modbus_new_rtu - create a libmodbus context for RTU

       The libmodbus documentation was written by Stéphane Raimbault <stephane.raimbault@gmail.com>

libmodbus v3.1.6                                   12/09/2019                                  MODBUS_NEW_RTU(3)

       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
       modbus_set_slave(3) and connect to the serial bus with modbus_connect(3).

EINVAL
           An invalid argument was given.

       ENOMEM
           Out of memory. Possibly, the application hits its memory limit and/or whole system is running out of
           memory.

           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;
           }

       modbus_new_rtu - create a libmodbus context for RTU

       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.

modbus_new_tcp(3) modbus_free(3)

modbus_t*modbus_new_rtu(constchar*device,intbaud,charparity,intdata_bit,intstop_bit);