# Failure on GUI Start Due to Incorrect Search Path for .uavcan Files

**URL:** <https://forum.opencyphal.org/t/failure-on-gui-start-due-to-incorrect-search-path-for-uavcan-files/399>\
**Category:** Applications & Usage\
**Created:** [March 19, 2019, 2:20am UTC](https://forum.opencyphal.org/t/failure-on-gui-start-due-to-incorrect-search-path-for-uavcan-files/399 "2019-03-19T02:20:44Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![davidbitton](https://forum.opencyphal.org/user_avatar/forum.opencyphal.org/davidbitton/32/103_2.png) [@davidbitton](https://forum.opencyphal.org/u/davidbitton)\
**Post date:** [March 19, 2019, 2:20am UTC](https://forum.opencyphal.org/t/failure-on-gui-start-due-to-incorrect-search-path-for-uavcan-files/399/1 "2019-03-19T02:20:44Z")

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I specified a custom .uavcan file when starting the app.

 ![](https://forum.opencyphal.org/uploads/default/original/1X/c25d5f4715b0362970d2e339f49b705a3ecdd4ed.png)

I’m starting off with this

 ![](https://forum.opencyphal.org/uploads/default/original/1X/bdfd427a2b706794d63e8cb4562901e261e2bb21.png)

Line 31 of the [uavcan dsdl file](https://tro.pe/2Ht7tFX) references a type

```auto
uavcan.olliw.uc4h.DistanceSensorProperties[<=1] sensor_property # made an array so that it is optional

```

that is defined in a [file](https://tro.pe/2HzWRp5) alongside that uavcan file in the same folder. Why is the GUI looking elsewhere?

 ![uavcan4hobbyists](https://forum.opencyphal.org/uploads/default/original/1X/2c1cc6d4c4b57871d35a5f0caffaaf365c65b3e0.jpeg)

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**Author:** ![pavel.kirienko](https://forum.opencyphal.org/user_avatar/forum.opencyphal.org/pavel.kirienko/32/9_2.png) [@pavel.kirienko](https://forum.opencyphal.org/u/pavel.kirienko)\
**Post date:** [March 19, 2019, 8:27am UTC](https://forum.opencyphal.org/t/failure-on-gui-start-due-to-incorrect-search-path-for-uavcan-files/399/2 "2019-03-19T08:27:36Z")

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> [@davidbitton](#):
>
> Why is the GUI looking elsewhere?

The GUI is looking where it is supposed to, but the data type `uavcan.olliw.uc4h.DistanceSensorProperties` is not defined.

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**Author:** ![olliw42](https://forum.opencyphal.org/user_avatar/forum.opencyphal.org/olliw42/32/183_2.png) [@olliw42](https://forum.opencyphal.org/u/olliw42)\
**Post date:** [March 19, 2019, 9:44am UTC](https://forum.opencyphal.org/t/failure-on-gui-start-due-to-incorrect-search-path-for-uavcan-files/399/3 "2019-03-19T09:44:21Z")

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> The GUI is looking where it is supposed to

I told him this too 🙂

> the data type `uavcan.olliw.uc4h.DistanceSensorProperties` is not defined

the data type is defined, but he has moved the files&folders to the wrong location, it should be in a uavcan/olliw/ subfolder, as the name uavcan.olliw.xxxx evidences

so, all good, user error 🙂

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**Author:** ![davidbitton](https://forum.opencyphal.org/user_avatar/forum.opencyphal.org/davidbitton/32/103_2.png) [@davidbitton](https://forum.opencyphal.org/u/davidbitton)\
**Post date:** [March 19, 2019, 1:11pm UTC](https://forum.opencyphal.org/t/failure-on-gui-start-due-to-incorrect-search-path-for-uavcan-files/399/4 "2019-03-19T13:11:39Z")

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No, not user error. If the app is going to ask where it can find additional DSDL files, then the app should know to look in the _same_ folder for type defs. I’m not going to own this.

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**Author:** ![davidbitton](https://forum.opencyphal.org/user_avatar/forum.opencyphal.org/davidbitton/32/103_2.png) [@davidbitton](https://forum.opencyphal.org/u/davidbitton)\
**Post date:** [March 19, 2019, 1:13pm UTC](https://forum.opencyphal.org/t/failure-on-gui-start-due-to-incorrect-search-path-for-uavcan-files/399/5 "2019-03-19T13:13:04Z")

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and this is all moot anyway because Mission Planner now has UAVCAN node management and the Cube autopilot can server as an SLCAN.

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**Author:** ![pavel.kirienko](https://forum.opencyphal.org/user_avatar/forum.opencyphal.org/pavel.kirienko/32/9_2.png) [@pavel.kirienko](https://forum.opencyphal.org/u/pavel.kirienko)\
**Post date:** [March 19, 2019, 1:53pm UTC](https://forum.opencyphal.org/t/failure-on-gui-start-due-to-incorrect-search-path-for-uavcan-files/399/6 "2019-03-19T13:53:10Z")

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> [@davidbitton](#):
>
> No, not user error. If the app is going to ask where it can find additional DSDL files, then the app should know to look in the _same_ folder for type defs. I’m not going to own this.

The application behaves correctly according to the specification. It won’t look in the same directory because the included data type is referred to by its absolute name. The core issue here is that OlliW has put his own definitions inside the UAVCAN namespace (`uavcan`), which is expressly prohibited in the spec. The definition is therefore flawed.

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**Author:** ![olliw42](https://forum.opencyphal.org/user_avatar/forum.opencyphal.org/olliw42/32/183_2.png) [@olliw42](https://forum.opencyphal.org/u/olliw42)\
**Post date:** [March 19, 2019, 5:54pm UTC](https://forum.opencyphal.org/t/failure-on-gui-start-due-to-incorrect-search-path-for-uavcan-files/399/7 "2019-03-19T17:54:38Z")

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so we are playing now the blame game  
the issue is that ArduPilot doesn’t allow reasonably meaningful integration of vendor specific dsdls and that the UAVCAN v0 maintainer was irrationally stiff with accepting vendor specif messages, a position the UAVCAN maintainer apparently has concluded himself to not be upholdable and flipped to the other side  
the issue is also that the user has just bluntly copied the files to somewhere without reading the documents as to where the files should go to and without understanding how the UAVCAN dsdl files&folders are organized, and this has absolutely nothing to do with how the vendor specific messages were organized  
we can continue this blame game ad infinitum if you guys want  
TO