modbus_read_registers(3) debian man page | unix.com

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)