diff --git a/README b/README index e69de29..5958d89 100644 --- a/README +++ b/README @@ -0,0 +1,204 @@ +---------------------------------------------------------------- +libserialport: cross-platform library for accessing serial ports +---------------------------------------------------------------- + +libserialport is a minimal library written in C that is intended to take care +of the OS-specific details when writing software that uses serial ports. + +By writing your serial code to use libserialport, you enable it to work +transparently on any platform supported by the library. + +The operations that are supported are: + +- Port enumeration (obtaining a list of serial ports on the system). +- Opening and closing ports. +- Setting port parameters (baud rate, parity, etc). +- Reading, writing and flushing data. +- Obtaining error information. + +libserialport is an open source project released under the LGPL3+ license. + +Status +====== + +The library should build and work on any Windows or Unix-based system. If it +does not, please submit a bug. + +Enumeration is currently only implemented on Windows, Mac OS X and Linux. On +other systems enumeration will return no results, but ports can still be opened +by name and then used. + +If you know how to enumerate available ports on another OS, please submit a bug +with this information, or better still a patch implementing it. + +Future +====== + +Future versions will add additional API calls for obtaining metadata about a +port, e.g. for USB devices the USB VID and PID of the underlying device. + +Dependencies +============ + +On Linux, libudev is required. On other systems no other libraries are required. + +The libudev dependency could be eliminated in favour of direct sysfs queries at +the cost of some brevity. This is not currently a priority but if you feel like +doing this feel free to submit a patch. + +Building +======== + +The package uses a GNU style build system and requires a Unix style shell. +On Windows it can be built with the MinGW toolchain and MSYS environment. + +Run "./autogen.sh" to generate the build system, "./configure" to setup, then +"make" to build the library and "make install" to install it. + +API +=== + +The API is simple, and designed to be a minimal wrapper around the serial port +support in each OS. + +Most functions take a pointer to a struct sp_port, which represents an open +port. This structure should be allocated by the user and is populated by +sp_open(). It can be freed safely after sp_close(). + +All functions can return only two possible error values. SP_ERR_ARG indicates +the function was called with invalid arguments. SP_ERR_FAIL indicates that the +OS reported a failure. Both these error values are negative. + +When SP_ERR_FAIL is returned, an error code or string description of the error +can be obtained by calling sp_last_error_code() or sp_last_error_message(). The +error code or message is that provided by the OS; libserialport does not define +any error codes or messages of its own. + +Functions calls that succeed return SP_OK, which is equal to zero, or where +otherwise documented a positive value. + +The available functions are as follows: + +Enumeration +----------- + +char **sp_list_ports(); + + Lists the serial ports available on the system. The value returned is an array + of port names as C strings, terminated by a NULL. It should be freed after use + by calling sp_free_port_list(). + +void sp_free_port_list(char **list); + + Frees the data structure returned by sp_list_ports(). + +Opening and closing ports +------------------------- + +int sp_open(struct sp_port *port, char *portname, int flags); + + Opens the specified serial port. + + Parameters: + + port: Pointer to empty port structure, allocated by caller. + portname: Name of port to open. + flags: Flags to use when opening the serial port. Possible + flags are: SP_MODE_RDWR, SP_MODE_RDONLY, and SP_MODE_NONBLOCK. + + Returns: SP_OK on success, SP_ERR_FAIL on failure, or SP_ERR_ARG + if an invalid port or name is passed. + +int sp_close(struct sp_port *port); + + Closes the specified serial port. + + Returns: SP_OK on success, SP_ERR_FAIL on failure, or SP_ERR_ARG + if an invalid port is passed. + +Setting port parameters +----------------------- + +int sp_set_params(struct sp_port *port, int baudrate, + int bits, int parity, int stopbits, + int flowcontrol, int rts, int dtr); + + Sets serial parameters for the specified serial port. + + Parameters: + + port: Pointer to port structure. + baudrate: Baud rate to set. + bits: Number of data bits to use. + parity: Parity setting to use + (SP_PARITY_NONE, SP_PARITY_EVEN or SP_PARITY_ODD) + stopbits: Number of stop bits to use (1 or 2). + flowcontrol: Flow control setting to use + (SP_FLOW_NONE, SP_FLOW_HARDWARE or SP_FLOW_SOFTWARE) + + Returns: SP_OK on success, SP_ERR_FAIL on failure, or SP_ERR_ARG + for invalid arguments. + +Reading, writing and flushing data +---------------------------------- + +int sp_read(struct sp_port *port, const void *buf, size_t count) + + Reads a number of bytes from the specified serial port. + + Parameters: + + port: Pointer to port structure. + buf: Buffer in which to store the bytes read. + count: Number of bytes to read. + + Returns: The number of bytes read, SP_ERR_FAIL on failure, + or SP_ERR_ARG for invalid arguments. + +int sp_write(struct sp_port *port, const void *buf, size_t count) + + Writes a number of bytes to the specified serial port. + + Parameters: + + port: Pointer to port structure. + buf: Buffer containing the bytes to write. + count: Number of bytes to write. + + Returns: The number of bytes written, SP_ERR_FAIL on failure, + or SP_ERR_ARG for invalid arguments. + +int sp_flush(struct sp_port *port); + + Flushes serial port buffers. + + Returns: SP_OK on success, SP_ERR_FAIL on failure, or SP_ERR_ARG + if an invalid port is passed. + +Error handling +-------------- + +int sp_last_error_code(); + + Gets the error code for a failed operation. + + In order to obtain the correct result, this function should be called + straight after the failure, before executing any other system operations. + + Returns: The system's numeric code for the error that caused the last + operation to fail. + +char *sp_last_error_message(); + + Gets the error message for failed operation. + + In order to obtain the correct result, this function should be called + straight after the failure, before executing other system operations. + + Returns: The system's message for the error that caused the last + operation to fail. This string may be allocated by the function, + and should be freed after use by calling sp_free_error_message. + +void sp_free_error_message(char *message); + + Frees the error message returned by sp_last_error_message().