The simplest, quickest, and most effective way to create your own Felini is to have the 3D casing manufactured based on the file I provide, using 3D printing with laser sintering or resin to achieve high-detail casing components. For the PCB, you should follow a similar process, outsourcing double-sided SMT assembly for the relatively straightforward device. Lastly, you just need to solder the pins onto the circuit board and assemble the components together with a bit of skill; I think it's easier than assembling LEGO. Good luck!

Felini uses esp32s3, so it can load firmware directly via USB port without the need for an external loading circuit. Please use esp-idf or esp flash tool to load the code. Normally, Felini will appear as a COM port accompanied by a USB JTAG/serial debug unit as shown below. With this status, you can load the new firmware without making any changes.

However, when using applications related to USB ports such as DAPLink, Logic Analyzer, FELINI will automatically convert to drivers for these applications. In this case, to load the code, please exit the above applications and return to the main screen.
In case of firmware error, the simplest way is to hold down the power button for 10 seconds to power off the device. Then turn it back on. If you still don't see the COM and USB JTAG/serial ports for loading code. Power off the device again, then hold down the middle button of the rotary encoder, at the same time, press the power button to turn on FELINI. At this time, FELINI will be in bootloader mode and ready to download new firmware. This is the boot mode mechanism through GPIO 0 of the esp32s3 (the encoder is connected to this pin). This ensures that in all cases, your FELINI cannot be bricked. Good Luck ^^

For the device case, you can use one of the following two printing technologies: MJF laser sintering printing (Nylon) or UV resin printing. Resin printing will give a sharper surface, but you must attach glue to the nut. For MJF, you can heat the nut submerged into the molten plastic. Personally, I like MJF better.