As I got my Arduino, I had to dust out my electronics knowledge that I got back when I was at college. Arduino really makes it easy, even for the non electronics geek, to get into electronics really quickly.

My First Real Arduino Experiment

After a quick refresh into the world of electronics, I wanted to do a little experiment that would allow me to interface my newly bought Nexus S phone with Arduino. Since I didn’t connect my bluesmirf bluetooth module yet, I had to interface with Arduino using serial connection. There’s one problem though, I didn’t want to connect a “mobile device” with wires to a board.

The solution was simple:

1. Connect the Arduino board to a host computer
2. Run a TCP server on the host computer, that waits for commands from a client
3. The TCP server translates those commands, and sends them to the Arduino’s serial port

Circuit Design

The components setup is easy, you would control the 10 LED graph bar, as individual LEDs with current limiting resistors. Looking at the datasheet for the LED graph bar, it says that I would need 20mA of current to operate the LEDs. Unfortunately, I don’t have lower resistors than my 330Ω, so I used 10 330Ω resistors to provide around 15mA to each LED, which was enough.

LED Graph Bar Arduino Sketch

Arduino comes with a powerful language called the Arduino programming language, which is based on C/C++. So I had no problem understanding the language quickly, and start interacting with the board.

I connected the LEDs to ports 2 to 11 on the Arduino board, and sat them to output either HIGH (5v) to light on, or LOW (0v) to light off. Also in the setup function, I initiate the serial communication with baud rate = 9600.

As the loop function starts, I wait for serial bytes to arrive, as the bytes arrive, they arrive in ASCII encoded stream. I had to do a little conversion from ASCII to integer, and if the integer is between 0 and 9, I light the LEDs that correspond to that number plus 1, So if I receive 3, I would light 4 LEDs. I count from 0, because I wanted to keep my communication under 1 byte, plus that’s how machines count.

TCP To Serial Communication Server

To let the Nexus S communicate wirelessly with Arduino, I had to write something that would allow me to send serial commands from the mobile phone to Arduino. So I wrote a simple TCP server in Python. The Python server would receive the desired commands over WiFi, and translates those commands to Arduino using the serial port. I wouldn’t have used this server, if I connected the bluetooth module, since I can send those commands directly from Android phone to Arduino.

The TCP server is simple, I use the awesome library pySerial to open the serial port on my Arduino, with the same baud rate as defined on the sketch. If the connection has been established, I loop indefinitely waiting for commands, which in our case would be digits from 0 to 9. As I receive the digits, I convert them to ASCII, and send them to Arduino. If the letter ‘Q’ was received, the communication ends.

The Android App

The TCP server waits for commands to be sent from any device that it connects to, I had the server running on port 50000 of the same machine that is connected to the Arduino. and all I had to do is send the numbers of LEDs that I want to light. Using the accelerometer sensor on the Nexus S, it was really easy. I just had to filter out the jitter, as the accelerometer sensor is very sensitive, so I could send normal integers over the air to light how many LEDs I want.

The full source code of the app is available under GNU GPLv3 license on my github repository, please feel free to use it.

Resources

• Arduino website
• Sparkfun
• Arduino Playground
• Arduino-Python 4-Axis Servo Control

If you don’t know me that well, I have been an active web developer, who develops and writes mainly in Arabic, on a blog called Almashroo.

Web development has been my passion for the past 10 years, and I couldn’t imagine a day, where I don’t write a JavaScript line here, and PHP line there, complementing them with some (X)HTML and CSS.

Entering The Mobile World

Today, I’m moving on to a more interesting and challenging area of development, that is, mobile software development. I’ve spent the past few months developing an open source cross platform mobile app, as a first project, to officially get into this small, and yet challenging world.

I can’t wait to tell you all about, as I’m currently preparing the official web site that hosts it, stay tuned for more information that will come shortly.

What About the Web Development?

Well, I’m first and foremost a web developer, who still enjoys it. However, I think the knowledge that I’m getting currently from the mobile, will in fact benefit me greatly as web developer.

Will I return to the web development soon? The short answer, probably yes, but it will take a me a while to get back.

I have redesigned and developed my web site from the grounds up, using the new, and exciting features of HTML5 and CSS3. I used CodeIgniter as a framework, for the main site, along with Markdown to control the conent, and WordPress for this blog. For the people who knew my website before, I have converted it to English, so I can communicate my thoughts to the rest of world.

I have also collected some of my open source projects, and put them on Github, so you can see and fork them as you like.

What is this Mobile App I am Working On?

As I said previously, it’s an open source cross platform mobile app, that will benefit my country’s users a lot, this app will be supported on multiple platforms, iPhone, BlackBerry, Android, and any mobile that can run Java ME apps.

A blog post announcing it will be posted right here soon, and when I say soon, I mean in the next few days. So stay tuned.