I'm trying to use the /HWB pin to run my bootloader on an ATMmega32u4. I compiled the basic LUFA DFU Bootloader, using 0x7000 as the BOOT_START value, 32KB flash size and 4K boot size. I have the HWBE fuse set. I have the /HWB line pulled high with a 10K resistor, and a button connecting it to GND when pressed.
When I plug it in via USB, it works fine, my computer finds it even when I don't press the button to enable the bootloader. When I power it externally through an ISP header, it also runs the bootloader. The button has no effect. What could be happening?