From v0.9.0.0 and later, our Android app contains a feature which visualizes the audio signal. This is nice for demonstrave purposes as it visualizes the sound recorded by your microphone, but can also be used for debugging your electronical circuits for free.
Debugging your circuits using the Audio Scope
The Audio Scope visualizes the output of the Analog-to-Digital converter, which is typically digitizing the microphone signal. However, if you plug a 3.5mm audio jack into your Android device, this ADC is digitizing whatever signal you put on this 3.5mm audio jack.
That's correct: if you attach the microphone wire of your 3.5mm audio jack to a pin on your circuit, the SmartScope app will now display the electrical signal on that pin!
The most important thing you need to keep into account, is that the signal you present to your phone/tablet should be really low -- typically around 200mV MAX. This can be achieved by make a simple voltage divider from 2 resistors in series. This site explains the concept for a laptop, but it's exactly the same for an Android device.
Keep in mind...
An audio scope is not a real SmartScope, and of course there are some shortcomings/drawbacks which are inherent to all audio scopes:
- All audio inputs are AC-coupled, so you have no DC-coupling option when using the AudioScope
- Voltages are not absolute, so you cannot measure voltages. You can, however, see the variations of your signals over time, which is typically what a scope is being used for
- Sampling rate is 44.1kHz, while a real SmartScope can sample at 10MHz (2000 times faster)
- The AudioScope has only 1 input