MODBUS_NEW_RTU(3) Libmodbus Manual 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
o N for none
o E for even
o 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.
RETURN VALUE
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.
ERRORS
EINVAL
An invalid argument was given.
EXAMPLE
modbus_t *ctx;
ctx = modbus_new_rtu("/dev/ttyUSB0", 115200, 'N', 8, 1);
if (ctx == NULL) {
fprintf(stderr, "Unable to create the libmodbus context
");
return -1;
}
SEE ALSO
modbus_new_tcp(3) modbus_free(3)
AUTHORS
The libmodbus documentation was written by Stephane Raimbault <stephane.raimbault@gmail.com[1]>
NOTES
1. stephane.raimbault@gmail.com
mailto:stephane.raimbault@gmail.com
libmodbus 3.0.3 05/26/2012 MODBUS_NEW_RTU(3)