Wireless with 32u4

[Merlin04]

I know the 32u4 doesn't have a hardware encryption module, but could you use an external chip?

[ahtn]

It's possible to use a software implementation of AES. I want to be able to support nRF24 + 32u4 as an alternative wireless receiver option. In the legacy atmega8 version the code uses a software implementation of AES.

To use it as a wireless keyboard in the same way as the xmega is a bit harder, but still possible. A couple of limitations:

• Need to use a 3.3V @8MHz board. Would need to use a Li-Ion battery for power.
• For the device to enter sleep mode, it needs to setup interrupts on it's column pins so it can detect when a key is pressed and wake up from sleep mode. The 32u4 can't assign pin interrupts on all of its IO pins, so have to pick the column pins carefully.
• Might need to disable some features to fit into 32kB flash. If using the 1kB kp bootloader, with software AES (~4kB I think), 2kB for layout settings, then only have about 25kB of flash to work with. If you don't replace the 4kB bootloader with an external programmer you're stuck with even less.
• Latency and battery life will be a slightly worse.