Raspbian

While working on another project, I set up my Raspberry Pi (revision B) with Raspbian. Although it was a bit time consuming, it was not difficult at all. Instead of using the default desktop environment (LXDE),  I decided to try out Raspian Mate as it’s a fork of the well-loved GNOME 2 desktop environment.

Raspbian

I was happy to see that GNOME 2 was still alive and well. I used to run Ubuntu on my home computers, but abandoned it when they switched over to GNOME 3 and Unity. The lack of features in GNOME 3, the clunky Unity interface and the poor device support in Ubuntu pushed me over the edge. I sold out to Macintosh and happily resigned myself to never having to look at xorg.conf ever again.

Raspberry Pi

It surprises me how far computers have come already in my lifetime. As a little girl, I remember playing with my grandfather’s Color Computer 2. It seemed remarkable at the time and I never expected computing to progress as rapidly as it has. For some perspective, the CoCo2 cost $240 in 1983 and had 16KB of RAM and an 8 bit processor at 1 MHz. Twenty years later, the Raspberry Pi costs $35 and has 512 MB of RAM and a 32 bit processor at 700 MHz. It will be interesting to see what the next twenty years brings.

Microcontrollers!

IMG_6193

Looking through some of my electronics stuff, I realized that I ten different kinds of microcontrollers! That’s not bad at all, considering that I only discovered my love of them last summer. There are five flavors of Arduino: Uno, Uno Ethernet, MEGA, MEGA ADK and Due. There are three flavors of Teensy: Teensy 2.0, Teensy++ 2.0 and Teensy 3.0. There are also two wearables: Lilypad Arduino and Adafruit Flora. So many microcontrollers, so little time!

Motion-Sensitive Paper Lantern

Back in February, I made a motion-sensitive lantern for the Lunar New Year. The idea was simple: have a lantern that appeared to be mostly plain but would reveal a design when a person moved closer to it.

Lantern from far away

The easiest form to use was a round paper lantern. I started with a 14″ white paper lantern and some markers. I then attempted to draw some snakes on it, as 2013 is the year of the snake. As I am not an artist, let’s pretend that these squiggles look like snakes.

Lantern up close

The next part was to add some lighting. The lighting needed to change color. I decided to go with LED strips from Adafruit, as I could wrap them in the center of the lantern and have fairly uniform lighting. I had some left over pieces from a previous project and this seemed like the perfect occasion to use them.

Next, the lighting needed to respond to motion. There were a couple of sensors that would have allowed me to detect motion, but I decided on a passive infrared (PIR) sensor. Interestingly, these sensors work by detecting rapid changes in infrared radiation (including those given off by body heat).

PIR Sensor

The code for this was very straightforward. The PIR sensor sends a high signal on its output pin whenever motion is detected. Therefore, it’s as simple as polling the output pin with digitalRead() and transitioning the lights based on changes in the output pin state.

Finally, I had to find a lightweight power source. I found an Energizer power pack, which was the perfect power supply for Teensy. It even came with a mini USB adapter, which meant that I could plug it directly into the Teensy without having to solder anything. Here is the final internal assembly of the lamp!

The final assembly

And here is the lamp, fully assembled and running!

Dance Dance Revolution Keyboard

Over the weekend, I turned a Dance Dance Revolution dance pad into a keyboard input device. The pad will be used as part of a larger project at the NYC Resistor 2013 Interactive Show. Here is how I did it.

The pad itself is one of those metal arcade style Dance Dance Revolution pads. The only output was a 15 pin D-Sub connector, much like a VGA cable.

Dance Pad

The dance pad connector

Fortunately for me, a fellow Resistor already went through the arduous task of figuring out the pinout for this particular pad. A little further research based on the pinout revealed that this particular model was a TX-1000. The full pinout can be found here.

The next task was to wire the connector to a microcontroller and try to read input from the board. I decided to go with a Teensy as it already has a library that supports keyboard output. In order to have the Teensy be recognized as a HID by a computer, you have to change the USB type. This can be done by changing Tools -> USB Type to “Keyboard + Mouse + Joystick”.

Now I needed to write some code to read the input from the dance pad and convert it to keyboard output. First, I had to define the input pins in the setup function of the Teensy code. This was done with pinMode using pullup resistors.

pinMode(leftPin, INPUT_PULLUP);   // Left arrow

The next step was to read the input from the control pad and send the corresponding keyboard character when a pad was pressed. Fortunately, Teensy offers a Bounce library which makes debouncing switches easy. First you declare a Bounce object on your input pin.

Bounce leftButton = Bounce(leftPin, 400);

Next, poll the pin in the loop() method for state changes. Once a state change is detected, send the corresponding keyboard key.

if (leftButton.update()) {
    if (leftButton.fallingEdge()) {
         Keyboard.set_key1(KEY_LEFT);
    }
}

Once everything was wired up and the Teensy code was running, everything seemed to work… except the right arrow. Unfortunately, this meant that it was time to take the pad apart!

Underneath a panel

The wires

After a bit of investigating and a few false starts, I found that the wires were easily accessible under the up arrow. Thankfully, the wires for each button were a different color so it was easy to determine which wires to test. Testing with a multimeter showed that the right signal wire in the cable was not working. After running a new signal wire for the right pad (and soldering everything else I cut), everything worked as expected! I then used a solderable D-Sub connector and enclosure from RadioShack to make a connector for the pad.

The completed connector

I could then hook the dance pad connector to my homemade connector and then a mini USB to USB cable from the Teensy to my computer. There is nothing more satisfying than navigating your computer by dancing!