https://www.youtube.com/watch?v=S1CYbK8GKv8

If you are interested in electronics or engineering, you’ll have noticed a host of useful-sounding apps to help you in your design and build work. There are calculators, design aids, and somewhat intriguingly, apps that claim to offer an entire instrument on your phone. A few of them are produced to support external third-party USB instrument peripherals, but most of them claim to offer the functionality using just the hardware within the phone. Why buy an expensive oscilloscope, spectrum analyzer, or signal generator, when you can simply download one for free?

Engineering-oriented apps follow this cycle of hope and disappointment. But there are occasional exceptions. Let’s tour some of the good and the bad together, shall we?

Here’s a 2-channel Oscilloscope for your Android phone. It uses a base module driven by a dsPIC for signal processing. From there, an LMX9838 Bluetooth module broadcasts the data to the phone so that the waveform can be displayed. [Yus] ported some Python code he had been using over to a set of Java and XML files in order to get it working on Android.

Android Bluetooth Oscilloscope
http://projectproto.blogspot.fi/2010/09/android-bluetooth-oscilloscope.html

It is hardly news that you can use your smart phone as a really crummy oscilloscope. You can even use it as an audio frequency signal generator. There are also plenty of projects that allow you to buffer signals going in and out of your phone to make these apps more useful and protect your phone’s circuitry to some degree. What caught our eye with [loboat’s] phone oscilloscope project was its construction.

The enclosure used was an old CD ROM drive (although we imagine any optical drive would have worked). These are dirt cheap and–if your workshop closet looks like ours–probably free. The resulting build wouldn’t win any beauty contests, but for a piece of homebrew test gear it looked pretty good and required minimal effort.

OscilloPhone: Use your Smartphone as an Oscilloscope / Signal Generator
http://www.instructables.com/id/OscilloPhone-Use-your-Smartphone-as-an-Oscilloscop/

The PWM signal in question is fed through a piezo speaker in parallel with a resistor. The output from the speaker is then sent to an FFT (fast fourier transform) app for Android devices, which produces a picture of a waveform. [schoolie] then opens the picture in MS Paint and uses the coordinates of the cursor and a little arithmetic to compute the period and the duty cycle.