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PROGRAM:
NAME
ownet , (libownet) - easy C-language 1-wire interface to the owserver protocol
SYNOPSIS
libownet library to link with your program
Handle
OWNET_HANDLE
Handle to each owserver connection
Initialization
OWNET_HANDLE OWNET_init( const char * owserver_tcp_address_and_port )
Associate an owserver (1) tcp/ip address with a handle.
Directory listing
int OWNET_dirlist( OWNET_HANDLE owserver_handle , const char * onewire_path , char **
comma_separated_list )
Create a comma-separated list of directory elements.
int OWNET_dirprocess( OWNET_HANDLE owserver_handle , const char * onewire_path , void (*
dirfunc ) (void *, const char *), void * passed_on_value )
void dirfunc ( void * passed_on_value , const char * directory_element )
Apply function dirfunc to each directory element, along with an arbitrary passed_on_value.
Get data
int OWNET_read( OWNET_HANDLE owserver_handle , const char * onewire_path , const char **
return_string )
Read a value (of specified size) from a 1-wire device.
int OWNET_lread( OWNET_HANDLE owserver_handle , const char * onewire_path , const char **
return_string , size_t size , off_t offset )
Read a value (of specified size and offset) from a 1-wire device.
int OWNET_present( OWNET_HANDLE owserver_handle , const char * onewire_path )
Check if a 1-wire device is present.
Set data
int OWNET_put( OWNET_HANDLE owserver_handle , const char * onewire_path , const char *
value_string , size_t size )
Write a value (of specified size) to a 1-wire device.
int OWNET_lwrite( OWNET_HANDLE owserver_handle , const char * onewire_path , const char *
value_string , size_t size , off_t offset )
Write a value (of specified size and offset) to a 1-wire device.
Close
void OWNET_close( OWNET_HANDLE owserver_handle )
Close the connection to a particular owserver.
void OWNET_closeall( void )
Close all open owserver connections.
void OWNET_finish( void )
Close all open owserver connections and free all memory.
Temperature scale
void OWNET_set_temperature_scale( char temperature_scale )
char OWNET_get_temperature_scale( void )
Set and retrieve the temperature scale used for all communications.
Device format
void OWNET_set_device_format( const char * device_format )
const char * OWNET_get_device_format( void )
Set and retrieve the 1-wire device serial number format used for all communications.
FUNCTIONS
OW_init
OW_init_string offers the full flexibility of the owfs (1) and owhttpd (1) command line.
Arguments
Can be as simple as jus the device name, a full parameter specification. One or
more device names (includes tcp, serial, usb...) and command line switches. See
owfs (1) for full syntax.
Returns
0 for success. -1 on error and errno will be set. OW_finish does not need to be
called if OW_init fails.
Sequence
One of the init functions must be called before accessing the 1-wire bus.
OW_finish is optional.
OW_init_args
OW_init_args offers the full flexibility of the owfs (1) and owhttpd (1) command line.
Arguments
One or more device names (includes tcp, serial, usb...) and command line switches.
See owfs (1) for full syntax. Unlike OW_init_string the arguments are in argv/argc
format.
Returns
0 for success. -1 on error and errno will be set. OW_finish does not need to be
called if OW_init fails.
Sequence
One of the init functions must be called before accessing the 1-wire bus.
OW_finish is optional.
OW_get
OW_get is used to get directory listings and file contents. The results are put in a
dynamically allocated buffer.
Arguments
path is the path to the directory or file (property). *buffer returns a pointer to
a buffer containing the directory (comma separated) or value. buffer_length
returns the length of the value/string in buffer
Returns
number of bytes on success. -1 on error (and errno is set).
Sequence
One of the init functions must be called before accessing the 1-wire bus.
OW_finish is optional.
Important note
buffer is allocated ( with malloc ) by OW_get but must be freed in your program.
See malloc (3) and free (3)
OW_lread
OW_lread is used to read 1-wire memory chips. Think of it as a combination of lseek and
read It allows random-access to the memory, specifying location and length. Unlike OW_get
directories cannot be obtained and the buffer must be pre-allocated rather than allocated
by the routine. buffer must be at least size length.
Arguments
path is the path to the file (property). buffer is the (pre-allocated) memory area
where the value will be placed. size is the length of bytes requested. offset is
the position in file to start reading.
Returns
number of bytes on success. -1 on error (and errno is set).
Sequence
One of the init functions must be called before accessing the 1-wire bus.
OW_finish is optional.
OW_put
OW_put is an easy way to write to 1-wire chips.
Arguments
path is the path to the file (property). buffer is the value to be written.
buffer_length is the length of the value buffer. Returns number of bytes on
success. -1 on error (and errno is set).
Sequence
One of the init functions must be called before accessing the 1-wire bus.
OW_finish is optional.
OW_lwrite
OW_lwrite is the companion of OW_lread. It allows writing to arbitrary positions in
1-wire memory. Think of it as a combination of lseek and write. buffer must be at least
size length.
Arguments
path is the path to the file (property). buffer is the data to be written. size
is the length of bytes to be written. offset is the position in file to start
writing.
Returns
number of bytes on success. -1 on error (and errno is set).
Sequence
One of the init functions must be called before accessing the 1-wire bus.
OW_finish is optional.
OW_finish
OW_finish cleans up the OWFS 1-wire routines, releases devices and memory.
Arguments
None.
Returns
None
Sequence
OW_finish is optional since cleanup is automatic on program exit.
DESCRIPTION
1-Wire
1-wire is a wiring protocol and series of devices designed and manufactured by Dallas
Semiconductor, Inc. The bus is a low-power low-speed low-connector scheme where the data
line can also provide power.
Each device is uniquely and unalterably numbered during manufacture. There are a wide
variety of devices, including memory, sensors (humidity, temperature, voltage, contact,
current), switches, timers and data loggers. More complex devices (like thermocouple
sensors) can be built with these basic devices. There are also 1-wire devices that have
encryption included.
The 1-wire scheme uses a single bus master and multiple slaves on the same wire. The bus
master initiates all communication. The slaves can be individually discovered and
addressed using their unique ID.
Bus masters come in a variety of configurations including serial, parallel, i2c, network
or USB adapters.
OWFS design
OWFS is a suite of programs that designed to make the 1-wire bus and its devices easily
accessible. The underlying principle is to create a virtual filesystem, with the unique ID
being the directory, and the individual properties of the device are represented as simple
files that can be read and written.
Details of the individual slave or master design are hidden behind a consistent interface.
The goal is to provide an easy set of tools for a software designer to create monitoring
or control applications. There are some performance enhancements in the implementation,
including data caching, parallel access to bus masters, and aggregation of device
communication. Still the fundemental goal has been ease of use, flexibility and
correctness rather than speed.
libowcapi
libowcapi (1) is an encapsulation of the full libow library for C programs.
libowcapi (1) allows a C program to use OWFS principles (consistent naming scheme,
multiple adapters, devices, and compatibility) directly from a C program. There are
analogous modules for other programming languages:
C libowcapi
perl owperl
php owphp
python owpython
tcl owtcl
EXAMPLE
/* Simple directory listing -- no error checking */
#include <ownetapi.h>
char * buf;
size_t s ;
OWNET_init("localhost:4304");
OWNET_dirlist("/",&buf,&s) ;
printf("Directory %s0,buf);
free(buf);
OWNET_finish() ;
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