The gamepad includes a Broadcom BCM4319 wifi card for network communications.

It is accessed over SDIO.

The driver used in the stock gamepad firmware is a port of open-source BCM43xx drivers.

The gamepad's wifi card uses the Broadcom BCM4319 SoC. Broadcom hardware is poorly documented, but open-source drivers can be found for it.

Two types of firmware exist for Broadcom wifi cards: soft-MAC and full-MAC. The former means a minimalistic firmware, with most of the functionality implemented in the driver. The latter means a lot of functionality is instead implemented in the firmware, allowing for a simpler and smaller driver. The gamepad uses a full-MAC firmware.

In theory, the BCM4319 supports both 5 GHz and 2.4 GHz bands. In practice, the gamepad's wifi card includes only a 5 GHz amplifier, which makes it incompatible with the 2.4 GHz band. (https://gbatemp.net/threads/hacking-the-wiiu-gamepad.661890/post-10593876)

The BCM4319's firmware is loaded from Flash upon boot.

So far, the following peculiarities have been observed with this firmware:

• It only supports the 5 GHz band.
• It has a custom WPA implementation. It doesn't support standard WPA.

Non-Nintendo BCM4319 firmwares can be found online, and function to some extent. They're the opposite of the Nintendo firmware in that they only support the 2.4 GHz band. They perform very poorly on this band – they may be able to receive packets sometimes, but they don't perform well enough to establish any connection.