Search algorithm that is used to find the ROM codes of all 1-Wire devices connected to the bus. The algorithm can find up to 32 devices in one run; More devices can be found by issuing the SEARCH\_CONTINUE command. Devices are addressed using their ROM codes, unique 64-bit (8-byte) identifiers that work as addresses. When only one device is connected, the value 0 may be used instead and the addressing will be skipped. Its ROM code may be recovered using the READ\_ADDR command or by the search algorithm. \subsection{1-Wire Configuration} \begin{inicode} [1WIRE:ow@7] # Data pin pin=A0 # Parasitic (bus-powered) mode parasitic=N \end{inicode} \subsection{1-Wire Commands} \begin{cmdlist} 0 & \cname{CHECK\_PRESENCE} Test if there are any devices attached to the bus. & \begin{cmdresp} \cfield{u8} presence detected (0, 1) \end{cmdresp} \\ 1 & \cname{SEARCH\_ADDR} Start the search algorithm. & \begin{cmdresp} \cfield{u8} should continue (0, 1) \cfield{u64[]} ROM codes \end{cmdresp} \\ 2 & \cname{SEARCH\_ALARM} Start the search algorithm, finding only devices in an alarm state. & \begin{cmdresp} \cfield{u8} should continue (0, 1) \cfield{u64[]} ROM codes \end{cmdresp} \\ 3 & \cname{SEARCH\_CONTINUE} Continue a previously started search & \begin{cmdresp} \cfield{u8} should continue (0, 1) \cfield{u64[]} ROM codes \end{cmdresp} \\ 4 & \cname{READ\_ADDR} Read a device address (single device only) & \begin{cmdresp} \cfield{u64} ROM code \end{cmdresp} \\ 10 & \cname{WRITE} Write bytes to a device. & \begin{cmdreq} \cfield{u64} ROM code \cfield{u8[]} bytes to write \end{cmdreq} \\ 11 & \cname{READ} Write a request and read response. & \begin{cmdreq} \cfield{u64} ROM code \cfield{u16} read length \cfield{u8} verify checksum (0, 1) \cfield{u8[]} request bytes \end{cmdreq} \cjoin \begin{cmdresp} \cfield{u8[]} read bytes \end{cmdresp} \\ 20 & \cname{POLL\_FOR\_1} Wait for a READY status, used by DS18x20. Not available in parasitic mode. Responds with SUCCESS after all devices are ready. & \\ \end{cmdlist}