Tindie recently listed Comu, a compact development board built around the WCH CH32V203 RISC-V microcontroller. Measuring 13 × 9.4mm, the board fits inside a USB-A port and combines programmable touch controls, LEDs, USB device support, and access to several GPIO signals.

The CH32V203 operates at up to 144MHz using its internal oscillator and provides 224KB of application flash, 24KB of boot flash, and 20KB of SRAM. Other integrated features include a 12-bit ADC, DMA controller, touch-sensing hardware, and a full-speed USB peripheral.

CH32V203 block diagram
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Comu includes four capacitive-touch inputs formed along the castellated board edges, along with two white LEDs. Six additional GPIO pins are exposed through test pads, allowing the board to be incorporated into other hardware or used for compact embedded experiments.

The board connects directly to a USB-A port and can operate as a USB Human Interface Device. Suggested applications include keyboard macros, volume controls, screen-capture buttons, computer sleep controls, and other programmable shortcuts. Its USB peripheral can also be accessed at a lower level for experimenting with raw USB packets and inspecting traffic using tools such as usbmon and Wireshark.

Comu top and bottom view
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A custom 2KB USB bootloader is installed at the factory. Because the board lacks a dedicated BOOT0 button, the bootloader remains active for five seconds after connection before launching the user application. Programs are linked and flashed at address 0x800, with the supplied Makefiles handling the required offset.

Comu demo
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The primary development environment is ch32fun, a lightweight framework for bare-metal C and C++ development on WCH microcontrollers. The project repository includes examples for blinking the LEDs, capacitive-touch input, formatted output, USB TTY, USB HID, and USB mass-storage operation.

Alternative development options include Rust through ch32-hal, Arduino through arduino_core_ch32, WCH’s HAL and MounRiver Studio II, and USB libraries such as TinyUSB.