How to edit prebuilt Android images

Introduction

The article discusses the steps to follow in order to connect a display to your OLinuXino-LIME board.

Before continuing, please note that there are two major scenarios, depending on the display version you have available. The newer generation of displays require just a cable to connect to, while older generation of displays require additional adapter of the pitch.

How to determine whether you have newer generation or older generation display?

The names of the newer displays follow the pattern LCD-OLinuXino-XXX or LCD-OLinuXino-XXXTS. New ones were made with the idea to be able to connect to every OLinuXino or SOM board via one single cable. They have three LCD connectors at the back - one with 0.1 inch pitch; and two with 0.05 inch pitch. The first connector is used to connect the display to boards with 0.1 inch LCD connector. There are two 0.05 inch step ones because of the different layouts of LIME and LIME2 boards.

When you have determined whether you have newer or older display refer to the respective sub-chapter in the hardware setup below.

Hardware setup

If you own a newer display

You would need a cable to connect to your board. LIME boards have a 0.05 inch step LCD connector so the proper cable is CABLE-40-40-10CM that also has 0.05 step. Product page of the cable CABLE-40-40-10CM

Skip to the software setup further below.

If you own an older display

The information in this chapter is suitable only for A10-OLinuXino-LIME and A20-OLinuXino-LIME. The customers with LIME2 board might follow the guide but instead of A10-OLinuXino-LIME-UEXT should use another adapter board specifically made for LIME2. The reason is that LIME2 LCD connector has a different layout compared to the previous LIME boards.

For the hardware connection would need two different cables and a small adapter board. The cables are called CABLE-40-40-10CM and CABLE-IDC40-15CM. The first one has different size connectors on each end – one of the ends has 0.05'' step connector – the other 0.1'' step connector. The second cable has same size connectors (both 0.1'' step). The adapter is A10-OLinuXino-LIME-UEXT.

The connection goes like this:

OLinuXino-LIME BOARD –> CABLE-40-40-10CM –> A10-OLinuXino-LIME-UEXT –> CABLE-IDC40-15CM –> DISPLAY

To connect the display you would need to place CABLE-40-40-10CM between the LIME board and the small connector of A10-OLinuXino-LIME-UEXT. Then you need to place CABLE-IDC40-15CM between the display and the big connector of A10-OLinuXino-LIME-UEXT.

Be careful when disconnecting the pieces – especially around the 0.05'' step connectors – attempting to pull the connector off the pins completely in one go, would probably result in bent pins or a broken connector. Try to lever the sides bit by bit with a suitable object.

We know that this is not the most convenient solution. We have improved the hardware design and future revisions of the displays would have a 0.05’’ connector at the back (while retaining the default 0.1'' one). This would mean that a single CABLE-40-40-10CM would be required (no adapter or second cable). Such displays would be probably available by the end of 2014.

Software setup

Once the hardware is ready-and-set we have to enable the video output configuration for our specific display.

The most important part is to use an official software distribution downloaded from the board’s wiki article. Then there are two major scenarios: using official Android or using official Debian Linux.

If you are using Android you would need to download a specific Android release from the wiki article that has support for your display. Currently there is a limited support under Android for NAND memory – typically, there are only two images with support for both HDMI + 7'' display and HDMI + 10'' display. The Android for microSD card can be modified easier but yet the ready images lack all video output options.

If you are using Debian Linux there is a ready script to execute. It lets you choose between a greater number of video output methods and resolutions. To be able to execute the script you would need some sort of connection to the board (either a default for the distribution display or HDMI monitor or serial debug cable or successful SSH connection). When you are logged in the board type:

  ./change_display* (* = press ‘tab’)

or

  ./change_display_aXX_lime.sh (XX processor of specific Lime board)

and press "Enter".

Then choose the resolution and the interface(LCD, HDMI). Note that the selection of a specific resolution is done by navigating with the arrow keys and pressing "space" button. Make sure the asterisk marks your selection properly.

The supported resolutions are:

How to edit the parameters in Android distributions

For almost any Olimex Allwinner board there are Android images provided. These are ready-to-use images with all the settings already configured. The images are generally two types: suitable for NAND memory boot of the boards; or suitable for a microSD card boot.

We often get asked to provide Android images with different set of settings or support for custom resolutions. Unfortunately, we are unable to compile Android images for every possible resolution and every possible Alwinner board.

The easiest approach is to edit an already existing image as explained below. The other method would be to create an Android image from scratch.

Note that the method for editing Android image suitable for NAND memory is completely different compared to the method for editing Android image suitable for microSD card.

The algorithm to edit the Android image for the NAND memory:

 1. Download the latest official Android image for NAND from the wiki article of your board.

 2. Download and extract the program used for editing the parameters of a ready image. The program is called DragonFace. It can be downloaded from here: https://github.com/OLIMEX/OLINUXINO/raw/master/SOFTWARE/dragonface/Dragonface_V2.1.2.zip

 3. Start the program from DragonFace.exe and let it update on first launch. 

 4. After the update is complete and the interface of the program is available click on the "Firmware" button and then load the *.img file that we got in point 1.

During the opening of the firmware additional processes might attempt to start. Windows user account control might prompt for your approval. Make sure that you allow those.

If you receive an error loading the image: ensure that the torrent program or any local or remote program or proccess that might interfere with the image had been closed and the link to the image had been terminated. If the image you are goind to edit is open by another program you will not be able to edit it via DragonFace - the error that usually gets displayed in such a case is: "DragonFace: Firmware does not support the tools to modify, make sure that the firmare version: OK".

 5. After the load is complete navigate to the "Advanced Settings" tab. In the tab select "System Configuration". This would open the configuration in simple text form in your default text editor.

 6. Now we can edit parameters. More information on what the parameters mean and what values they might have is found here: http://linux-sunxi.org/Fex_Guide 

For example, to enable FullHD video output at 60Hz we need to change screen0_output_type and screen0_output_mode as follows:

screen0_output_type = 3

screen0_output_mode = 10, for 60 Hz

Under screen0_xxx_xxx it should be the HDMI settings.

 7. After we are done we save the text file and close it. Then we click the button "Save" at the bottom of the DragonFace interface. A prompt windows would appear and would allow us to specify a save location and name for the edited image.

During the save operation of the firmware additional processes might attempt to start. Windows user account control might prompt for your approval. Make sure that you allow those.

 8. Voila we have an image with custom settings. We are ready to burn it to the NAND memory of the board.