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1 | ---------------------------------------------------------------- | |
2 | libserialport: cross-platform library for accessing serial ports | |
3 | ---------------------------------------------------------------- | |
4 | ||
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. | |
7 | ||
8 | By writing your serial code to use libserialport, you enable it to work | |
9 | transparently on any platform supported by the library. | |
10 | ||
11 | The operations that are supported are: | |
12 | ||
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. | |
18 | ||
19 | libserialport is an open source project released under the LGPL3+ license. | |
20 | ||
21 | Status | |
22 | ====== | |
23 | ||
24 | The library should build and work on any Windows or Unix-based system. If it | |
25 | does not, please submit a bug. | |
26 | ||
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. | |
30 | ||
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. | |
33 | ||
34 | Future | |
35 | ====== | |
36 | ||
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. | |
39 | ||
40 | Dependencies | |
41 | ============ | |
42 | ||
43 | On Linux, libudev is required. On other systems no other libraries are required. | |
44 | ||
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. | |
48 | ||
49 | Building | |
50 | ======== | |
51 | ||
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. | |
54 | ||
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. | |
57 | ||
58 | API | |
59 | === | |
60 | ||
61 | The API is simple, and designed to be a minimal wrapper around the serial port | |
62 | support in each OS. | |
63 | ||
64 | Most functions take a pointer to a struct sp_port, which represents a serial | |
65 | port. These structures are always allocated and freed by the library, using the | |
66 | functions in the 'Enumeration' section below. | |
67 | ||
68 | All functions can return only three possible error values. SP_ERR_ARG indicates | |
69 | the function was called with invalid arguments. SP_ERR_FAIL indicates that the | |
70 | OS reported a failure. SP_ERR_MEM indicates that a memory allocation failed. | |
71 | All of these error values are negative. | |
72 | ||
73 | When SP_ERR_FAIL is returned, an error code or string description of the error | |
74 | can be obtained by calling sp_last_error_code() or sp_last_error_message(). The | |
75 | error code or message is that provided by the OS; libserialport does not define | |
76 | any error codes or messages of its own. | |
77 | ||
78 | Functions calls that succeed return SP_OK, which is equal to zero, or where | |
79 | otherwise documented a positive value. | |
80 | ||
81 | The available functions are as follows: | |
82 | ||
83 | Enumeration | |
84 | ----------- | |
85 | ||
86 | int sp_get_port_by_name(const char *portname, struct sp_port **port_ptr); | |
87 | ||
88 | Obtains a pointer to a new sp_port structure representing the named port. The | |
89 | user should allocate a variable of type "struct sp_port *" and pass a pointer | |
90 | to this to receive the result. | |
91 | ||
92 | The result should be freed after use by calling sp_free_port(). | |
93 | ||
94 | Returns: SP_OK on success, SP_ERR_FAIL on failure, SP_ERR_MEM on allocation | |
95 | failure, or SP_ERR_ARG if an invalid pointer is passed. If any error | |
96 | is returned, the variable pointed to by port_ptr will be set to NULL. | |
97 | Otherwise, it will be set to point to the newly allocated port. | |
98 | ||
99 | void sp_free_port(struct sp_port *port); | |
100 | ||
101 | Frees a port structure obtained from sp_get_port_by_name(). | |
102 | ||
103 | int sp_list_ports(struct sp_port ***list_ptr); | |
104 | ||
105 | Lists the serial ports available on the system. The result obtained is an | |
106 | array of pointers to sp_port structures, terminated by a NULL. The user should | |
107 | allocate a variable of type "struct sp_port **" and pass a pointer to this to | |
108 | receive the result. | |
109 | ||
110 | The result should be freed after use by calling sp_free_port_list(). | |
111 | ||
112 | Returns: SP_OK on success, SP_ERR_FAIL on failure, SP_ERR_MEM on allocation | |
113 | failure, or SP_ERR_ARG if an invalid pointer is passed. If any error | |
114 | is returned, the variable pointed to by list_ptr will be set to NULL. | |
115 | Otherwise, it will be set to point to the newly allocated array. | |
116 | ||
117 | void sp_free_port_list(struct sp_port **list); | |
118 | ||
119 | Frees a port list obtained from sp_list_ports(). | |
120 | ||
121 | Opening and closing ports | |
122 | ------------------------- | |
123 | ||
124 | int sp_open(struct sp_port *port, int flags); | |
125 | ||
126 | Opens the specified serial port. | |
127 | ||
128 | Parameters: | |
129 | ||
130 | port: Pointer to port structure. | |
131 | flags: Flags to use when opening the serial port. Possible | |
132 | flags are: SP_MODE_RDWR, SP_MODE_RDONLY, and SP_MODE_NONBLOCK. | |
133 | ||
134 | Returns: SP_OK on success, SP_ERR_FAIL on failure, SP_ERR_MEM on allocation | |
135 | failure, or SP_ERR_ARG if an invalid port is passed. | |
136 | ||
137 | int sp_close(struct sp_port *port); | |
138 | ||
139 | Closes the specified serial port. | |
140 | ||
141 | Returns: SP_OK on success, SP_ERR_FAIL on failure, or SP_ERR_ARG | |
142 | if an invalid port is passed. | |
143 | ||
144 | Setting port parameters | |
145 | ----------------------- | |
146 | ||
147 | int sp_set_params(struct sp_port *port, int baudrate, | |
148 | int bits, int parity, int stopbits, | |
149 | int flowcontrol, int rts, int dtr); | |
150 | ||
151 | Sets serial parameters for the specified serial port. | |
152 | ||
153 | Parameters: | |
154 | ||
155 | port: Pointer to port structure. | |
156 | baudrate: Baud rate to set. | |
157 | bits: Number of data bits to use. | |
158 | parity: Parity setting to use | |
159 | (SP_PARITY_NONE, SP_PARITY_EVEN or SP_PARITY_ODD) | |
160 | stopbits: Number of stop bits to use (1 or 2). | |
161 | flowcontrol: Flow control setting to use | |
162 | (SP_FLOW_NONE, SP_FLOW_HARDWARE or SP_FLOW_SOFTWARE) | |
163 | ||
164 | Returns: SP_OK on success, SP_ERR_FAIL on failure, or SP_ERR_ARG | |
165 | for invalid arguments. | |
166 | ||
167 | Reading, writing and flushing data | |
168 | ---------------------------------- | |
169 | ||
170 | int sp_read(struct sp_port *port, const void *buf, size_t count) | |
171 | ||
172 | Reads bytes from the specified serial port. Note that this function may | |
173 | return after reading less than the specified number of bytes; it is the | |
174 | user's responsibility to iterate as necessary in this case. | |
175 | ||
176 | Parameters: | |
177 | ||
178 | port: Pointer to port structure. | |
179 | buf: Buffer in which to store the bytes read. | |
180 | count: Maximum number of bytes to read. | |
181 | ||
182 | Returns: The number of bytes read, SP_ERR_FAIL on failure, | |
183 | or SP_ERR_ARG for invalid arguments. | |
184 | ||
185 | int sp_write(struct sp_port *port, const void *buf, size_t count) | |
186 | ||
187 | Write bytes to the specified serial port. Note that this function may | |
188 | return after writing less than the specified number of bytes; it is the | |
189 | user's responsibility to iterate as necessary in this case. | |
190 | ||
191 | Parameters: | |
192 | ||
193 | port: Pointer to port structure. | |
194 | buf: Buffer containing the bytes to write. | |
195 | count: Maximum number of bytes to write. | |
196 | ||
197 | Returns: The number of bytes written, SP_ERR_FAIL on failure, | |
198 | or SP_ERR_ARG for invalid arguments. | |
199 | ||
200 | int sp_flush(struct sp_port *port); | |
201 | ||
202 | Flushes serial port buffers. | |
203 | ||
204 | Returns: SP_OK on success, SP_ERR_FAIL on failure, or SP_ERR_ARG | |
205 | if an invalid port is passed. | |
206 | ||
207 | Error handling | |
208 | -------------- | |
209 | ||
210 | int sp_last_error_code(); | |
211 | ||
212 | Gets the error code for a failed operation. | |
213 | ||
214 | In order to obtain the correct result, this function should be called | |
215 | straight after the failure, before executing any other system operations. | |
216 | ||
217 | Returns: The system's numeric code for the error that caused the last | |
218 | operation to fail. | |
219 | ||
220 | char *sp_last_error_message(); | |
221 | ||
222 | Gets the error message for failed operation. | |
223 | ||
224 | In order to obtain the correct result, this function should be called | |
225 | straight after the failure, before executing other system operations. | |
226 | ||
227 | Returns: The system's message for the error that caused the last | |
228 | operation to fail. This string may be allocated by the function, | |
229 | and should be freed after use by calling sp_free_error_message. | |
230 | ||
231 | void sp_free_error_message(char *message); | |
232 | ||
233 | Frees the error message returned by sp_last_error_message(). |