# How to Publish and Decode Multiple Hex Payloads via MQTT on Qubitro
This guide shows how to:
* ✅ Send multiple hex payloads using **MQTTX**
* ✅ Use a custom **Qubitro** [**Decoder Function** ](https://app.gitbook.com/s/fQfo4zX1x0hfOimS9E2u/platform/functions/decoder-function#hex-payload-decoder)to decode GPS and sensor data
* ✅ View structured decoded data in the Qubitro portal
***
### 🧩 Prerequisites
* A [Qubitro account](https://portal.qubitro.com/)
* An existing **Device**
* [MQTTX Desktop App](https://mqttx.app/)
* Your device's **MQTT credentials**
***
### Step 1: Get Your Qubitro MQTT Credentials
1. Go to your device in the **Qubitro Portal**
2. Click the **MQTT Credentials** tab
3. Copy:
* **Device ID** (used as `Username` and topic)
* **Device Token** (used as `Password`)
* **Host**: `broker.qubitro.com`
* **Port**: `8883` (SSL) or `1883` (non-SSL)
* **Topic**: `Device ID`
***
### Step 2: Configure MQTTX (Secure Connection)
Open MQTTX and configure your connection as shown below:
* **Name**: `broker.qubitro.com`
* **Host**: `mqtts://broker.qubitro.com`
* **Port**: `8883`
* **Client ID**: (same as Device ID)
* **Username**: Device ID
* **Password**: Device Token
* **SSL/TLS**: ✅ Enabled
* **SSL Secure**: ✅ Enabled
* **Certificate**: `CA signed server certificate`
{% hint style="success" %}
Click **Connect** to establish a secure MQTT connection.
{% endhint %}
***
### Step 3: Add Decoder Function in Qubitro
1\. Go to your device → Functions tab
2\. Click Add Function → Choose Decoder Function
3\. Paste the following JavaScript code:
```javascript
function decoder(input) {
const longitude = ((input.bytes[0] << 24) | (input.bytes[1] << 16) | (input.bytes[2] << 8) | (input.bytes[6] & 0xC0)) /1000000;
const latitude = ((input.bytes[3] << 24) | (input.bytes[4] << 16) | (input.bytes[5] << 8) | ((input.bytes[6] & 0x30) << 2)) /1000000;
const hMSL32 = ((((input.bytes[6] & 0x0F) << 8 ) + input.bytes[7]) * 2) - 191;
const hAccCoeff = (input.bytes[8] & 0xE0) >> 5;
const vAccCoeff = (input.bytes[8] & 0x1C) >> 2;
const heading = ((input.bytes[8] & 0x03) << 2) + ((input.bytes[9] & 0xC0) >> 6);
const speed = (input.bytes[9] & 0x3F);
const battery = ((input.bytes[10]*256) + input.bytes[11]);
const year = (input.bytes[12] >> 2) + 2000;
const month = ((input.bytes[12] & 0x03) << 2) + ((input.bytes[13] & 0xC0) >> 6);
const day = (input.bytes[13] & 0x3E) >> 1;
const hour = ((input.bytes[13] & 0x01) << 4) + ((input.bytes[14] & 0xF0) >> 4);
const minute = ((input.bytes[14] & 0x0F) << 2) + ((input.bytes[15] & 0xC0) >> 6);
const second = (input.bytes[15] & 0x3F);
const timestampSeconds = Math.floor(new Date(year, month, day, hour, minute, second).getTime() / 1000);
return {
longitude,
latitude,
coordinates: [latitude, longitude],
hMSL32,
hAccCoeff,
vAccCoeff,
heading,
speed,
battery,
time: timestampSeconds
};
}
```
{% hint style="success" %}
You can also test a single hex payload on the Qubitro Portal to verify your decoder.
{% endhint %}
4. Save and activate the function.
### Step 4: Publish Multiple Hex Payloads
1. Go to the **Publish** tab in MQTTX.
2. In the **topic** field, paste your **Device ID**.
3. Set the payload type to **JSON**.
4. Use the following payload:
```json
{
"payload_hex": "00C08802808560A184000FFB648EAD0F,00c088028085909784000ffb648ead46,00c089028085109284000ffe648ead89,00c088028085e09c84000ffe648eadcb"
}
```
5. Click the green send button to publish the message.
### Step 5: View Decoded Data
Open the Storage tab in your Qubitro device and you’ll see structured decoded values like:
***
You’ve successfully:
• Connected MQTTX to Qubitro securely
• Published multiple hex payloads
• Used a custom decoder to parse sensor/GPS values
• Verified decoded output in Qubitro