# Heartbeat 1 and Heartbeat 2

Heartbeats 1 and 2 were created to let you know that the device is alive periodically. We have also added additional settings and the possibility to append various data. Each heartbeat is controlled by 3 registers - a total of *6 registers* (**from 0x07 to 0x0C**).

**Heartbeat period** is controlled by registers 0x07 and 0x0A for Heartbeats 1 and 2 respectively. The values of these registers are encoded as a *SimpleTime* value in a single byte.

*Example: Setting the Heartbeat 1 period register (0x07) to 10 minutes (0x4A) would make the device send the heartbeat message every 10 minutes (duh!:)).*

***

**Heartbeat settings** registers (**0x08** and **0x0B** for **Heartbeats 1** and **2** respectively) control behavior of the heartbeat event. The 8 binary flags (bits) of this **one byte value** modify the following:

| **Bit** | **Set to 0**                                                                                       | **Set to 1**                                                                                        |
| ------- | -------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------- |
| **7**   | <p>Heartbeat time period is <strong>not</strong> reset<br>by other events sent from the device</p> | <p>Heartbeat time period is reset by other events<br>sent from the device (to save the battery)</p> |
| **6**   | Heartbeats sent while armed only                                                                   | Heartbeats sent regardless of device state                                                          |
| **5**   | Uplink only heartbeat message                                                                      | Heartbeat message requests standard downlink                                                        |
| **4**   | Uplink only heartbeat message                                                                      | <p>Heartbeat message requests downlink<br>with world time to sync the internal clock</p>            |
| **3**   | Standard 3 frames transmitted                                                                      | Only one frame message will be sent                                                                 |
| **2**   | (empty)                                                                                            | (empty)                                                                                             |
| **1**   | (empty)                                                                                            | (empty)                                                                                             |
| **0**   | (empty)                                                                                            | (empty)                                                                                             |

*Example: Setting the Heartbeat 1 settings register (0x08) to value 0x40 (01000000) would make the device send the heartbeat message even when disarmed.*

**Heartbeat appended payload mask** registers (**0x09** and **0x0C** for **Heartbeats 1** and **2** respectively) control the various data that can be appended to the heartbeat message. The mask is identical to the standard *Appended payload* mask that controls what data is sent with events from 0x00 to 0x7F.

*Example: The default value of these registers is 0xC0 (11000000) - this means that with every heartbeat, battery voltage and temperature will be appended.*

{% content-ref url="/pages/11eIe9gH2cR6tZOnJmho" %}
[Appended payload](/kb/simple-api-6-generation/modes/api-6-mode-independent-information-and-events_15237121/appended-payload.md)
{% endcontent-ref %}


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