modbus_new_rtu(3) [debian man page]

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)

Check Out this Related Man Page

MODBUS_READ_REGISTER(3) 					 Libmodbus Manual					   MODBUS_READ_REGISTER(3)

NAME

       modbus_read_registers - read many registers

SYNOPSIS

       int modbus_read_registers(modbus_t *ctx, int addr, int nb, uint16_t *dest);

DESCRIPTION

       The modbus_read_registers() function shall read the content of the nb holding registers to the address addr of the remote device. The
       result of reading is stored in dest array as word values (16 bits).

       You must take care to allocate enough memory to store the results in dest (at least nb * sizeof(uint16_t)).

       The function uses the Modbus function code 0x03 (read holding registers).

RETURN VALUE

       The modbus_read_registers() function shall return the number of read registers if successful. Otherwise it shall return -1 and set errno.

ERRORS

       EMBMDATA
	   Too many registers requested

EXAMPLE

	   modbus_t *ctx;
	   uint16_t tab_reg[64];
	   int rc;
	   int i;

	   ctx = modbus_new_tcp("127.0.0.1", 1502);
	   if (modbus_connect(ctx) == -1) {
	       fprintf(stderr, "Connection failed: %s
", modbus_strerror(errno));
	       modbus_free(ctx);
	       return -1;
	   }

	   rc = modbus_read_registers(ctx, 0, 10, tab_reg);
	   if (rc == -1) {
	       fprintf(stderr, "%s
", modbus_strerror(errno));
	       return -1;
	   }

	   for (i=0; i < rc; i++) {
	       printf("reg[%d]=%d (0x%X)
", i, tab_reg[i], tab_reg[i]);
	   }

	   modbus_close(ctx);
	   modbus_free(ctx);

SEE ALSO

       modbus_write_register(3) modbus_write_registers(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_READ_REGISTER(3)

Linux and UNIX Man Pages

modbus_new_rtu(3) [debian man page]

Check Out this Related Man Page