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This development board features the cheap CH32V003F4U6 RISC-V microcontroller by WCH with a up to 48 MHz clock frequency, 16KB of Flash and 2KB of RAM. With its tiny size of only 16x26mm, it fits great on a breadboard with three rows available on each side! It has an external crystal populated by default which can be removed and bypassed with a solder bridge.

13 (15 with crystal pins) of the 18 GPIOs are directly accessible from the side pins.

It has a User LED at PC0 and and User Button at PD7 (also used for Reset functionality).

The main advantage apart from the small size is the ability to use bitbanged USB with the rv003usb stack by CNLohr! So this board is a perfect plug-and-play platform for creating USB peripherals.

Three of the 18 possible GPIOs are used for USB functionality. The USB data lines can be probed with the two through-holes on the inside.

This board is fully compatible with the open source ch32v003fun project.

The PCBs of this revision were manufactured by our partner AISLER.

Each board is assembled by hand and tested for basic USB and GPIO functionalities.

IMPORTANT: To program this board, you will need a compatible SWIO programmer, for example the WCH LinkE. Other programmers, for example with a ESP32-S2 is described here. You can also program it with an AVR-based ATMega328P (Arduino Uno R3, Nano, ...) using the project Ardulink.

The whole PCB design is open source with the CERN-OHL-W-2.0 license and available on GitHub!

Disclaimer: This board is intended only for development and evaluation purposes.

Settings used for RV003USB usb_config.h file:

• define USB_DM 3

• define USB_DP 4

• define USB_DPU 2

• define USB_PORT D