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 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" ;
my $owserver = OWNet -> new( address ) ;
OWNet::read( address, path [,size [,offset]] ) $owserver -> read( path [,size [,offset]] )
OWNet::write( address, path, value [,offset] ) $owserver -> write( path, value [,offset] )
OWNet::dir( address, path ) $owserver -> dir( path )
TCP/IP address of owserver. Valid forms:
Additional arguments to add to address
Temperature scale can also be specified in the address. Same syntax as the other OWFS programs:
Pressure 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):
Show directories that are themselves directories with a '/' suffix ( e.g. /10.67C6697351FF/ )
Warning messages will only be displayed if verbose flag is specified in address
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"
New value for a device property. Used by write.
Object-oriented (only):
OWNet::new( address )
Create a new OWNet object -- corresponds to an owserver.
Error (and undef return value) if:
OWNet::read( address , path [ , size [ , offset ] ] )
$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:
OWNet::write( address , path , value [ , offset ] )
$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:
OWNet::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:
OWNet::present( address , path )
$ownet->present( path )
Test if a 1-wire device exists.
Error (and undef return value) if:
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 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.
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..
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.
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
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, '/' ) ;
literal sting for the IP address, in dotted-quad or host format. This property is also used to indicate a substantiated object.
string for the port number (or service name). Service name must be specified as :owserver or the like.
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 error messages? Set by "-v" in object invocation.
Add "/" to the end of directory entries. Set by "-slash" in object invocation.
Socket address (object) for communication. Stays defined for persistent connections, else deleted between calls.
State of socket connection (persistent means the same socket is used which speeds network communication).
owprotocol version number (currently 0)
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.
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. 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.
Sends a message to owserver. Formats in owserver protocol. If a persistent socket fails, retries after new socket created.
Reads a specified length from server
Reads whole packet from server, using _FromServerBinaryParse (first for header, then payload). Discards ping packets silently.
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)
Paul H Alfille paul.alfille@gmail.com
Support for proper timeout using the "select" function seems broken in perl. This might leave 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, and 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.