Tiny credit card computer features eInk screen and is just 1mm thick

At a glance:

• The Muxcard is a fully functional computer designed to match credit card dimensions with an eInk display
• It's powered by an ESP32-C3 microcontroller with NFC, sensors, and a 1mm thick battery
• The current prototype is 1mm thick, slightly exceeding the standard 0.76mm credit card thickness

What is the Muxcard?

The Muxcard represents a remarkable achievement in miniaturization, bringing together cutting-edge components in a form factor that mimics the ubiquitous credit card. Created by krauseler and shared on GitHub, this device demonstrates how modern electronics can be compressed into incredibly small spaces while maintaining full functionality. The project is inspired by the long-standing goal among tech enthusiasts to create a computer that fits perfectly within the dimensions of a standard credit card, a challenge that has fascinated device makers for decades.

This isn't the first time credit card-sized computers have captured imaginations. The iconic Raspberry Pi began as a credit card-sized barebones computer concept, and many of us remember purchasing credit card-sized calculators in previous decades. However, previous attempts often overlooked the crucial third dimension—thickness—that makes credit cards so portable. The Muxcard addresses this limitation head-on, with its creator admitting the prototype is 1mm thick, just slightly exceeding the official ISO/IEC 7810 ID-1 standard of 0.76mm.

Technical specifications

The Muxcard packs an impressive array of components into its ultra-slim profile. At its heart is the ESP32-C3 microcontroller, a RISC-V CPU architecture chip that includes Wi-Fi capabilities, 320KB of usable SRAM, and 384KB of ROM. This provides enough processing power for various applications while maintaining the device's minimal footprint. The display is a 1.54-inch flexible ePaper screen with 200x200 pixel resolution and partial update support, which is ideal for low-power applications that don't require frequent full screen refreshes.

For connectivity and sensing, the Muxcard includes an RC522 NFC read/write module (not just a passive tag) and a LIS2DW12 accelerometer for wake triggers and motion sensing. Powering this entire system is a 30mAh, 1mm thick rechargeable LiPo battery. The creator ingeniously repurposed an old plastic NFC card with most of its volume cut away as the Muxcard's chassis, demonstrating creative problem-solving within extreme spatial constraints. While the current prototype is acknowledged to be somewhat fragile, it already functions as a complete, albeit minimalist, computer system.

Future improvements and potential uses

Despite its impressive current state, the Muxcard project is still evolving. The creator has outlined several planned enhancements to bring the device closer to its ultimate vision. These include adding USB Type-C for charging and data transfer, integrating a microSD card slot for expanded storage, implementing touch button controls for user interaction, and potentially adopting an even slimmer LiPo battery cell. Each of these improvements presents significant engineering challenges given the device's already minimal thickness.

The potential applications for such a compact computer are diverse and intriguing. The creator envisions uses including a smart-home dashboard, offline storage for two-factor authentication (2FA) codes, backup keys and passwords, and other security-related applications. The device's ultra-thin profile allows it to be carried in a wallet or cardholder without adding noticeable bulk, making it ideal for situations where both portability and functionality are critical. The creator is actively seeking collaboration and contributions from the community to help realize the full potential of this innovative device.

Why it matters

The Muxcard represents more than just a technical curiosity; it exemplifies the ongoing trend of miniaturization in computing that has defined much of technological progress. As devices become increasingly powerful yet smaller, they enable new form factors and applications that were previously impossible. This project demonstrates how even hobbyists and independent developers can push the boundaries of what's possible with off-the-shelf components and creative engineering.

For the average consumer, the Muxcard hints at a future where powerful computing becomes truly ubiquitous and invisible. Imagine having a fully functional computer that fits in your wallet, ready to serve as a backup authentication device, a portable storage solution, or a specialized tool for specific tasks. As the creator notes, there's something almost magical about holding what feels like a normal credit card that can actually compute and display information. This blend of familiarity and innovation is what makes projects like the Muxcard both technically impressive and culturally significant.