Show HN: Hacking a $20 4G wireless hotspot into a texting device
A developer creatively hacks a $20 4G wireless hotspot, an iPhone keyboard, and a SHARP memory display into a unique texting device. The detailed build log showcases impressive hardware modification, custom PCB design, and intricate kernel driver development. This project exemplifies the DIY spirit and technical prowess often celebrated on Hacker News, transforming mundane components into something new and functional.
The Lowdown
The author documents the transformation of a $20 4G wireless hotspot into a custom texting device, born from a collection of random parts on their desk. This ambitious project involved repurposing components like an expensive iPhone keyboard and a SHARP memory display, showcasing a significant engineering effort in hardware and software integration.
- Component Assembly: The project creatively combines an inexpensive, unlocked 4G modem (MF800) running Android, an iPhone Clicks Keyboard requiring physical modification, and an Adafruit SHARP Memory Display.
- Software Foundation: The author details the process of installing Linux on the MF800 using the OpenStick project, extracting original device trees, and navigating initial driver challenges.
- Custom Hardware Integration: A bespoke adapter PCB was designed to manage power, USB host/device switching, display power, and signal level conversion, crucial for linking the disparate components effectively.
- Physical Modification: The MF800's PCB was surgically cut and re-wired to achieve the desired compact form factor, fitting it within the iPhone keyboard's constraints.
- Wiring and Debugging: The build involved extensive wiring, testing, and debugging, particularly for USB connectivity (including a clever twist-wire fix for high-speed USB issues) and SPI communication with the display.
- Kernel Driver Development: A custom kernel driver (ardangelo's sharp-drm-driver) was adapted and patched to enable the display, incorporating dithering for improved video and image rendering.
- Enclosure Design: Multiple 3D-printed enclosure iterations were developed to house the custom electronics neatly within the keyboard case, overcoming physical fitment and display placement hurdles.
- Future Enhancements: Ongoing work includes implementing proper sleep functionality, exploring additional input methods like a touchscreen or scroll wheel, and integrating sound or vibration feedback.
- Open Source Contribution: All design files, code, and documentation are made publicly available on GitHub, encouraging replication and further development by the community.
This detailed build log serves as an inspiring example of how resourcefulness, technical skill, and a "caveman brain" can transform disparate, inexpensive components into a highly personalized and functional piece of technology, pushing the boundaries of what's possible with DIY electronics.