OWNet Light weight access to owserver OWNet is an easy way to access owserver and thence the 1-wire bus. Dallas Semiconductor's 1-wire system uses simple wiring and unique addresses for it's interesting devices. The One Wire File System is a suite of programs that hides 1-wire details behind a file system metaphor. owserver connects to the 1-wire bus and provides network access. OWNet is a perl module that connects to owserver and allows reading, writing and listing the 1-wire bus. For instance if we start owserver with: owserver -d /dev/ttyS0 -p 3000 Serial 1-wire adapter attached to a 1-wire bus with a DS18S20 temperature sensor. Then the following perl program prints the temperature: use OWNet ; print OWNET::read( "localhost:3000" , "/10.67C6697351FF/temperature" ) ."\n" ; There is the alternative object oriented form: use OWNet ; my $owserver = OWNET->new( "localhost:3000" ) ; print $owserver->read( "/10.67C6697351FF/temperature" ) ."\n" ;

methods
my $ownet = OWNet::new( address ) ; read( address , path ) $ownet->read( path ) write( address , path , value ) $ownet->write( path , value ) dir( address , path ) $ownet->dir( path ) present( address , path ) $ownet->present( path )

address
TCP/IP address of owserver. Valid forms: Temperature scale can also be specified in the address. Same syntax as the other OWFS programs: Device display format (1-wire unique address) can also be specified in the address, with the general form of -ff[.]i[[.]c] (family id crc): Warning messages will only be display if verbose flag is specified in address

path
owfs-type path to an item on the 1-wire bus. Valid forms: Used for the dir method. E.g. "/" "/uncached" "/1F.321432320000/main" Used for the dir and present method. E.g. "/10.4300AC220000" "/statistics" Used to read, write. E.g. "/10.4300AC220000/temperature"

value
New value for a device property. Used by write. new( address ) Create a new OWNet object -- corresponds to an owserver. Error (and undef return value) if: read( address , path ) $ownet->read( path ) Read the value of a 1-wire device property. Returns the (scalar string) value of the property. Error (and undef return value) if: write( address , path , value ) $ownet->write( path , value ) Set the value of a 1-wire device property. Returns "1" on success. Error (and undef return value) if: present( address , path ) $ownet->present( path ) Test if a 1-wire device exists. Error (and undef return value) if: dir( address , path ) $ownet->dir( path ) Return a comma-separated list of the entries in path. Entries are equivalent to "fully qualified names" -- full path names. Error (and undef return value) if:

OWFS
OWFS is a suite of programs that allows easy access to Dallas Semiconductor's 1-wire bus and devices. OWFS provides a consistent naming scheme, safe multplexing of 1-wire traffice, multiple methods of access and display, and network access. The basic OWFS metaphor is a file-system, with the bus beinng the root directory, each device a subdirectory, and the the device properties (e.g. voltage, temperature, memory) a file.

1-Wire
1-wire is a protocol allowing simple connection of inexpensive devices. Each device has a unique ID number (used in it's OWFS address) and is individually addressable. The bus itself is extremely simple -- a data line and a ground. The data line also provides power. 1-wire devices come in a variety of packages -- chips, commercial boxes, and iButtons (stainless steel cans). 1-wire devices have a variety of capabilities, from simple ID to complex voltage, temperature, current measurements, memory, and switch control.

Programs
Connection to the 1-wire bus is either done by bit-banging a digital pin on the processor, or by using a bus master -- USB, serial, i2c, parallel. The heavy-weight OWFS programs: owserver owfs owhttpd owftpd and the heavy-weight perl module OW all link in the full OWFS library and can connect directly to the bus master(s) and/or to owserver. OWNet is a light-weight module. It connects only to an owserver, does not link in the OWFS library, and should be more portable..

Object-oriented
OWNet can be used in either a classical (non-object-oriented) manner, or with objects. The object stored the ip address of the owserver and a network socket to communicate.

Object properties (All private)
literal sting for the IP address, in ip:port format. This property is also used to indicate a substantiated object. Flag sent to server, and returned, that encodes temperature scale and display format. Persistence is also encoded in this word in the actual tcp message, but kept separately in the object. Print errors? Corresponds to "-v" in object invocation. Socket address (object) for communication. Stays defined for persistent connections, else deleted between calls.

Private methods
Takes either the implicit object reference (if called on an object) or the ip address in non-object format. In either case a socket is created, the persistence bit is property set, and the address parsed. Returns the object reference, or undef on error. Called by each external method (read,write,dir) on the first parameter. Takes command line invocation parameters (for an object or not) and properly parses and sets up the properties in a hash array. Socket processing, including tests for persistence, and opening. Sends formats and sends a message to owserver. If a persistent socket fails, retries after new socket created. Reads a specified length from server Reads whole packet from server, usung _FromServerLow (first for header, then payload/tokens). Discards ping packets silently. Uses the IANA allocated well known port for owserver. First looks in /etc/services, then just tries 4304. Uses the mDNS service discovery protocol to find an available owserver. Employs NET::Rendezvous (an earlier name or Apple's Bonjour) This module is loaded only if available using the method of http://sial.org/blog/2006/12/optional_perl_module_loading.html Bounjour details for owserver at: Paul H Alfille paul.alfille @ gmail . com Support for proper timeout using the "select" function seems broken in perl. This leaves the routines vulnerable to network timing errors. Documentation for the full owfs program suite, including man pages for each of the supported 1-wire devices, nand more extensive explanatation of owfs components. Location where source code is hosted. Copyright (c) 2007 Paul H Alfille. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.