modbus_new_rtu(3) ================= NAME ---- modbus_new_rtu - create a libmodbus context for RTU SYNOPSIS -------- *modbus_t *modbus_new_rtu(const char *'device', int 'baud', char 'parity', int 'data_bit', int 'stop_bit');* DESCRIPTION ----------- The *modbus_new_rtu()* function shall allocate and initialize a _modbus_t_ structure to communicate in RTU mode on a serial line. The _device_ argument specifies the name of the serial port handled by the OS, eg. "/dev/ttyS0" or "/dev/ttyUSB0". On Windows, it's necessary to prepend COM name with "\\.\" for COM number greater than 9, eg. "\\\\.\\COM10". See http://msdn.microsoft.com/en-us/library/aa365247(v=vs.85).aspx for details The _baud_ argument specifies the baud rate of the communication, eg. 9600, 19200, 57600, 115200, etc. The _parity_ argument can have one of the following values::: * _N_ for none * _E_ for even * _O_ for odd The _data_bits_ argument specifies the number of bits of data, the allowed values are 5, 6, 7 and 8. The _stop_bits_ argument specifies the bits of stop, the allowed values are 1 and 2. Once the _modbus_t_ structure is initialized, you must set the slave of your device with linkmb:modbus_set_slave[3] and connect to the serial bus with linkmb:modbus_connect[3]. RETURN VALUE ------------ The function shall return a pointer to a _modbus_t_ structure if successful. Otherwise it shall return NULL and set errno to one of the values defined below. ERRORS ------ *EINVAL*:: An invalid argument was given. EXAMPLE ------- [source,c] ------------------- modbus_t *ctx; ctx = modbus_new_rtu("/dev/ttyUSB0", 115200, 'N', 8, 1); if (ctx == NULL) { fprintf(stderr, "Unable to create the libmodbus context\n"); return -1; } modbus_set_slave(ctx, YOUR_DEVICE_ID); if (modbus_connect(ctx) == -1) { fprintf(stderr, "Connection failed: %s\n", modbus_strerror(errno)); modbus_free(ctx); return -1; } ------------------- SEE ALSO -------- linkmb:modbus_new_tcp[3] linkmb:modbus_free[3] AUTHORS ------- The libmodbus documentation was written by Stéphane Raimbault