ch32v003 VS nanoCH32V203

There are some MCUs that use RV32E also - the CH32V003 [0] comes to mind.

[0] - https://github.com/openwch/ch32v003

Higher interest in the mechanical issue. Kailh box aren't made for 5050-equivalent-sized LEDs so the best I can come up with is placing them on a daughter board with some distance and just accepting losing some light. Probably will use a low-cost microcontroller and R2R leader (current sink) to make them addressable. Alternatively, make use of the 11 bit PWM and LC filter while the ADC forms the feedback loop. Currently unsure if I go with WCH CH32V003 (https://github.com/openwch/ch32v003) or Padauk MCUs. A couple of kHZ PWM should be fine but if I make a PCB I might as well just go all in with PWM-free.

If you are willing to try r/RISCV ones, then nanoCH32V203 (with two Full-Speed interfaces) and nanoCH32V305 (with one Full-Speed and one High-Speed interface) might be enough.

There are dual USB r/RISCV boards with GPIO pins exposed, like nanoCH32V203 and nanoCH32V305.

Another alternative is to use dual USB MCU board like nanoCH32V203 as USB CDC relay.

RISC-V boards cost $3-$6 depending if you want high speed USB or full speed one.

Their earlier boards like nanoCH32V203 and nanoCH32V305 were more user friendly, one could flash those via USB without WCH-Link.

Muse Lab has MCU boards like nanoCH32V203 and nanoCH32V305.

The same form factor as nanoCH32V203, but with more RAM and storage, also one of USB interfaces is high speed and SDIO is native this time. Comparable to CH32V307 boards, but lacks ethernet port.

Speaking of hardware there is very nice $3 RISC-V board that would fit well USB to USB converter use case. No keyboard firmware is ported to it yet.