mirror of
git://sigrok.org/libserialport
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250 lines
8.9 KiB
Plaintext
250 lines
8.9 KiB
Plaintext
-------------------------------------------------------------------------------
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libserialport: cross-platform library for accessing serial ports
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-------------------------------------------------------------------------------
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libserialport is a minimal library written in C that is intended to take care
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of the OS-specific details when writing software that uses serial ports.
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By writing your serial code to use libserialport, you enable it to work
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transparently on any platform supported by the library.
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The operations that are supported are:
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- Port enumeration (obtaining a list of serial ports on the system).
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- Opening and closing ports.
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- Setting port parameters (baud rate, parity, etc).
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- Reading, writing and flushing data.
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- Obtaining error information.
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libserialport is an open source project released under the LGPL3+ license.
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Status
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======
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The library should build and work on any Windows or Unix-based system. If it
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does not, please submit a bug.
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Enumeration is currently only implemented on Windows, Mac OS X and Linux. On
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other systems enumeration will return no results, but ports can still be opened
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by name and then used.
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If you know how to enumerate available ports on another OS, please submit a bug
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with this information, or better still a patch implementing it.
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Future
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======
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Future versions will add additional API calls for obtaining metadata about a
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port, e.g. for USB devices the USB VID and PID of the underlying device.
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Dependencies
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============
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On Linux, libudev is required. On other systems no other libraries are required.
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The libudev dependency could be eliminated in favour of direct sysfs queries at
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the cost of some brevity. This is not currently a priority but if you feel like
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doing this feel free to submit a patch.
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Building
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========
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The package uses a GNU style build system and requires a Unix style shell.
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On Windows it can be built with the MinGW toolchain and MSYS environment.
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Run "./autogen.sh" to generate the build system, "./configure" to setup, then
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"make" to build the library and "make install" to install it.
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API
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===
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The API is simple, and designed to be a minimal wrapper around the serial port
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support in each OS.
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Most functions take a pointer to a struct sp_port, which represents a serial
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port. These structures are always allocated and freed by the library, using the
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functions in the 'Enumeration' section below.
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All functions can return only three possible error values. SP_ERR_ARG indicates
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the function was called with invalid arguments. SP_ERR_FAIL indicates that the
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OS reported a failure. SP_ERR_MEM indicates that a memory allocation failed.
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All of these error values are negative.
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When SP_ERR_FAIL is returned, an error code or string description of the error
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can be obtained by calling sp_last_error_code() or sp_last_error_message(). The
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error code or message is that provided by the OS; libserialport does not define
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any error codes or messages of its own.
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Function calls that succeed return SP_OK, which is equal to zero, or where
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otherwise documented a positive value.
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The available functions are as follows:
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Enumeration
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-----------
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int sp_get_port_by_name(const char *portname, struct sp_port **port_ptr);
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Obtains a pointer to a new sp_port structure representing the named port. The
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user should allocate a variable of type "struct sp_port *" and pass a pointer
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to this to receive the result.
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The result should be freed after use by calling sp_free_port().
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Returns: SP_OK on success, SP_ERR_FAIL on failure, SP_ERR_MEM on allocation
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failure, or SP_ERR_ARG if an invalid pointer is passed. If any error
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is returned, the variable pointed to by port_ptr will be set to NULL.
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Otherwise, it will be set to point to the newly allocated port.
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void sp_free_port(struct sp_port *port);
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Frees a port structure obtained from sp_get_port_by_name().
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int sp_list_ports(struct sp_port ***list_ptr);
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Lists the serial ports available on the system. The result obtained is an
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array of pointers to sp_port structures, terminated by a NULL. The user should
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allocate a variable of type "struct sp_port **" and pass a pointer to this to
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receive the result.
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The result should be freed after use by calling sp_free_port_list(). If a port
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from the list is to be used after freeing the list, it must be copied first
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using sp_copy_port().
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Returns: SP_OK on success, SP_ERR_FAIL on failure, SP_ERR_MEM on allocation
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failure, or SP_ERR_ARG if an invalid pointer is passed. If any error
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is returned, the variable pointed to by list_ptr will be set to NULL.
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Otherwise, it will be set to point to the newly allocated array.
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int sp_copy_port(const struct sp_port *port, struct sp_port **copy_ptr);
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Makes a new copy of a sp_port structure. The user should allocate a variable
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of type "struct sp_port *" and pass a pointer to this to receive the result.
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The copy should be freed after use by calling sp_free_port().
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Returns: SP_OK on success, SP_ERR_MEM on allocation failure, or SP_ERR_ARG
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if an invalid port or pointer is passed. If any error is returned,
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the variable pointed to by copy_ptr will be set to NULL. Otherwise,
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it will be set to point to the newly allocated copy.
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void sp_free_port_list(struct sp_port **list);
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Frees a port list obtained from sp_list_ports(). This will also free all
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the sp_port structures referred to from the list; any that are to be retained
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must be copied first using sp_copy_port().
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Opening and closing ports
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-------------------------
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int sp_open(struct sp_port *port, int flags);
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Opens the specified serial port.
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Parameters:
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port: Pointer to port structure.
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flags: Flags to use when opening the serial port. Possible
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flags are: SP_MODE_RDWR, SP_MODE_RDONLY, and SP_MODE_NONBLOCK.
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Returns: SP_OK on success, SP_ERR_FAIL on failure, SP_ERR_MEM on allocation
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failure, or SP_ERR_ARG if an invalid port is passed.
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int sp_close(struct sp_port *port);
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Closes the specified serial port.
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Returns: SP_OK on success, SP_ERR_FAIL on failure, or SP_ERR_ARG
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if an invalid port is passed.
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Setting port parameters
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-----------------------
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int sp_set_params(struct sp_port *port, int baudrate,
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int bits, int parity, int stopbits,
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int flowcontrol, int rts, int dtr);
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Sets serial parameters for the specified serial port.
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Parameters:
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port: Pointer to port structure.
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baudrate: Baud rate to set.
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bits: Number of data bits to use.
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parity: Parity setting to use
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(SP_PARITY_NONE, SP_PARITY_EVEN or SP_PARITY_ODD)
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stopbits: Number of stop bits to use (1 or 2).
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flowcontrol: Flow control setting to use
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(SP_FLOW_NONE, SP_FLOW_HARDWARE or SP_FLOW_SOFTWARE)
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Returns: SP_OK on success, SP_ERR_FAIL on failure, or SP_ERR_ARG
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for invalid arguments.
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Reading, writing and flushing data
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----------------------------------
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int sp_read(struct sp_port *port, const void *buf, size_t count)
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Reads bytes from the specified serial port. Note that this function may
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return after reading less than the specified number of bytes; it is the
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user's responsibility to iterate as necessary in this case.
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Parameters:
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port: Pointer to port structure.
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buf: Buffer in which to store the bytes read.
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count: Maximum number of bytes to read.
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Returns: The number of bytes read, SP_ERR_FAIL on failure,
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or SP_ERR_ARG for invalid arguments.
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int sp_write(struct sp_port *port, const void *buf, size_t count)
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Write bytes to the specified serial port. Note that this function may
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return after writing less than the specified number of bytes; it is the
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user's responsibility to iterate as necessary in this case.
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Parameters:
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port: Pointer to port structure.
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buf: Buffer containing the bytes to write.
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count: Maximum number of bytes to write.
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Returns: The number of bytes written, SP_ERR_FAIL on failure,
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or SP_ERR_ARG for invalid arguments.
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int sp_flush(struct sp_port *port);
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Flushes serial port buffers.
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Returns: SP_OK on success, SP_ERR_FAIL on failure, or SP_ERR_ARG
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if an invalid port is passed.
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Error handling
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--------------
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int sp_last_error_code();
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Gets the error code for a failed operation.
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In order to obtain the correct result, this function should be called
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straight after the failure, before executing any other system operations.
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Returns: The system's numeric code for the error that caused the last
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operation to fail.
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char *sp_last_error_message();
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Gets the error message for failed operation.
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In order to obtain the correct result, this function should be called
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straight after the failure, before executing other system operations.
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Returns: The system's message for the error that caused the last
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operation to fail. This string may be allocated by the function,
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and should be freed after use by calling sp_free_error_message.
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void sp_free_error_message(char *message);
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Frees the error message returned by sp_last_error_message().
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