CL-32 Is a Modern Pocket-Sized, E Ink-Based Computer Powered by an ESP32-S3 — with a Retro Style

After creating a series of ingenious Pi Zero-based mobile devices, Peter Barker (AKA moosepr) ventured on to a new, lower-power project. The result is the CL-32, a striking pocket-sized computer that features an ESP32-S3 SoC, E Ink display, and GPIO port for expansions.

Previously, Barker created the Pi0cket, a tiny gaming system just slightly larger than a Raspberry Pi 0. The CL-32 follows a computer-based project called Pi0CKET—Clicker, minus the Pi 0.

CL-32's appearance takes design cues from pocket computers of the 1980s. These devices generally ran a BASIC dialect and had a single-line LCD. Despite these usability challenges, many people used to have such a powerful computer in their pocket.

Instead of an LCD, CL-32 features a relatively large E Ink display that can comfortably display 38 lines with 15 characters each. The E Ink display offers several advantages over traditional LCDs, including lower power consumption, better readability in direct sunlight, and the ability to maintain the displayed image (or text) while unpowered.

Below the screen is a 72-key keyboard. Barker is still finalizing the keyboard design. Currently, there are two designs to consider. One is more conventional, with a QWERTY-style input area and a 9-digit keypad on the right. That layout might evolve into something else as Barker learns more about using the device.

The microcontroller is an ESP32-S3 module. The S3 is a dual-core XTensa running at 240 MHz with 512 kilobytes of internal SRAM. The module features 2.4 GHz Wi-Fi and Bluetooth 5 with BLE support. It sits on the back of the PCB with a micro SD card socket, USB Type-C connector, battery posts, and other devices.

A sunk-in section next to the E Ink display is the CL-32's expansion port. It contains 16 GPIOs, Power, and GND arranged uniquely. The sockets are low-profile "bottom entry" headers on the back of the PCB. Header pins connect through holes from the top side. This form factor means the easy-to-damage pins are on the inexpensive add-on board, and the layout of the headers means the board can only attach in one direction. Barker admits this choice creates another add-on form factor, but the intention is to make CL-32 more robust in educational environments.

The off-the-shelf BP-4L LiPo has a capacity rating in the 1200 to 1500 mAh range. With this battery, Barker estimates that the CL-32 could provide days of coding fun for its user.

One aspect that is unclear about the CL-32 is what runs on the ESP32-S3. This versatile microcontroller could run a variety of operating environments, including MicroPython, a custom code, or maybe it leverages Clem Meyer's work to make Linux bootable on an ESP32-S3. Regardless of the choice, we look forward to seeing more details as this project (or product?) evolves.

For more information, visit CL-32's website and sign up for email notifications. You can also see a few details on this project page. Last, the X/Twitter #pi0cket has some detailed posts.