====== Having a great fun with GPIO on Android ======

** You must install the C2 Android Marshmallow Ver2.8 image or higher to access the 40pin GPIO properly.**

This WiKi explains how to make an Android app which can access GPIO ports.\\

You need to install [[https://developer.android.com/studio/index.html|Google Android Studio]] on your host PC.\\  
And add [[https://developer.android.com/ndk/guides/index.html|NDK and tools]] first before starting below steps.\\
We tested following steps on Android Studio 2.3 and NDK R14.

===== Ubuntu/Linux =====

==== Configure NDK path for Android Studio ====
Add this line in your ~/.bashrc file after installing Android NDK.
<code>
export NDK_PATH=[YOUR ANDROID SDK LOCATION]/ndk-bundle
</code>
For example
<code>
export NDK_PATH=/home/codewalker/projects/android-sdks/ndk-bundle
</code>
You can find the Android SDK location on this menu (File -> Settings -> Appearance & Behavior -> System Settings -> Android SDK)\\
{{:en:screenshot_from_2017-05-18_11_15_43.png?nolink&800|}}

After editing the bashrc file, you have to login again or type "**source ~/.bashrc**" on the command line.

==== Download example code ====
Download C2-WiringPi NDK library and App source code Project from [[https://github.com/codewalkerster/example-wiringPi| github]].
<code>
$ sudo apt install git
$ git clone https://github.com/codewalkerster/example-wiringPi -b mater
</code>

==== Run Android Studio and open the downloaded project. ====
{{:en:screenshot_2017-05-18_10-33-55.png?nolink|}}

==== Build the project to make an apk package ====
Select **Build -> Make Project** menu.\\
You will see a couple of error messages and click following texts to complete the build process.\\
//**Install missing platform(s) and sync project**\\
**Install Build Tools 25.0.2 and sync project**// \\
And you will have an apk file to run it on your ODROID.

===== Windows =====

==== Set environment PATH to point NDK folder path ====

{{:en:advanced_system_setting.png?nolink|}}

{{:en:environment.png?nolink|}}

{{:en:ndk_path.png?nolink|}}

 Reboot Windows.

==== Install git client program ====

[[https://git-for-windows.github.io/]]

==== Clone project ====

{{:en:git.png?nolink&700|}}

https://github.com/codewalkerster/example-wiringPi

Select origin/master.

{{:en:branch.png?nolink|}}

==== Install NDK ====

Toos -> Android -> SDK Manager

{{:en:android_sdk.png?nolink$500|}}

{{:en:ndk_install.png?nolink&500|}}



===== Features of example project =====

==== ADC and GPIO output ====
Read ADC value and show the voltage level with 19 LEDs on GPIO output.\\
{{http://dn.odroid.com/homebackup/android_wiringPi_ADC.png?600|}}
{{youtube>zyfULOkj0Vw?medium}}


==== PWM ====
Basic PWM control example. You can choose the number of PWM outputs 1 or 2.\\
And control the frequency and duty ratio.\\
{{http://dn.odroid.com/homebackup/android_wiringPi_PWM.png?600|}}

=== Gmail Notifier example ===
This is fun and useful project using the PWM port. \\
When you watch video or play games, you might lose a notification of the important email or message. \\
The flag is moving by servo motor which is connected to a PWM pin on 40pin GPIO port. \\
https://github.com/codewalkerster/GMailNotifier

{{youtube>Vvq77w87RWQ?medium}}
==== I2C ====
An example code to access our [[http://www.hardkernel.com/main/products/prdt_info.php?g_code=G144533067183|Weather Board]] to measure the temperature, humidity, atmospheric pressure, altitude and visible/invisible light intensities via I2C 
interface.\\

{{:en:img_20170526_153143.jpg?600}}

{{:en:screenshot_2016-04-25-02-38-54.png?600|}}

==== UART ====
A demo software for Sending and Receiving characters via UART interface. \\
{{http://dn.odroid.com/homebackup/android_wiringPi_UART.png?600|}}

==== 1 Wire ====
A demo software to access 1-wire protocol interfaced DS18S20 temperature sensor.\\
{{http://dn.odroid.com/homebackup/android_wiringPi_1wire.png?600|}}

===== Kernel for i2c =====
Open File Manager app.

Edit /storage/internal/boot.ini like this. (near end of file).

Before edit.
<code>
movi read dtb 0 ${dtbaddr}
# load kernel from vat or boot partition.
movi read boot 0 ${loadaddr}
#fatload mmc 0:1 ${loadaddr} Image
booti ${loadaddr} - ${dtbaddr}
</code>

After edit.
<code>
movi read dtb 0 ${dtbaddr}
# load kernel from vat or boot partition.
#movi read boot 0 ${loadaddr}
fatload mmc 0:1 ${loadaddr} Image
booti ${loadaddr} - ${dtbaddr}
</code>

Load kernel image from vfat partition built i2c.

If you could not find 'fatload' command, remove /storage/internal/boot.ini file and reboot system.