Plug hackrf in while holding the dfu button (closest to the ant. port). Release button.
Then run:
dfu-util --device 1fc9:000c --download hackrf_one_usb.dfu --reset
(firmware from hackrf releases)
Then run:
hackrf_spiflash -w portapack-h1_h2-mayhem.bin
(firmware from mayhem releases)
After unplug, plug back in and should come up with mayhem logo.