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\n", modbus_strerror(errno));
               modbus_free(ctx);
               return -1;
           }

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

           for (i=0; i < rc; i++) {
               printf("reg[%d]=%d (0x%X)\n", 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 Stéphane Raimbault
       <stephane.raimbault@gmail.com[1]>

NOTES

        1. stephane.raimbault@gmail.com
           mailto:stephane.raimbault@gmail.com