Walabot Touchpad: Transform Any Surface into a Wireless Touch Interface

The Walabot Touchpad is a sleek, low‑profile system that converts any flat surface into a responsive touchpad for your laptop. Imagine turning a book, a table, or a wall into a touch interface—no wires, no extra hardware. By pairing Walabot’s 3‑D microwave imaging with projector technology, you can project touch‑screen functionality onto virtually any surface.

Designed for everyday practicality and universal accessibility, the solution relies on a Raspberry Pi 3 client that reads data from a Walabot Creator sensor and communicates with a host computer via local Wi‑Fi. The system operates through simple socket protocols, keeping setup minimal while maintaining imaging accuracy.

How It Works

The workflow is straightforward:

The Raspberry Pi triggers the Walabot sensor.
Walabot detects and locates the target (typically a finger).
The Pi processes the target data, determines the user action, and sends the command to the host over Wi‑Fi.
The host machine receives the command and controls the cursor using PyAutoGUI.

Demonstration

In Progress

Setting Up the Raspberry Pi

Follow these steps to prepare your Pi and install the Walabot SDK:

Install Raspbian (now Raspberry Pi OS) using NOOBS or download it directly from the official Raspberry Pi website.
For headless operation, enable VNC or SSH and consider adding a shutdown button.
Leave the header pins unsoldered if you don’t need I/O.
Insert the SD card, connect the Pi to a display and power, and boot up.
Connect to the internet and launch Chromium.
Navigate to the Walabot download page and download the Raspberry Pi installer.
Open a terminal and run the following commands:
```
sudo apt‑get update
cd Downloads
sudo dpkg -i walabot_maker_1.0.34_raspberry_arm32.deb
```
These commands update package lists and install the Walabot SDK.
After the installation, upgrade the system and reboot:
```
sudo apt‑get dist‑upgrade
sudo reboot
```
To improve performance, disable the desktop GUI if you won’t be using the Pi interactively.

Walabot Interfacing

Walabot is a 3‑D microwave imaging sensor capable of tasks such as breathing monitoring, through‑wall sensing, and multi‑target detection. For the touchpad, its RF 3‑D sensing delivers precise x, y, and z coordinates of a target. Dynamic filtering removes static reflections, allowing accurate tracking even behind materials.

Because Walabot draws 400–900 mA, the Pi’s default USB output is insufficient. Add the line max_usb_current=1 to /boot/config.txt to raise the limit to 1200 mA.

Target Detection

Ensuring the sensor registers only the intended finger is critical. I used the GetSensorTargets() API function, disabled MTI mode, and capped the detection radius at 10 cm. The sensor returns x, y, z, and amplitude; only x and y are used for cursor mapping.

Because the sensor operates in polar coordinates (r, θ, φ), I measured the extreme x and y values to define the usable arena. During setup, the program automatically detects these bounds by sliding a finger across the surface.

Action interpretation:

One contact point → cursor movement.
Two contact points → right‑click.
Three contact points → left‑click.

Fine‑tuning the z‑range proved challenging; reducing the arena size made the touchpad too small, while filtering high‑z targets caused instability. The optimal solution is a curved touchpad matching Walabot’s detection profile or upgrading to the Walabot Developer Edition.