Making a thread to get a bit of visibility and maybe some input from people, but over the last week I've been working on reverse engineering parts of the Joy-Con communication methods, and so far I've had success talking straight with the rails using UART and an ESP32, and more recently, HID via Joy-Con Charging Grip. Contrary to the name, the Joy-Con charging grip actually does quite a bit more than charge. Plugging it into a computer exposes two USB interfaces (one per Joy-Con) with two endpoints which can be talked with via the HID protocol. By dumping the firmware of the STM32 chip on the charging grip I've also managed to reverse engineer the custom HID commands which allowed me to talk more extensively with the Joy-Con. My code repository for my HID Joy-Con research can be found at https://github.com/shinyquagsire23/HID-Joy-Con-Whispering. Currently it is untested with a Pro Controller, but it has the same STM32 chip as the grip and the firmware is similar, so if anyone has a Pro Controller and wants to try seeing if it works with one, feel free. What can it do now? Currently with what I have, the following is already done: Retrieving full input packets from each Joy-Con, including analog joystick values, buttons, etc. Joy-Con SPI firmware dumping. Since UART commands exist to read from the SPI firmware, and the HID protocol exposes a command to send UART commands, the entirety of the Joy-Con on-board SPI flash can be dumped with only a charging grip What else is possible? Anything which the Joy-Con can do while clicked into console should be possible. This includes HD rumble, NFC, IR, and other things. It should also be possible to write Linux or maybe Windows drivers which can interact with the Joy-Con over HID so that the device can act as a single controller with what is already done. What needs to be done? There are still a lot of unknowns with the wired UART protocol, specifically with most of the extra peripherals like HD rumble. The best way to document these, unfortunately, is by using a logic analyzer to watch the UART communication while it is attached to a console, but dekuNukem has already done a lot of this at his repo here. Additionally, it seems despite Bluetooth using HID, the USB-C HID protocol is not the same as the Bluetooth protocol, which means that reversing Bluetooth will take either Switch privilege escalation or Joy-Con firmware reverse engineering.