How to Create an App

The WebSDR platform allows users to:

✅ Use ready-to-use applications

✅ Modify existing applications

✅ Create new applications from scratch using function blocks

In this section, we’ll walk through creating a Spectrum Waterfall application, demonstrating the platform’s core principles.

Core Principle

🔹 Every General or Sink block requires a UI block to display its output on the grid.

Step 1: Create a New Project

  • Click Create Project and enter a name.

  • Switch to Edit Mode (for block configuration).

edit mode

Understanding the Grid System

../_images/grid.jpg

  • The Grid block is the main canvas of your application.

  • By default, it consists of 10 columns × 10 rows (modifiable in the Layout tab).

  • Click Save to apply any changes.

../_images/save.jpg

Step 2: Add a Signal Source

  • Drag the Web USB Source block from the General category.

  • Set its parameters or leave them as default.

Add a UI “Source Select” block:

  • Assign a caption.

  • Enable USB (usbs) to activate the USB device.

../_images/drag.jpg

Open the Layout Tab:

  • Set the location of the Source Select dialog box.

  • Click Save and switch to Play Mode to verify the interface.

Note

Parameters can be set as fixed values or controlled dynamically using functions.

Step 3: Establish Connections

To ensure the SDR device is recognized:

  • Connect Device (WebUSBSource) → Device (SourceSelect).

Set up SDR Start/Stop Control:

  • Connect Started (Grid) → Disable (Source Select).

  • Connect Source Selected (Source Select) → Enable Control (Grid).

../_images/establish.jpg

Step 4: Add Input Controls

To allow frequency control via UI:

  • Drag an Input block and select Frequency as the format.

  • Define Value / Min / Max / Step (Hz, MHz, GHz).

Connect:

  • Value (Input_Frequency) → Frequency (WebUSBSource).

  • Min/Max parameters → WebUSBSource.

  • Control_Source_Select (SourceSelect) → Disable (Input_Frequency).

  • Open the Layout Tab, drag it to position, and click Save.

../_images/add_input.jpg

🔹 Repeat these steps for any additional input controls.

Step 5: Add Signal Visualization (Waterfall Display)

To visualize SDR output:

  • Add a WaterfallSink block.

Connect:

  • Out (WebUSBSource) → In (WaterfallSink).

  • Rate (WebUSBSource) → Rate (WaterfallSink).

Add a UI “Canvas” block:

  • Link Canvas (WaterfallSink) → Canvas (UI Canvas Block).

../_images/waterfall.jpg

Layout Tab:

  • Position WaterfallSink below the control menu.

  • Resize it for display.

  • Click Save.

../_images/wf_s_lay.jpg

Step 6: Test the Application

  • Switch to Play Mode.

  • Select the Source.

  • Click Play.

../_images/app_b_final.jpg

  • Use mouse scroll to change the frequency dynamically.

Tip

Want to learn more?

  • Check the ready-to-use apps in Edit Mode.

  • See which blocks were used.

  • Copy parts into your own app.