Create a libmodbus context for rtu
modbus_t *modbus_new_rtu(const char *device, int baud, char parity, int data_bit, int stop_bit);
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\(cqs necessary to prepend COM name with \\.\ for COM number greater than 9, eg. \\\\.\\COM10. See \m[blue]http://msdn.microsoft.com/en-us/library/aa365247(v=vs.85).aspx\m[] 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.
The modbus_new_rtu() 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.
EINVAL
An invalid argument was given.
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;
}
The libmodbus documentation was written by St\('ephane Raimbault <\m[blue][email protected]\m[]\s-2\u[1]\d\s+2>
mailto:[email protected]