Reading REFERENCE TO <TYPE> and dereferenced pointer always returns invalid index group

Hi,

The Scada server I use (SpiderControl) uses the ADS-sum command to reach the variables inside my PLC. Everything is alright for most of the variables.

My only concern is for REFERENCE TO and REFERENCE TO ARRAY variables. I often use those one for my recipe or to simplify the call inside my Scada server. The problem is that REFERENCE TO is not supported by the ADS-sum command and lead always to an invalid index group error.

I try to replicate this behavior using the pyads library. I use the read_list_by_name method and the same behavior occurs.

here is the code in the PLC:

PROGRAM MAIN
VAR
    var_int    : INT              := 10;
    ref_to_int : REFERENCE TO INT REF= Var_int;
    ptr_to_int : POINTER TO INT := ADR(var_int);

    arr_var_int    : ARRAY[0..4] OF INT               := [10, 11, 12, 13, 14];
    ref_to_arr_int : REFERENCE TO ARRAY[0..4] OF INT  REF= arr_var_int;
END_VAR

here the code on pyads:

import pyads

plc = pyads.Connection('127.0.0.1.1.1', pyads.PORT_TC3PLC1)
plc.open()

var_list_test = var_list_test = [
'MAIN.var_int',
'MAIN.ref_to_int',
'MAIN.ptr_to_int^',
'MAIN.arr_var_int[0]',
'MAIN.ref_to_arr_int[0]']

print(plc.read_list_by_name(var_list_test))

And it returns this:

{'MAIN.var_int': 10, 'MAIN.ref_to_int': 'invalid index group', 'MAIN.ptr_to_int^': 'invalid index group', 'MAIN.arr_var_int[0]': 10, 'MAIN.ref_to_arr_int[0]': 'invalid index group'}

Is there a list of unsuported type for this command? This page doesn't inform us about type limitation: https://infosys.beckhoff.com/english.php?content=../content/1033/tcsample_vc/html/tcadsdll_api_cpp_sample17.htm&id=

Beckhoff / ADS

Reading REFERENCE TO <TYPE> and dereferenced pointer always returns invalid index group #158