lv_example

A template for Omega2 Dash programs using the LittleV Graphics Library

Out of the box it supports:

• All configuration (lv_conf.h and lv_drv_conf.h) required for:
  • The Linux Framebuffer - will draw to the Omega2 Dash display
  • The XPT7603 touch input device on the Omega2 Dash
• A small demo (provided by main.c)
• A script to cross compile the code for the Omega2 Dash (using Docker and the OpenWRT SDK)
• A makefile and instructions to build it as an OpenWRT package (see openwrt directory)

Using Docker to Compile for the Omega2 Dash

A quick and easy method for cross-compiling this code for the Omega2 Dash

It's possible to use the OpenWRT SDK in a Docker container to compile this code for the Omega2 Dash. The first time you do this might take a few minutes since image files will need to be downloaded. Afterwards, the compilation will be pretty quick.

Make sure you have Docker installed, then run:

sh compile.sh

This will use the OpenWRT SDK in a Docker container to compile the code in your local copy of this repo.

The output, a binary file and an ipk package will be in the bin directory.

Binary File

The binary file can be copied to the Omega2 and then executed. Say you copied it to /root on the Omega2, it can be executed by running /root/output.

IPK Package File

The ipk file is an OpenWRT software package. It can be copied to the Omega2 and used to install the lv_example package. Let's say it was copied to /tmp/lv_example_0.0.1-1_mipsel_24kc.ipk, it can be installed by running:

cd /tmp
opkg install lv_example_0.0.1-1_mipsel_24kc.ipk

The lv_example binary will be installed to /usr/bin. You can then execute it from anywhere just by running:

lv_example

All of the package details are defined in the OpenWRT Makefile, including the package name, installation directory, and more

Modifying the Template

Feel free to use this as a starting point for your own UI project on the Omega2 Dash. That's exactly what this repo is intended for!

Using Libraries

If you end up using additional libraries in your project, you'll need to make a few modifications in the OpenWRT Makefile in order to successfully compile the code using the compile.sh script.

All changes to be made in the openwrt/Makefile file:

1. Add the package name of the library to the dependencies of this package
2. Add the library to the linking flags used for compilation.

An Example

Let's say your UI project is based on the code in this repo and uses libugpio to toggle the GPIOs when buttons are pressed on the touchscreen.

In openwrt/Makefile, find the line that defines the DEPENDS for the package. Add a + and libugpio, the name of the package:

DEPENDS:=+libugpio

If your updated code has more than one dependency, it would look like this DEPENDS:=+libugpio +otherdependency

Then, find the line where TARGET_LDFLAGS, the linker flags to be used compilation. Add -l and the library name:

TARGET_LDFLAGS += -L$(STAGING_DIR)/usr/lib -lugpio

Changing the Package Name

If you build your own software package based on the template, it would make sense to change the package name.

To change the package name, find and replace the text lv_example with your given package name in the following files:

• Dockerfile
• openwrt/Makefile

Note that changing the install definition in the OpenWRT makefile will change where the binary will be installed on your Omega2 Dash device!

Learn more about OpenWRT package makefiles here: https://openwrt.org/docs/guide-developer/packages