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:

For LCD:

• 1. 4.3" (480x272)
• 2. 7" (800x480)
• 3. 10" (1024x600)
• 4. 15.6" (1366x768)

Important: initially the boards are calibrated for a specific display. If you re-write the image (no matter whether the SD card or the NAND memory) you would need to use a mouse to calibrate the display initially. It might be impossible to calibrate it via touching the display.

For HDMI:

• 0. 480i
• 1. 576i
• 2. 480p
• 3. 576p
• 4. 720p50
• 5. 720p60
• 6. 1080i50
• 7. 1080i60
• 8. 1080p24
• 9. 1080p50
• 10. 1080p60

For VGA (VGA connection requires additional hardware, you would need to make board modifications yourself):

• 0. 1680x1050
• 1. 1440x900
• 2. 1360x768
• 3. 1280x1024
• 4. 1024x768
• 5. 800x600
• 6. 640x480
• 7. 1920x1080
• 8. 1280x720

The default Debian SD card setup has video output set to HDMI 720p/60Hz.