While browsing new products on AliExpress, I stumbled upon the SayoDevice OSU O3C, which bears a striking resemblance to other macro keyboards like the 4xMacropad, LILYGO TTGO T-Encoder, or T-Keyboard-S3. Yet, much like the TENSTAR T-Display, it has sold over 10,000 units on AliExpress. This prompted further investigation, revealing it is actually a Hall-effect keypad mainly designed for rhythm and single-input games such as osu! and Geometry Dash.
The keypad includes OUTEMU magnetic Hall-effect switches with rapid trigger support and a customizable actuation point as low as 0.05 mm, ensuring fast and precise keystrokes. It connects to a PC via a USB 2.0 cable, maintaining an 8,000 Hz polling rate for reduced input latency. The device features a 0.96-inch IPS color display that can show key travel information, key press counts, or custom images and text, with the first line customizable with user text. A programmable rotary knob is included for functions such as volume control or list scrolling. Additional features include custom key mapping, customizable RGB backlighting, switch calibration, support for different magnetic switches, hot-swappable keys, and configuration via a browser-based interface with firmware updates.
SayoDevice O3C specifications:
– MCU – WCH CH32V307WCU6 RISC-V microcontroller @ 144 MHz with 128KB SRAM, 192KB+288KB flash
– Type – Programmable 3-key magnetic switch keypad / macro pad
– Keys – 3x OUTEMU pink magnetic switches (hot-swappable, customizable trigger stroke down to 0.05mm)
– Display – 0.96-inch color IPS screen (Key travel visualization, key press counter, customizable text or images)
– USB – USB 2.0 Type-C port with up to 8000Hz polling rate
– Misc – Programmable rotary knob for controls (can be mapped to any function)
– Dimensions – ~65 × 50 mm (approx.)
– Material – ABS plastic keycaps with laser printing
The SayoDevice O3C can be configured via a browser-based interface on the official website, eliminating the need for a dedicated driver. The web tool allows updates, calibrates the Hall-effect switches, adjusts actuation and release parameters, configures Rapid Trigger behavior, remaps keys, and customizes RGB lighting and screen content directly from the browser.
The official firmware files are available on the company’s CDN. Additional guides for firmware updates and setup are accessible through the r/SayoDevice wiki on Reddit, YouTube tutorials for firmware updates and troubleshooting, and some GitHub repositories hosting modified firmware builds, although the official firmware sources are recommended for stability.
The SayoDevice O3C Hall-Effect keypad can be purchased from AliExpress for $26.92 or Amazon for $36.99.