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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 | ||
d54e9004 ML |
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(). | |
0a16d4de | 66 | |
e9a2f9c9 | 67 | All functions can return only three possible error values. SP_ERR_ARG indicates |
0a16d4de | 68 | the function was called with invalid arguments. SP_ERR_FAIL indicates that the |
e9a2f9c9 | 69 | OS reported a failure. SP_ERR_MEM indicates that a memory allocation failed. |
01619328 | 70 | All of these error values are negative. |
0a16d4de ML |
71 | |
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. | |
76 | ||
77 | Functions calls that succeed return SP_OK, which is equal to zero, or where | |
78 | otherwise documented a positive value. | |
79 | ||
80 | The available functions are as follows: | |
81 | ||
82 | Enumeration | |
83 | ----------- | |
84 | ||
01619328 | 85 | int sp_get_port_by_name(const char *portname, struct sp_port **port_ptr); |
0a16d4de | 86 | |
01619328 ML |
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. | |
b9a462bb ML |
90 | |
91 | The result should be freed after use by calling sp_free_port(). | |
01619328 | 92 | |
b9a462bb ML |
93 | Returns: SP_OK on success, SP_ERR_FAIL on failure, SP_ERR_MEM on allocation |
94 | failure, or SP_ERR_ARG if an invalid pointer is passed. If any error | |
95 | is returned, the variable pointed to by port_ptr will be set to NULL. | |
96 | Otherwise, it will be set to point to the newly allocated port. | |
01619328 ML |
97 | |
98 | void sp_free_port(struct sp_port *port); | |
99 | ||
100 | Frees a port structure obtained from sp_get_port_by_name(). | |
101 | ||
102 | int sp_list_ports(struct sp_port ***list_ptr); | |
103 | ||
104 | Lists the serial ports available on the system. The result obtained is an | |
105 | array of pointers to sp_port structures, terminated by a NULL. The user should | |
106 | allocate a variable of type "struct sp_port **" and pass a pointer to this to | |
107 | receive the result. | |
108 | ||
109 | The result should be freed after use by calling sp_free_port_list(). | |
110 | ||
b9a462bb ML |
111 | Returns: SP_OK on success, SP_ERR_FAIL on failure, SP_ERR_MEM on allocation |
112 | failure, or SP_ERR_ARG if an invalid pointer is passed. If any error | |
113 | is returned, the variable pointed to by list_ptr will be set to NULL. | |
114 | Otherwise, it will be set to point to the newly allocated array. | |
0a16d4de | 115 | |
d54e9004 | 116 | void sp_free_port_list(struct sp_port **list); |
0a16d4de | 117 | |
01619328 | 118 | Frees a port list obtained from sp_list_ports(). |
0a16d4de ML |
119 | |
120 | Opening and closing ports | |
121 | ------------------------- | |
122 | ||
d54e9004 | 123 | int sp_open(struct sp_port *port, int flags); |
0a16d4de ML |
124 | |
125 | Opens the specified serial port. | |
126 | ||
127 | Parameters: | |
128 | ||
d54e9004 | 129 | port: Pointer to port structure. |
0a16d4de ML |
130 | flags: Flags to use when opening the serial port. Possible |
131 | flags are: SP_MODE_RDWR, SP_MODE_RDONLY, and SP_MODE_NONBLOCK. | |
132 | ||
133 | Returns: SP_OK on success, SP_ERR_FAIL on failure, or SP_ERR_ARG | |
01619328 | 134 | if an invalid port is passed. |
0a16d4de ML |
135 | |
136 | int sp_close(struct sp_port *port); | |
137 | ||
138 | Closes the specified serial port. | |
139 | ||
140 | Returns: SP_OK on success, SP_ERR_FAIL on failure, or SP_ERR_ARG | |
141 | if an invalid port is passed. | |
142 | ||
143 | Setting port parameters | |
144 | ----------------------- | |
145 | ||
146 | int sp_set_params(struct sp_port *port, int baudrate, | |
147 | int bits, int parity, int stopbits, | |
148 | int flowcontrol, int rts, int dtr); | |
149 | ||
150 | Sets serial parameters for the specified serial port. | |
151 | ||
152 | Parameters: | |
153 | ||
154 | port: Pointer to port structure. | |
155 | baudrate: Baud rate to set. | |
156 | bits: Number of data bits to use. | |
157 | parity: Parity setting to use | |
158 | (SP_PARITY_NONE, SP_PARITY_EVEN or SP_PARITY_ODD) | |
159 | stopbits: Number of stop bits to use (1 or 2). | |
160 | flowcontrol: Flow control setting to use | |
161 | (SP_FLOW_NONE, SP_FLOW_HARDWARE or SP_FLOW_SOFTWARE) | |
162 | ||
163 | Returns: SP_OK on success, SP_ERR_FAIL on failure, or SP_ERR_ARG | |
164 | for invalid arguments. | |
165 | ||
166 | Reading, writing and flushing data | |
167 | ---------------------------------- | |
168 | ||
169 | int sp_read(struct sp_port *port, const void *buf, size_t count) | |
170 | ||
25ab82f6 ML |
171 | Reads bytes from the specified serial port. Note that this function may |
172 | return after reading less than the specified number of bytes; it is the | |
173 | user's responsibility to iterate as necessary in this case. | |
0a16d4de ML |
174 | |
175 | Parameters: | |
176 | ||
177 | port: Pointer to port structure. | |
178 | buf: Buffer in which to store the bytes read. | |
25ab82f6 | 179 | count: Maximum number of bytes to read. |
0a16d4de ML |
180 | |
181 | Returns: The number of bytes read, SP_ERR_FAIL on failure, | |
182 | or SP_ERR_ARG for invalid arguments. | |
183 | ||
184 | int sp_write(struct sp_port *port, const void *buf, size_t count) | |
185 | ||
25ab82f6 ML |
186 | Write bytes to the specified serial port. Note that this function may |
187 | return after writing less than the specified number of bytes; it is the | |
188 | user's responsibility to iterate as necessary in this case. | |
0a16d4de ML |
189 | |
190 | Parameters: | |
191 | ||
192 | port: Pointer to port structure. | |
193 | buf: Buffer containing the bytes to write. | |
25ab82f6 | 194 | count: Maximum number of bytes to write. |
0a16d4de ML |
195 | |
196 | Returns: The number of bytes written, SP_ERR_FAIL on failure, | |
197 | or SP_ERR_ARG for invalid arguments. | |
198 | ||
199 | int sp_flush(struct sp_port *port); | |
200 | ||
201 | Flushes serial port buffers. | |
202 | ||
203 | Returns: SP_OK on success, SP_ERR_FAIL on failure, or SP_ERR_ARG | |
204 | if an invalid port is passed. | |
205 | ||
206 | Error handling | |
207 | -------------- | |
208 | ||
209 | int sp_last_error_code(); | |
210 | ||
211 | Gets the error code for a failed operation. | |
212 | ||
213 | In order to obtain the correct result, this function should be called | |
214 | straight after the failure, before executing any other system operations. | |
215 | ||
216 | Returns: The system's numeric code for the error that caused the last | |
217 | operation to fail. | |
218 | ||
219 | char *sp_last_error_message(); | |
220 | ||
221 | Gets the error message for failed operation. | |
222 | ||
223 | In order to obtain the correct result, this function should be called | |
224 | straight after the failure, before executing other system operations. | |
225 | ||
226 | Returns: The system's message for the error that caused the last | |
227 | operation to fail. This string may be allocated by the function, | |
228 | and should be freed after use by calling sp_free_error_message. | |
229 | ||
230 | void sp_free_error_message(char *message); | |
231 | ||
232 | Frees the error message returned by sp_last_error_message(). |