FreeQuay is a keyboard translation tool designed primarily to replicate the behavior of devices like the Hasu USB-to-USB converter.
FreeQuay is built on four guiding principles:
Ease of use
Cost-effectiveness
Expandability and customizability
Sustainability
Every decision in this project is driven by these principles.
https://1upkeyboards.com/shop/controllers/usb-to-usb-converter/
The Hasu USB-to-USB converter was the original device for a project like this. However, it suffers from two major flaws:
It was expensive (retail $72+).
It is nearly impossible to purchase these days.
This scarcity and price come down to hardware choices; relying on an ATmega-based microcontroller and the MAX3421 USB chipset makes high costs inevitable.
The RP2040 and RP2350 microcontrollers used in Raspberry Pi Picos are an excellent choice for making a keyboard translation tool. They were designed from the ground up to run interpreters like MicroPython. They have plenty of memory, utilize cheap off-chip flash, boast fast clock speeds, and offer plenty of interfaces for the end user.
Using one of these boards allows you to run KMK—a Python-based keyboard firmware that lets the end user program macros directly in Python. This is an extremely powerful tool that many other macropads lack.
Projects such as [Project Name] allow a user to create a keyboard converter using two Raspberry Pi Picos. While this is a great concept, it fails on one major front: it is not end-user friendly to set up.
[https://www.adafruit.com/product/5723]
This board is an effective contender. However, the Adafruit board is a premium product, and as such, it fetches a premium price tag.
https://www.waveshare.com/rp2350-usb-a.htm
The Waveshare RP2350-USB-A is an excellent little board with a great feature set and an attractive price. Unfortunately, there is a hardware "bug" on this board that requires the user to physically desolder a resistor in order for it to work.
https://gitlab.com/lykt/kite
Kite is an excellent hardware demonstration of a CH32 microcontroller being used for a USB keyboard conversion project.