Crash course: Embedded programming with Arduino

Try your hand at embedded programming with this project

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The Wave Shield requires assembly and there is a lot of soldering, so do that first. When it's all together it will plug in nicely on top of your Arduino board. Then you'll solder your speaker and sonar sensor to the Wave board; follow the Halloween Pumpkin howto to see where the wires go. Make their wires long enough to allow you to mount the speaker and sensor where you want them inside your own project.

Use the LED series/parallel array wizard to figure out your LED wiring, and then solder your wiring harness together. Make sure your positive and negative leads are in correct order. The Halloween Pumpkin page says to use a glue gun to fasten the LEDs in place, but I prefer to drill holes that hold them snugly because it's less messy and easy to make changes. Once they're in place, solder the leads to the appropriate analog inputs and ground on your Wave board, and again leave enough slack in your wiring so you can move and easily access the Arduino and Wave Shield.

The clever part about the Halloween Pumpkin project is it saves a lot of code-writing by using an analog input to capture the audio output, which creates a variable-strength signal, and using that to animate the LEDs. Solder analog input #1 to the R7 1.5k resistor on the Wave board.

Plug your SD card into a PC in the usual way, with a card reader or built-in slot, and transfer your audio files to it. They must be in 22KHz 16-bit mono or lesser quality WAV. Then plug the card into the Wave Shield. Now you're ready to connect your PC to the Arduino with a USB cable, fire up the Arduino software, edit your sketch, and load it into the Arduino. One of Arduino's advantages is the speed of iteration -- you can quickly make and test changes in your code. Figure 4 shows my Singing Holiday Snowman in action.

fig-4-lit-snowman.jpgSource: Carla Schroder
Figure 4: Singing holiday snowman lit up and singing

Arduino code

I'm using the Halloween Pumpkin sketch (an Arduino program is called a sketch) with some minor changes. The Arduino programming language is pretty much a slimmed-down C/C++. You will have to make some changes to this sketch, so look for my comments in the sketch which are enclosed in the standard C multi-line comment symbols, /* */. Single-line comments, which start with //, are the original comments from the original sketch author.

We covered a lot of ground in this Crash Course, and hopefully your project blinks and sings just the way you want. If something doesn't work right, and you can't figure it out, go back to the Arduino tutorials and review the basics, and the Arduino forums are a good source of help.

Additional references

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