OWNet(3) User Contributed Perl Documentation OWNet(3)NAMEOWNet - Light weight access to owserver
SYNOPSISOWNet 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 its interesting devices. The One Wire File System (OWFS)
is a suite of programs that hide 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.
Example perl program that prints the temperature:
use OWNet ;
print OWNet::read( "localhost:4304" , "/10.67C6697351FF/temperature" ) ."\n" ;
There is the alternative object oriented form:
use OWNet ;
my $owserver = OWNet->new( "localhost:4304" ) ;
print $owserver->read( "/10.67C6697351FF/temperature" ) ."\n" ;
SYNTAX
methods
new
my $owserver = OWNet -> new( address ) ;
read
OWNet::read( address, path [,size [,offset]] )
$owserver -> read( path [,size [,offset]] )
write
OWNet::write( address, path, value [,offset] )
$owserver -> write( path, value [,offset] )
dir
OWNet::dir( address, path )
$owserver -> dir( path )
address
TCP/IP address of owserver. Valid forms:
name test.owfs.net:4304
quad number: 123.231.312.213:4304
host localhost:4304
port 4304
additional arguments
Additional arguments to add to address
Temperature scale can also be specified in the address. Same syntax as
the other OWFS programs:
-C Celsius (Centigrade)
-F Fahrenheit
-K Kelvin
-R Rankine
Pressure scale can also be specified in the address. Same syntax as the
other OWFS programs:
--mbar millibar (default)
--atm atmosphere
--mmHg mm Mercury
--inHg inch Mercury
--psi pounds per inch^2
--Pa pascal
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):
-ff.i /10.67C6697351FF (default)
-ffi /1067C6697351FF
-ff.i.c /10.67C6697351FF.8D
-ff.ic /10.67C6697351FF8D
-ffi.c /1067C6697351FF.8D
-ffic /1067C6697351FF8D
Show directories that are themselves directories with a '/' suffix (
e.g. /10.67C6697351FF/ )
-slash show directory elements
Warning messages will only be displayed if verbose flag is specified in
address
-v verbose
path
owfs-type path to an item on the 1-wire bus. Valid forms:
main directories
Used for the dir method. E.g. "/" "/uncached"
"/1F.321432320000/main"
device directory
Used for the dir and present method. E.g. "/10.4300AC220000"
"/statistics"
device properties
Used to read, write. E.g. "/10.4300AC220000/temperature"
value
New value for a device property. Used by write.
METHODS
new Object-oriented (only):
OWNet::new( address )
Create a new OWNet object -- corresponds to an owserver.
Error (and undef return value) if:
1 Badly formed tcp/ip address
2 No owserver at address
read
Non object-oriented:
OWNet::read( address , path [ , size [ , offset ] ] )
Object-oriented:
$ownet->read( path [ , size [ , offset ] ] )
Read the value of a 1-wire device property. Returns the (scalar
string) value of the property.
size (number of bytes to read) is optional
offset (number of bytes from start of field to start write) is
optional
Error (and undef return value) if:
1 (Non object) No owserver at address
2 (Object form) Not called with a valid OWNet object
3 Bad path
4 path not a readable device property
write
Non object-oriented:
OWNet::write( address , path , value [ , offset ] )
Object-oriented:
$ownet->write( path , value [ , offset ] )
Set the value of a 1-wire device property. Returns "1" on success.
offset (number of bytes from start of field to start write) is
optional
Error (and undef return value) if:
1 (Non object) No owserver at address
2 (Object form) Not called with a valid OWNet object
3 Bad path
4 path not a writable device property
5 value incorrect size or format
dir
Non object-oriented:
OWNet::dir( address , path )
Object-oriented:
$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:
1 (Non object) No owserver at address
2 (Object form) Not called with a valid OWNet object
3 Bad path
4 path not a directory
present (deprecated)
Non object-oriented:
OWNet::present( address , path )
Object-oriented:
$ownet->present( path )
Test if a 1-wire device exists.
Error (and undef return value) if:
1 (Non object) No owserver at address
2 (Object form) Not called with a valid OWNet object
3 Bad path
4 path not a device
DESCRIPTION
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 its 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. OWNet will use persistent tcp
connections for the object form -- potentially a performance boost over
a slow network.
EXAMPLES
owserver
owserver is a separate process that must be accessible on the network.
It allows multiple clients, and can connect to many physical 1-wire
adapters and 1-wire devices. It's address must be discoverable --
either set on the command line, or at it's default location, or by
using Bonjour (zeroconf) service discovery.
An example owserver invocation for a serial adapter and explicitly
chooses the default port:
owserver -d /dev/ttyS0 -p 4304
OWNet
use OWNet ;
# Create owserver object
my $owserver = OWNet->new('localhost:4304 -v -F') ; #default location, verbose errors, Fahrenheit degrees
# my $owserver = OWNet->new() ; #simpler, again default location, no error messages, default Celsius
#print directory
print $owserver->dir('/') ;
#print temperature from known device (DS18S20, ID: 10.13224366A280)
print "Temperature: ".$owserver->read('/uncached/10.13224366A280/temperature') ;
# Now for some fun -- a tree of everything:
sub Tree($$) {
my $ow = shift ;
my $path = shift ;
print "$path\t" ;
# first try to read
my $value = $ow->read($path) ;
if ( defined($value) ) {
print "$value\n";
return ;
}
# not readable, try as directory
my $dirstring = $ow->dir($path) ;
if ( defined($dirstring) ) {
print "<directory>\n" ;
my @dir = split /,/ , $ow->dir($path) ;
foreach (@dir) {
Tree($ow,$_) ;
}
return ;
}
# can't read, not directory
print "<write-only>\n" ;
return ;
}
Tree( $owserver, '/' ) ;
INTERNALS
Object properties (All private)
ADDR
literal sting for the IP address, in dotted-quad or host format.
This property is also used to indicate a substantiated object.
PORT
string for the port number (or service name). Service name must be
specified as :owserver or the like.
SG 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.
VERBOSE
Print error messages? Set by "-v" in object invocation.
SLASH
Add "/" to the end of directory entries. Set by "-slash" in object
invocation.
SOCK
Socket address (object) for communication. Stays defined for
persistent connections, else deleted between calls.
PERSIST
State of socket connection (persistent means the same socket is
used which speeds network communication).
VER owprotocol version number (currently 0)
Private methods
_self
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 properly 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.
_new
Takes command line invocation parameters (for an object or not) and
properly parses and sets up the properties in a hash array.
_Sock
Socket processing, including tests for persistence and opening. If
no host is specified, localhost (127.0.0.1) is used. If no port is
specified, uses the IANA allocated well known port (4304) for
owserver. First looks in /etc/services, then just tries 4304.
_ToServer
Sends a message to owserver. Formats in owserver protocol. If a
persistent socket fails, retries after new socket created.
_FromServerBinaryParse
Reads a specified length from server
_FromServer
Reads whole packet from server, using _FromServerBinaryParse (first
for header, then payload). Discards ping packets silently.
_BonjourLookup
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. (Uses the method
of http://sial.org/blog/2006/12/optional_perl_module_loading.html)
AUTHOR
Paul H Alfille paul.alfille@gmail.com
BUGS
Support for proper timeout using the "select" function seems broken in
perl. This might leave the routines vulnerable to network timing
errors.
SEE ALSO
http://www.owfs.org
Documentation for the full owfs program suite, including man pages
for each of the supported 1-wire devices, and more extensive
explanatation of owfs components.
http://owfs.sourceforge.net/projects/owfs
Location where source code is hosted.
COPYRIGHT
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.
perl v5.10.0 2010-06-15 OWNet(3)
