Maskrom is special internal firmware of RK3399 that run **Rockusb** driver automatically when there is no 
bootable firmware found on on-board storage such as SPI flash, eMMC or microSD card.

On Helios64, there are two ways to enter the maskrom mode:

- Disable SPI flash and eMMC according to [Boot Mode Jumper](/helios64/jumper/#boot-mode-p10-p11) and remove microSD card.

- Using [Recovery Button](/helios64/button/#recovery-button)

Rockusb is a vendor specific USB class from Rockchip to download firmware. 
This USB device has Vendor ID *0x2207* and Product ID *0x330c*.

!!! Info
    U-Boot has *rockusb* command, but it is not compatible with the Rockchip utilities

## Prerequisites

### RK3399 loader

  In maskrom mode, SoC initiliazed without DRAM and storage support therefore it need *loader* to initialized DRAM and prepare the flashing environment.
  
  Download the loader from [here](/helios64/files/maskrom/rk3399_loader_v1.24_RevNocRL.126.bin)

### Windows

!!! Info
    Latest version of the tools can be downloaded from [Rockchip GitHub](https://github.com/rockchip-linux/tools/tree/master/windows).

#### Rockusb driver

Download and extract *DriverAssistant_v4.91.zip* from [here](/helios64/files/maskrom/DriverAssitant_v4.91.zip).

Run *DriverInstall.exe* under the extracted folder and press *Install Driver*.

#### AndroidTools

Download and extract *AndroidTool_Release_v2.71.zip* from [here](/helios64/files/maskrom/AndroidTool_Release_v2.71.zip).

### Linux

Download prebuilt rkdevelop from [Rockchip GitHub](https://github.com/rockchip-linux/rkbin/archive/master.zip). 
Extract the downloaded *rkbin-master.zip* file.

Copy *rk3399_loader_v1.24_RevNocRL.126.bin* to *rkbin-master* folder.

!!! Note
    - You could also compile it from source by following instructions at [Rockchip Wiki](http://opensource.rock-chips.com/wiki_Rkdeveloptool).
    - Prebuilt binaries are tested on Ubuntu 18.04 and 20.04

## Write OS Image to eMMC Using Maskrom

**1)** Make sure the system is powered off.

**2)** Put jumper cap to P13 to enable it.

![!Jumper P13](/helios64/img/maskrom/jumper_p13_enabled.jpg)

**3)** Plug in USB type-C cable to Helios64 and the other side to PC.

**4 a)** Disable SPI flash and eMMC according to [Boot Mode Jumper](/helios64/jumper/#boot-mode-p10-p11) and remove microSD card. Power on the system.

 or

**4 b)** Press and hold Recovery button. Power on the system and release recovery button after [System Activity LED](/helios64/front-panel/#helios64-enclosure) blink twice. 

### Under Windows

**1.** Open Device Manager and verify whether rockusb device is recognized.

![rockusb on Device Manager](/helios64/img/maskrom/rockusb_device.png)

**2.** Run **AndroidTool.exe** and check whether there is **Found One MASKROM Device**.

![!AndroidTool Main Window](/helios64/img/maskrom/androidtools_00_main.png)

**3.** Press button to load and select following files,

- Loader = rk3399_loader_v1.24_RevNocRL.126.bin

- Image = OS image to write

!!! Warning
    The image must be Raw image, not in compressed form.

![!AndroidTool Files loaded](/helios64/img/maskrom/androidtools_01_ready_to_download.png)

**4.** Checklist both row and press **Run** button. Observer the log textbox.

![!AndroidTool Writing Images](/helios64/img/maskrom/androidtools_02_download_in_progress.png)

**5.** The log textbox will show **Download image OK** when finished and system will automatically reboot.

![!AndroidTool Writing Images](/helios64/img/maskrom/androidtools_03_done.png)

**6.** Remove jumper on P13, you should have USB Serial connected to your PC.

**7.** Continue to [setup the OS through Serial Console](/helios64/install/first-start/).

### Under Linux

**1.** Verify whether rockusb device is recognized.

```
lsusb -d 2207:330c
```

It should return something like,

`Bus 001 Device 014: ID 2207:330c Fuzhou Rockchip Electronics Company RK3399 in Mask ROM mode`

**2.** Open terminal under rkbin-master folder.

**3.** Send loader to Helios64

`sudo tools/rkdeveloptool db rk3399_loader_v1.24_RevNocRL.126.bin`

**4.** Write OS image to eMMC

`sudo tools/rkdeveloptool wl 0 /path/to/os_image.img`

!!! Warning
    The image must be Raw image, not in compressed form.

**5.** After image writing finished, reset the system

`sudo tools/rkdeveloptool rd`

**6.** Remove jumper on P13, you should have USB Serial connected to your PC.

**7.** Continue to [setup the OS through Serial Console](/helios64/install/first-start/).


## References

[Rkdeveloptool - Rockchip Open Source Document](http://opensource.rock-chips.com/wiki_Rkdeveloptool)

[Rockusb - Rockchip Open Source Document](http://opensource.rock-chips.com/wiki_Rockusb)