Gremoire

Building Your Own USB Typing Stick ​

A USB typing stick is a tiny device that pretends to be a keyboard when plugged into a computer. Instead of waiting for you to press physical keys, it automatically types out whatever script you’ve programmed into it. This simple trick opens a whole world of possibilities, from automation and testing to creative experiments with computer input.

What makes this device powerful is its ability to act as a USB Human Interface Device (HID). Computers naturally trust HID devices, so when your microcontroller announces itself as a keyboard, the system accepts it without hesitation.

Choosing the Microcontroller ​

The heart of the USB typing stick is the microcontroller. You need a chip that supports USB device mode, allowing it to impersonate a keyboard.

Common options include:

  • Arduino Pro Micro (ATmega32U4) – Compact, inexpensive, and HID-ready.
  • Teensy boards – Extremely capable and very small.
  • Raspberry Pi Pico (RP2040) – Affordable, powerful, and supports HID through MicroPython or C++.

Each of these can be programmed to send keyboard input the moment the device receives power.

Programming the Device ​

On an Arduino Pro Micro, for example, programming the stick is as simple as writing a small sketch. Using the built-in Keyboard library, you can instruct the device to type any text automatically.

Here is a simple example:

#include <Keyboard.h>

void setup() {
  delay(2000); // give the OS time to detect the device
  Keyboard.print("hello world");
}

void loop() {}

After uploading this code, the device will begin typing "hello world" as soon as it's plugged into a computer.

Making It Look Like a USB Stick ​

Once the firmware works, the next step is creating a compact form. You can solder the microcontroller directly to a USB male connector or mount it inside an old USB flash drive case.

Common enclosure options:

  • A gutted USB flash drive housing
  • A small 3D-printed case
  • A USB male plug adapter
  • Heat-shrink tubing for a minimalist build

The goal is a clean, durable device that plugs in like a regular flash drive.

Creating a Programmable Version ​

Instead of recompiling code every time you want to change the script, you can create a version that loads a text file and types its contents.

Using a Raspberry Pi Pico and MicroPython, you can store a file named payload.txt on the device. The firmware reads the file and types its contents automatically.

A simple MicroPython script looks like this:

import time
import usb_hid
from hid_keyboard import Keyboard

kbd = Keyboard(usb_hid.devices)

time.sleep(2)

with open("payload.txt") as f:
    for line in f:
        kbd.print(line)

Updating the typed script becomes as easy as editing a text file.

Expanding the Capabilities ​

Once the basic typing stick works, there are many creative upgrades you can explore:

  • Add multiple modes using a physical switch.
  • Include an LED indicator to show the device is active.
  • Store multiple payloads on a microSD card.
  • Use a WiFi-enabled microcontroller to change scripts remotely.
  • Add a tiny OLED display to select scripts before typing.

These enhancements turn the simple USB typing stick into a highly flexible automation tool.

Final Thoughts ​

Building a USB typing stick combines electronics, programming, and a bit of imaginative hardware design. Whether you’re automating repetitive tasks, experimenting with HID behaviors, or just enjoying the engineering challenge, this project opens the door to a strange and delightful corner of microcontroller creativity. The next step is tailoring it to your own needs, transforming it from a simple gadget into a tool that reflects your approach to automation.