owcapi - Online in the Cloud

PROGRAM:

NAME

owcapi - easy C-language 1-wire interface

SYNOPSIS

libowcapi library to link with your program

Initialization
ssize_t OW_init( device name or full parameter string )
ssize_t OW_init_args( int argc, char ** args )

The full set of initialization options is extensive. They correspond roughly to the
command line options of owfs (1) owhttpd (1) and owftpd (1)

Get data
int OW_present( const char * path )
int OW_get( const char * path, char ** buffer, size_t * buffer_length )
ssize_t OW_lread( const char * path, unsigned char * buffer, const size_t size, const
off_t offset )

Set data
ssize_t OW_put( const char * path, const char * buffer, size_t * buffer_length )
ssize_t OW_lwrite( const char * path, const unsigned char * buffer, const size_t size,
const off_t offset )

Debug
void OW_set_error_level( const char *param )
void OW_set_error_print( const char *param )

Close
void OW_finish( void )

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_present
OW_present is used to check presence of a 1-wire device.

Arguments
path is the path to the directory or file (property).

Returns
0 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_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_set_error_level
OW_set_error_level sets the debug output to a certain level. 0 is default, and higher
value gives more output.
(0=default, 1=err_connect, 2=err_call, 3=err_data, 4=err_detail, 5=err_debug,
6=err_beyond)

Arguments
params is the level. Should be an integer.

Returns
None

Sequence
One of the init functions must be called before setting the level, since init
defaults to level 0.

OW_set_error_print
OW_set_error_print sets where the debug output should be directed. 0=mixed output,
1=syslog, 2=console.

Arguments
params is the level. Should be an integer between 0 and 2.

Returns
None

Sequence
One of the init functions must be called before setting the level, since init
defaults to 0 (mixed output).

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 <owcapi.h>
unsigned char * buf;
size_t s ;
OW_init("/dev/ttyS0");
OW_set_error_print("2");
OW_set_error_level("6");
OW_get("/",&buf,&s) ;
printf("Directory %s0,buf);
free(buf);
OW_finish() ;

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