Download the Firmware 

Open the mayhem firmware release page: https://github.com/portapack-mayhem/mayhem-firmware/releases/tag/v2.1.0 Download the firmware zip, i.e., mayhem_v2.1.0_FIRMWARE.zip

Extract it and find the following files,

Install the Driver

Enter into the 'driver' folder, find 'dpinst.exe', double click it to run the driver installation program.

Flash the DFU Firmware 

If the LEDs of your hackrf is abnormal, you may need to flash the DFU firmware. If you need do this, you can use 'dfu_hackrf_one.bat' to do it.

To do this, you need to let the hackrf go into the DFU mode. Hold the DFU button on the top of the Hackrf when pluging the USB cable between the HackRF and your computer. There will be a single green LED (i.e., the 3v3 led), indicating the device is ready to be flashed.

Then, double click 'dfu_hackrf_one.bat'.

When you see this, please click any key, for example, you can just click 'Enter' key.

Now the LEDs of your HackRF looks like this, These four leds (i.e., USB, RF, 1V8 and 3V3) are on.

Flash the Mayhem Firmware

If you purchased hackrf separately, the firmware in hackrf defaults to the firmware used separately by hackrf. At this point, when you install HackRF and Portapack H4M together, after H4M is turned on, although the LED display of HackRF lights up, the screen of H4M is black. This is because the firmware in HackRF is incorrect. You need to update the Mayfem firmware to HackRF.

Double click 'flash_portapack_mayhem.bat'.

When you see this, please click any key, for example, you can just click 'Enter' key.

Now, the mayhem firmware flashing is done. You can install the portapack H4M on the HackRF.