Helios64: Update Maskrom Instruction

AndroidTool_Release_v2.52.zip does not work with current maskrom/loader
and it also has to be configured first.

Attach latest local copy that has been configured and describe link to
Rockchip GitHub.

Helios64: Update Maskrom Instruction

- Added Linux instruction
- Link maskrom page from button page

docs/helios64/button.md

@@ -32,6 +32,6 @@ User can enter recovery mode by pressing this button during boot up (bootloader
 
 2. User can then use flash tools to write new OS image into eMMC flash. Refer to this [section](/helios64/install/emmc/#step-5-writing-an-os-image-to-internal-emmc).
 
-User can also enter into *maskrom* mode in order to use some of the Rockchip programming tools (e.g [rkdeveloptool](https://github.com/rockchip-linux/rkdeveloptool)). For this, you will need first to enable [Jumper 13](/helios64/jumper/#usb-consolerecovery-mode-p13). To enter *markrom* mode, press and hold Recovery Button during power-up until System Status LED blinks 2 times.
+User can also enter into *maskrom* mode in order to use some of the Rockchip programming tools (e.g [rkdeveloptool](https://github.com/rockchip-linux/rkdeveloptool)). For this, you will need first to enable [Jumper 13](/helios64/jumper/#usb-consolerecovery-mode-p13). To enter *markrom* mode, press and hold Recovery Button during power-up until System Status LED blinks 2 times. Refer to [Maskrom page](/helios64/maskrom/)
 
 Under Linux, this button behaves as user button and when pressed will emit **BTN_0** keycode (refer to [Linux Input Codes](https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/plain/include/uapi/linux/input-event-codes.h)). Therefore this button can also be used to trigger other actions than recovery.

docs/helios64/maskrom.md

@@ -23,31 +23,31 @@ This USB device has Vendor ID *0x2207* and Product ID *0x330c*.
 
 ### 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.zip* from [Rockchip GitHub](https://github.com/rockchip-linux/tools/tree/rk3399/windows).
+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**.
-
-!!! Info
-    At this time of writing, the filename is *DriverAssitant_v4.6.zip* and the extracted folder is *DriverAssitant_v4.6*
+Run *DriverInstall.exe* under the extracted folder and press *Install Driver*.
 
 #### AndroidTools
 
-Download and extract *AndroidTool_Release.zip* from [Rockchip GitHub](https://github.com/rockchip-linux/tools/tree/rk3399/windows).
-
-!!! Info
-    At this time of writing, the filename is *AndroidTool_Release_v2.52.zip*.
+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.
 
-!!! Note
-    You could also compile it from source by following instructions at [Rockchip Wiki](http://opensource.rock-chips.com/wiki_Rkdeveloptool).
+Copy *rk3399_loader_v1.24_RevNocRL.126.bin* to *rkbin-master* folder.
 
-## Using Maskrom
+!!! 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.
 
@@ -61,7 +61,7 @@ Extract the downloaded *rkbin-master.zip* file.
 
  or
 
-**4 b)** Press and hold Recovery button. Power on the system and release recovery button after System Status LED blink twice. 
+**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
 
@@ -94,7 +94,40 @@ Extract the downloaded *rkbin-master.zip* file.
 
 **6.** Remove jumper on P13, you should have USB Serial connected to your PC.
 
-**7.** Continue to setup the OS through Serial Console.
+**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