HPWriter - Silent Digital Typewriter

A modern, silent typewriter that prints on plain paper using an HP45 inkjet cartridge. Features instant boot, USB keyboard input, USB flash drive support, and ultra-quiet operation.

A modern, silent typewriter that prints on plain paper using an HP45 inkjet cartridge. This project explores a practical “digital typewriter” that behaves like a real appliance — no operating system, no laptop required.

Project Overview

HPWriter is designed to solve the problem of noisy, distracting typewriters in classroom settings, while providing a distraction-free writing experience that produces real ink-on-paper output.

Key Features

  • Instant boot (ESP32-S3 microcontroller)
  • USB keyboard input for typing
  • USB flash drive support (save / load text files)
  • Plain text editor + print buffer
  • Real ink-on-paper, not thermal
  • Ultra-quiet motion (NEMA-14 steppers + TMC drivers)
  • Dedicated HP45 inkjet controller for microsecond firing pulses
  • Portable, battery powered
  • Serviceable and long-lived design philosophy

Motivation

Traditional analog typewriters are too noisy and distracting for classroom use, while iPads and laptops can be distracting for both students and teachers. HPWriter provides a silent, distraction-free, battery-powered typewriter with keyboard input for students who want to type in class without the noise distraction.

Technical Specifications

  • Print Resolution: 300 DPI equivalent (HP45 native resolution)
  • Character Spacing: 10 CPI or 12 CPI (user-selectable)
  • Line Spacing: 6 LPI or 8 LPI (user-selectable)
  • Paper: Standard plain paper (20–24 lb bond recommended)
  • Ink: HP45 compatible ink cartridges
  • Control: ESP32-S3 microcontroller
  • Motion Control: NEMA-14 steppers with TMC drivers

Where This Device Excels

  • Libraries and quiet spaces: Silent operation allows typing without disturbing others
  • Focus writing sessions: No internet, notifications, or apps to distract
  • Journaling and personal writing: Physical output provides a tangible record
  • Field research and note-taking: Battery-powered portability for on-site documentation
  • Creative writing retreats: Distraction-free environment for deep work

Advantages Over Existing Solutions

Unlike digital-only typewriters (Freewrite Smart, Alpha Typewriter) or older thermal paper machines, HPWriter offers:

  • ✅ Real ink on paper (non-toxic, standard paper)
  • ✅ Modern, open-source design
  • ✅ File export capability
  • ✅ Multiple modes and programs
  • ✅ Interactive CLI interface
  • ✅ Serviceable and long-lived design

Repository

The complete source code, documentation, bill of materials, and project plans are available in the HPWriter repository.