# Problem at canardTxPush()

**URL:** <https://forum.opencyphal.org/t/problem-at-canardtxpush/965>\
**Category:** Libcanard\
**Created:** [October 20, 2020, 5:24pm UTC](https://forum.opencyphal.org/t/problem-at-canardtxpush/965 "2020-10-20T17:24:15Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![hugo](https://forum.opencyphal.org/letter_avatar_proxy/v4/letter/h/b38774/32.png) [@hugo](https://forum.opencyphal.org/u/hugo)\
**Post date:** [October 20, 2020, 5:24pm UTC](https://forum.opencyphal.org/t/problem-at-canardtxpush/965/1 "2020-10-20T17:24:15Z")

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Hi

Somehow I had this working on an Arduino Mega at some time but I “tried to fix what was not broken” and now it is not working anymore and I don’t know what is wrong. I know canardTxPush() is returning -2 but i don’t know why. Anybody can help with some insight please?

The code is here:  
[https://github.com/hugo-a-garcia/avr-can-sender](https://github.com/hugo-a-garcia/avr-can-sender)

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<div class="post-metadata">

**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:** [October 20, 2020, 5:44pm UTC](https://forum.opencyphal.org/t/problem-at-canardtxpush/965/2 "2020-10-20T17:44:54Z")

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The relevant case is this one:

> <https://github.com/OpenCyphal/libcanard/blob/54a004bd59c2a637c7b39e3ea2feac7142f74489/libcanard/canard.h#L392>

The maximum subject-ID value is 8191 (changed in UAVCAN Spec v1.0-beta, used to be 32767):

> <https://github.com/OpenCyphal/libcanard/blob/54a004bd59c2a637c7b39e3ea2feac7142f74489/libcanard/canard.h#L133>

This change is described in the changelog here:

> **[Release v1.0-beta · OpenCyphal/specification](https://github.com/OpenCyphal/specification/releases/tag/v1.0-beta)**
>
> Compared to v1.0-alpha, the differences are as follows (the motivation is provided on the forum):
> 
> 
> The physical layer specification has been removed. It is now up to the domain-specific UAVCAN-bas...

You need to update your subject-ID constants.