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2 libserialport: cross-platform library for accessing serial ports
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5 libserialport is a minimal library written in C that is intended to take care
6 of the OS-specific details when writing software that uses serial ports.
8 By writing your serial code to use libserialport, you enable it to work
9 transparently on any platform supported by the library.
11 The operations that are supported are:
13 - Port enumeration (obtaining a list of serial ports on the system).
14 - Opening and closing ports.
15 - Setting port parameters (baud rate, parity, etc).
16 - Reading, writing and flushing data.
17 - Obtaining error information.
19 libserialport is an open source project released under the LGPL3+ license.
24 The library should build and work on any Windows or Unix-based system. If it
25 does not, please submit a bug.
27 Enumeration is currently only implemented on Windows, Mac OS X and Linux. On
28 other systems enumeration will return no results, but ports can still be opened
29 by name and then used.
31 If you know how to enumerate available ports on another OS, please submit a bug
32 with this information, or better still a patch implementing it.
37 Future versions will add additional API calls for obtaining metadata about a
38 port, e.g. for USB devices the USB VID and PID of the underlying device.
43 On Linux, libudev is required. On other systems no other libraries are required.
45 The libudev dependency could be eliminated in favour of direct sysfs queries at
46 the cost of some brevity. This is not currently a priority but if you feel like
47 doing this feel free to submit a patch.
52 The package uses a GNU style build system and requires a Unix style shell.
53 On Windows it can be built with the MinGW toolchain and MSYS environment.
55 Run "./autogen.sh" to generate the build system, "./configure" to setup, then
56 "make" to build the library and "make install" to install it.
61 The API is simple, and designed to be a minimal wrapper around the serial port
64 Most functions take a pointer to a struct sp_port, which represents an serial
65 port. This structure is obtained from the array returned by sp_list_ports().
67 All functions can return only three possible error values. SP_ERR_ARG indicates
68 the function was called with invalid arguments. SP_ERR_FAIL indicates that the
69 OS reported a failure. SP_ERR_MEM indicates that a memory allocation failed.
70 All of these error values are negative.
72 When SP_ERR_FAIL is returned, an error code or string description of the error
73 can be obtained by calling sp_last_error_code() or sp_last_error_message(). The
74 error code or message is that provided by the OS; libserialport does not define
75 any error codes or messages of its own.
77 Functions calls that succeed return SP_OK, which is equal to zero, or where
78 otherwise documented a positive value.
80 The available functions are as follows:
85 int sp_get_port_by_name(const char *portname, struct sp_port **port_ptr);
87 Obtains a pointer to a new sp_port structure representing the named port. The
88 user should allocate a variable of type "struct sp_port *" and pass a pointer
89 to this to receive the result.
91 Returns: SP_OK on success, SP_ERR_FAIL on failure, SP_ERR_MEM on allocation failure,
92 or SP_ERR_ARG if an invalid pointer is passed. If any error is returned,
93 the value pointed to by port_ptr will be set to NULL.
95 void sp_free_port(struct sp_port *port);
97 Frees a port structure obtained from sp_get_port_by_name().
99 int sp_list_ports(struct sp_port ***list_ptr);
101 Lists the serial ports available on the system. The result obtained is an
102 array of pointers to sp_port structures, terminated by a NULL. The user should
103 allocate a variable of type "struct sp_port **" and pass a pointer to this to
106 The result should be freed after use by calling sp_free_port_list().
108 Returns: SP_OK on success, SP_ERR_FAIL on failure, SP_ERR_MEM on allocation failure,
109 or SP_ERR_ARG if an invalid pointer is passed. If any error is returned,
110 the value pointed to by list_ptr will be set to NULL.
112 void sp_free_port_list(struct sp_port **list);
114 Frees a port list obtained from sp_list_ports().
116 Opening and closing ports
117 -------------------------
119 int sp_open(struct sp_port *port, int flags);
121 Opens the specified serial port.
125 port: Pointer to port structure.
126 flags: Flags to use when opening the serial port. Possible
127 flags are: SP_MODE_RDWR, SP_MODE_RDONLY, and SP_MODE_NONBLOCK.
129 Returns: SP_OK on success, SP_ERR_FAIL on failure, or SP_ERR_ARG
130 if an invalid port is passed.
132 int sp_close(struct sp_port *port);
134 Closes the specified serial port.
136 Returns: SP_OK on success, SP_ERR_FAIL on failure, or SP_ERR_ARG
137 if an invalid port is passed.
139 Setting port parameters
140 -----------------------
142 int sp_set_params(struct sp_port *port, int baudrate,
143 int bits, int parity, int stopbits,
144 int flowcontrol, int rts, int dtr);
146 Sets serial parameters for the specified serial port.
150 port: Pointer to port structure.
151 baudrate: Baud rate to set.
152 bits: Number of data bits to use.
153 parity: Parity setting to use
154 (SP_PARITY_NONE, SP_PARITY_EVEN or SP_PARITY_ODD)
155 stopbits: Number of stop bits to use (1 or 2).
156 flowcontrol: Flow control setting to use
157 (SP_FLOW_NONE, SP_FLOW_HARDWARE or SP_FLOW_SOFTWARE)
159 Returns: SP_OK on success, SP_ERR_FAIL on failure, or SP_ERR_ARG
160 for invalid arguments.
162 Reading, writing and flushing data
163 ----------------------------------
165 int sp_read(struct sp_port *port, const void *buf, size_t count)
167 Reads bytes from the specified serial port. Note that this function may
168 return after reading less than the specified number of bytes; it is the
169 user's responsibility to iterate as necessary in this case.
173 port: Pointer to port structure.
174 buf: Buffer in which to store the bytes read.
175 count: Maximum number of bytes to read.
177 Returns: The number of bytes read, SP_ERR_FAIL on failure,
178 or SP_ERR_ARG for invalid arguments.
180 int sp_write(struct sp_port *port, const void *buf, size_t count)
182 Write bytes to the specified serial port. Note that this function may
183 return after writing less than the specified number of bytes; it is the
184 user's responsibility to iterate as necessary in this case.
188 port: Pointer to port structure.
189 buf: Buffer containing the bytes to write.
190 count: Maximum number of bytes to write.
192 Returns: The number of bytes written, SP_ERR_FAIL on failure,
193 or SP_ERR_ARG for invalid arguments.
195 int sp_flush(struct sp_port *port);
197 Flushes serial port buffers.
199 Returns: SP_OK on success, SP_ERR_FAIL on failure, or SP_ERR_ARG
200 if an invalid port is passed.
205 int sp_last_error_code();
207 Gets the error code for a failed operation.
209 In order to obtain the correct result, this function should be called
210 straight after the failure, before executing any other system operations.
212 Returns: The system's numeric code for the error that caused the last
215 char *sp_last_error_message();
217 Gets the error message for failed operation.
219 In order to obtain the correct result, this function should be called
220 straight after the failure, before executing other system operations.
222 Returns: The system's message for the error that caused the last
223 operation to fail. This string may be allocated by the function,
224 and should be freed after use by calling sp_free_error_message.
226 void sp_free_error_message(char *message);
228 Frees the error message returned by sp_last_error_message().