# Can I send card.attn directly to the notecard?

**URL:** <https://discuss.blues.com/t/can-i-send-card-attn-directly-to-the-notecard/2572>\
**Category:** Notehub.io\
**Created:** [January 5, 2025, 8:31am UTC](https://discuss.blues.com/t/can-i-send-card-attn-directly-to-the-notecard/2572 "2025-01-05T08:31:45Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![tomnorm](https://avatars.discourse-cdn.com/v4/letter/t/e5b9ba/32.png) [@tomnorm](https://discuss.blues.com/u/tomnorm)\
**Post date:** [January 5, 2025, 8:31am UTC](https://discuss.blues.com/t/can-i-send-card-attn-directly-to-the-notecard/2572/1 "2025-01-05T08:31:45Z")

</div>

Hi,  
My MCU sometimes hangs, and I want to restart it using card.attn. Can I send a JSON to Notecard via Notehub, so the MCU will not need to process the JSON?

---

<div class="post-metadata">

**Author:** ![RobLauer](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.blues.com/roblauer/32/1567_2.png) [@RobLauer](https://discuss.blues.com/u/RobLauer)\
**Post date:** [January 6, 2025, 3:59pm UTC](https://discuss.blues.com/t/can-i-send-card-attn-directly-to-the-notecard/2572/2 "2025-01-06T15:59:36Z")

</div>

Hi @tomnorm,

You can use a reserved environment variable to restart a host:

> **[Understanding Environment Variables - Blues Developers](https://dev.blues.io/guides-and-tutorials/notecard-guides/understanding-environment-variables/#reserved-environment-variables)**
>
> Overview of Environment Variables and how to use them

Look up the environment variables that start with `_restart_host`.

Thanks,  
Rob