# Snapshot Tool
In the context of CAN bus logging, a snapshot file refers to a JSON-formatted file containing a periodic sample or "snapshot" of decoded CAN bus data for select CAN signals of interest.
The steps below help you transmit a periodic sample of decoded CAN bus data for select CAN messages of interest in JSON format.
{% hint style="info" %}
#### Notes:
* Before you begin these steps, add and enable AWS configuration for the ReXgen logger.
{% endhint %}
Drag the Snapshot tool in the Transmitting section in the configuration window.
* This opens the Snapshot window
**Add Snapshot File:** Users can add and name a new snapshot file.
**Remove Snapshot File:** This allows users to remove an existing snapshot file.
**Add Items:** This allows users to add items to a snapshot file.
**Remove Items:** This allows users to remove items from a snapshot file.
Click on the ‘Add Snapshot File’ tab –
* Enter the desired name, sampling rate (sec) and upload rate, and click OK.
Once the name of the Snapshot file is assigned, click the ‘Add Items’ tab to add the required items to the snapshot file.
#### **(a) Add Signals:**
* Add signals from the existing DBC file by clicking on the check box beside them.
{% hint style="info" %}
#### Note:
* One snapshot file supports only fourteen (14) items.
{% endhint %}
OR
To add a new dbc file, click on the folder icon, select the desired dbc file containing the parameters, and click ‘Open’.
Select up to fourteen items and click ‘OK’.
Once the items are added to the snapshot file, specify the CAN source for each item separately.
#### (b) Add Internal Channels
Add internal channels by checking the checkboxes beside them, then click OK.
Click “Run” to update the configuration. 
* The configuration will be loaded into the data logger and will immediately start uploading to the S3 bucket.
* The snapshot file is stored in the ‘Root’ folder inside your S3 bucket.
Open the root folder to view the snapshot file.
* The file is stored in ‘.json’ format.
View the live value updates of the configured snapshot parameters in the snapshot .json file.
{% hint style="info" %}
#### Note:
* Snapshot is limited to 1 file with 13 items.
* Multiplexes signals are not supported.
{% endhint %}
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