nanoCH32V203 VS Pico-PIO-USB

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.

I know that I can have multiple ports using https://github.com/sekigon-gonnoc/Pico-PIO-USB, but I wanted to know if I could make one port a device and the other a host at the same time using the given PIOs and state machines.

I think a PIO based USB driver is a better approach, but someone needs to do the work of porting that to Ada.

That would be Pico-PIO-USB library or some people combine two Pico boards (or one board with two RP2040 MCUs).

If you need both device and host interfaces at the same time, then you can either use Pico-PIO-USB library or combine two Pico boards (or one board with two RP2040 MCUs).

However, not so many microcontrollers can easily do USB keyboard input (host) and output (device) at the same time, if that's what you need. You could look at the Teensy 4 or Teensy 4.1 for example. There might be other Arduino-compatible boards that can do it, I'm not sure which. Apparently it's also possible on the Pi Pico with this project: sekigon-gonnoc/Pico-PIO-USB: USB host/device implementation using PIO of raspberry pi pico (RP2040). But that's a bit of an advanced hack, and I can't tell you how well it works.

Maybe you could use something like this: https://github.com/sekigon-gonnoc/Pico-PIO-USB

you should check out https://github.com/sekigon-gonnoc/Pico-PIO-USB for someone that has implemented USB chaining with rp2040. unfortunately it uses up both PIOs.

The pico just seems to be a flexible cheap option for USB applications. An example https://github.com/sekigon-gonnoc/Pico-PIO-USB

Highly experimental for advanced users. Adds a second USB port to Pi Pico using the PIO controller so the pico can connect to a PC and keyboard at the same time. https://github.com/sekigon-gonnoc/Pico-PIO-USB

watch the video to see this non-qmk firmware for the Rasberry pi Pico used to daisy chain devices with fixed device and host ports https://github.com/sekigon-gonnoc/Pico-PIO-USB