# Indexed ports

**URL:** <https://forum.sensmetry.com/t/indexed-ports/560>\
**Category:** Bug Reports\
**Tags:** modeler\
**Created:** [August 19, 2026, 2:27pm UTC](https://forum.sensmetry.com/t/indexed-ports/560 "2026-08-19T14:27:32Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![Steven](https://avatars.discourse-cdn.com/v4/letter/s/94ad74/32.png) [@Steven](https://forum.sensmetry.com/u/Steven)\
**Post date:** [August 19, 2026, 2:27pm UTC](https://forum.sensmetry.com/t/indexed-ports/560/1 "2026-08-19T14:27:32Z")

</div>

I am trying to get indexed ports working but seem to be failing.

`ref port GPIO : Interfaces::GPIOPort[32];`

`ref connection TEST1 connect andGate.OUT to soc.GPIO[1];`  
`ref connection TEST2 connect soc.GPIO[2] to andGate.IN1;`

Seems to be a problem with the CLI-Parser?! Trying to use syside viz:  
Unexpected reserved keyword ‘[’, expected one of [“SINGLE\_LINE\_NOTE”, “[”, “$”, “NAME”, “(”, “ElementReference”, “MULTILINE\_NOTE”, “MultiplicityRange”, “OwningMembership”, “ReferenceSubsetting”, “Feature”, “Feature”, “OwningMembership”, “FeatureChaining”, “EndFeatureMembership”, “Feature”].

Any hint what I am doing wrong?

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<div class="post-metadata">

**Author:** ![Simonas](https://yyz2.discourse-cdn.com/flex008/user_avatar/forum.sensmetry.com/simonas/32/13_2.png) [@Simonas](https://forum.sensmetry.com/u/Simonas)\
**Post date:** [August 19, 2026, 2:42pm UTC](https://forum.sensmetry.com/t/indexed-ports/560/2 "2026-08-19T14:42:06Z")

</div>

Hi Steven,

I believe you are mixing up the syntax. `soc.GPIO [1]` would not mean “the first element from GPIO list” like it may do in programming languages. Instead, with this syntax you are trying to set the `soc.GPIO` multiplicity to “1”, which is not supported in this particular `connection` use case.

For referring to an element in a list, you need to use `#(i)` syntax. This is called an _Index expression_ and its description can be found in section 7.4.9.3 of KerML spec.

> _Index expression_. An index expression specifies the invocation of the indexing function `#` from the `BaseFunctions` library model (see 9.4.2). The default behavior for this function is given by the `specializationSequenceFunctions::'#'`, for which the first operand is expected to evaluate to a sequence of values, and the second operand is expected to evaluate to an index into that sequence. Default indexing is from `1` using `Natural` numbers. Note that parentheses are required around the second operand.
> 
> `sensors#(activeSensorIndex)`

However, that is not enough in your case. In your case, you should also modify the model like so (I don’t have the full model, so I am inventing a bit):

```sysml
package StevenForumPost {
    occurrence def Context {
        part andGate {
            port OUT;
            port IN1;
        }

        port def GPIOPort;
        part soc {
            ref port GPIO : GPIOPort [32];
            gpio1 = GPIO#(1); // <- Here I say `gpio1` is my first pin
            gpio2 = GPIO#(2);
        }

        ref connection TEST1 connect andGate.OUT to soc.gpio1; // <- here I connect to that pin
        ref connection TEST2 connect soc.gpio2 to andGate.IN1;
    }
} // package StevenForumPost

```

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<div class="post-metadata">

**Author:** ![Steven](https://avatars.discourse-cdn.com/v4/letter/s/94ad74/32.png) [@Steven](https://forum.sensmetry.com/u/Steven)\
**Post date:** [August 20, 2026, 3:47pm UTC](https://forum.sensmetry.com/t/indexed-ports/560/3 "2026-08-20T15:47:53Z")

</div>

Thank you for the hints, that helps me quite a lot. Sorry for asking basic questions, too.  
This does not work for creating diagrams in CLI, where it is a direct connection between a port of a part and the port of another part, right? It will just create in the diagram a separate connection block showing this connection, but not connecting two parts directly.

---

<div class="post-metadata">

**Author:** ![KestutisJankevicius](https://yyz2.discourse-cdn.com/flex008/user_avatar/forum.sensmetry.com/kestutisjankevicius/32/66_2.png) [@KestutisJankevicius](https://forum.sensmetry.com/u/KestutisJankevicius)\
**Post date:** [August 21, 2026, 5:57am UTC](https://forum.sensmetry.com/t/indexed-ports/560/4 "2026-08-21T05:57:02Z")

</div>

```kotlin
       ref port GPIO : GPIOPort [32];

```

FYI, the “ref” keyword is unnecessary since the port usages are always referential.

Regarding visualization, if you make gpio1/2 usages not just reference usages, but port usages, then Modeler CLI will show it. Also I recommend making port GPIO usage abstract, so that it is clear that in itself these 32 pins are placeholders and need further specialization

```kotlin
        part soc {
            abstract port GPIO : GPIOPort [32];
            port gpio1 = GPIO#(1); 
            port gpio2 = GPIO#(2);
        }

```