# Hex Payload Decoder

### Overview

The **Hex Payload Decoder** allows you to **convert incoming hex string payloads into valid JSON data** for non-LoRaWAN data sources.

{% hint style="info" %}
The **Hex Payload Decoder** is only applicable for **non-LoRaWAN data sources**, such as [MQTT](/data-sources/mqtt.md), [HTTP](/data-sources/http.md), or [Onomondo](/data-sources/no-code-integrations/onomondo.md). LoRaWAN devices use [**Device Templates**](/platform/functions/decoder-function/lorawan-device-template-decoder.md) or [**Custom Decoder**](/platform/functions/decoder-function/lorawan-custom-decoder.md) for decoding.
{% endhint %}

### How It Works

{% @mermaid/diagram content="graph LR;
A\[Non-LoRaWAN Device Sends Hex Data] --> B{Decoder Function Available?};

B -- No --> C\[Data Cannot Be Processed];
B -- Yes --> F\[Convert Hex to JSON];

F --> G\[Store Decoded Data in Qubitro];

%% Style Adjustments
style A fill:#d9d9d9,stroke:#000,color:#000;
style B fill:#f2f2f2,stroke:#000,color:#000;
style C fill:#f2f2f2,stroke:#000,color:#000;
style F fill:#CBC3E3,stroke:#000,color:#000;  %% Purple from previous diagrams
style G fill:#CBC3E3,stroke:#000,color:#000;  %% Purple from previous diagrams" %}

{% hint style="warning" %}
If a [Transformation Function](https://qubitro.gitbook.io/qubitro-documentation/platform/functions/transformation-function) is enabled, data will be processed before storage. The decoder applies first, and then any defined transformation function modifies the data before it is stored in Qubitro.
{% endhint %}

### Tips

* **Avoid** unnecessary logic or external dependencies that could slow down execution.
* **Use** arithmetic operations and bit shifts to convert hex values into readable fields.
* Keep payload formatters **simple** and lightweight.

{% hint style="success" %}
Need help reviewing your custom formatter? Our team can assist in checking your code for compatibility. Reach out via the [Support Page](https://qubitro.gitbook.io/qubitro-documentation/help-center).
{% endhint %}

### Required Input Format

Data must be published as JSON with the following structure:

```json
{ "payload_hex": "hex_value" }
```

{% hint style="warning" %}
**The key must be `"payload_hex"`** in the incoming JSON payload. Any other key name will not be recognized by the system.
{% endhint %}

### Function Schema

A decoder function processes **incoming hex payloads** and returns a structured JSON object.

#### Function Parameters

The decoder function receives a **single parameter: `input`**, which contains:

* **bytes** → A byte array representing the raw payload received.

```javascript
function decoder(input) {
  // Your decoding logic here
}
```

#### Return Values

{% hint style="warning" %}
To ensure compatibility with Qubitro’s no-code suite, the output should be a key-value JSON object.
{% endhint %}

### Example

{% stepper %}
{% step %}
**Incoming payload**

```json
{ "payload_hex": "7B2274656D7065726174757265223A32352C2268756D6964697479223A36302C227072657373757265223A313031332C2262617474657279223A39307D" }
```

{% endstep %}

{% step %}
**Formatter code**

```javascript
function decoder(input) {
    
    // Extract values from the input bytes array

    // First byte represents temperature
    let temperature = input.bytes[0];  

    // Second byte represents humidity
    let humidity = input.bytes[1];     

    // Third & Fourth bytes represent pressure (16-bit value)
    let pressure = (input.bytes[2] << 8) | input.bytes[3]; 

    // Fifth byte represents battery level
    let battery = input.bytes[4];      

    // Return an object containing the decoded values
    return { temperature, humidity, pressure, battery };
}
```

{% endstep %}

{% step %}
**Decoded payload**

```json
{
  "temperature": 123,
  "humidity": 34,
  "pressure": 29797,
  "battery": 109
}
```

{% endstep %}
{% endstepper %}

### Creating a Custom Decoder Function

{% stepper %}
{% step %}
**Select the Function Type**

1. Open the **device details page** in the Qubitro Portal.
2. Click the **Functions** tab.
3. Click **Create Function** and select **Decoder Function**.
4. Choose **Hex Payload Decoder** as the formatter type.
   {% endstep %}

{% step %}
**Write the Decoder Code**

1. Enter your custom decoder function in the editor.
2. Adjust the function to match your **device’s payload format**.
   {% endstep %}

{% step %}
**Save and Apply the Function**

1. Click **Save** to apply the decoder function.
   {% endstep %}
   {% endstepper %}

{% hint style="warning" %}
Once saved, **Qubitro will automatically apply the decoder** to all incoming data for the assigned device.
{% endhint %}


---

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