OWNet man page

OWNet — Light weight access to owserver

Synopsis

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 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_p…)

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/ow…
Location where source code is hosted.

Info

2010-06-15 perl v5.10.0 User Contributed Perl Documentation