About half a year ago I programmed a small app for Android that communicates with an Arduino over Bluetooth (http://coretechrobotics.blogspot.com/2013/12/controlling-arduino-with-android-device.html). It had some very basic features and a simple user interface, which was just enough for the project it was designed for. But no two projects are alike.
Because of
that I decided to make a universal remote that would be customizable to all
possible applications.
Ideas
The main
idea is that the user should be able to create his own remote, without having
to learn java programming. This would require the app to have some kind of
built in editor.
Another
part is Multitouch, which is essential for any touchscreen application. It
seems to be simple at first but as I knew from my previous attempt at an
android app, this makes things extremely complicated. Imagine you don’t just
have an X/Y position of your mouse pointer but a whole array of those.
Implementation
Instead of
finally learning how to program in pure Java I went with Processing again. This
helped me a lot and reduced the time I had to spend on the project.
At first I
needed Multitouch. This was a difficult part, I had to read through a lot of
Android documentation and Internet articles until it finally worked. Maybe I
will write a separate Post about this in the near future.
The next
step were proper UI elements like sliders and buttons. My previous app used the
controlP5 library by Andreas Schlegel (http://www.sojamo.de/libraries/controlP5/).
But I wanted something of my own. I chose to write a UI library from scratch,
with a simple edgy design and full Multitouch integration. The four UI elements
are sliders, joysticks (2D-Sliders), buttons and switches.
The editor is
the main part of the app, from there the user can drag and drop the elements on
the screen.
The color can be
selected in a popup window with RGB sliders.
Another
important thing: If you look at a RC remote for a car, the steering wheel
centers itself with a built in spring. This way the car will drive straight if
you let go of the wheel. The same applies to the sticks of an airplane remote.
For this purpose I made a second window that lets you select which slider or
which axis of a joysticks should jump back to the middle position.
Saving
those UI layouts is also implemented. This means you can create up to 8 layouts
and save or load them. The most recent layout will be loaded automatically with
the app’s startup.
Finally,
with a press of the back-button on your Android device the editor buttons vanish
and you can use the controls you created.
This means that the slider values and button
states are transmitted over Bluetooth. Actually I wanted to write the Bluetooth
part myself but had to give up after a while. The process of selecting the
Arduino from a menu is complicated enough. To save development time I am using
the Ketai Bluetooth library again (https://code.google.com/p/ketai/).
Protocol
The protocol
is basically the same as in my previous app, with some additions to support switch
states and the slider centering. If a UI element changes, its key (a character
A-Z) will be transmitted, followed by its value. This way, the Arduino knows
what variable to write the value to. If no control is touched, nothing will be sent.
If multiple elements are being changed at the same time, all their values are being
transmitted, one at a time. This works fine for up to 3-4 touch points, but you
can cause some errors if your try to touch too many elements at the same time,
which is should be impractical anyway.
Installation Instructions
Unfortunately
I don’t have a Google Developer account, so you won’t find my app on the Play
Store. You can download the .apk-file from this link:
1. Download the .apk and transfer it to
your android device
2. Open it with a file explorer and
install it
3. Done! You can now create your own
Bluetooth Arduino remote
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT
WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO
THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
Example Arduino Sketch
I also
wrote a simple example sketch you can upload to an Arduino board of your
choice. It handles the serial communication with a Bluetooth board and writes
the values of the remote to variables.
This is not
a fully features library, so you will have to make some manual adjustments
depending on which UI elements are used in the Android app. But this is nothing
more than Copy and Paste.
Potential Improvements
I put a lot
of time into it, but the app still isn’t flawless. There is a settings-button, which
currently has no function because there are no changeable settings. The Bluetooth
protocol could use some reworking, too. But overall I am very pleased with the
outcome of this project.
