An Arduino Due and some simple electronics mounted on a daughter board (known in Arduino circles as a "shield") are used to capture data from an audio output of the device being tested and from a light sensor attached to its display.
The design here interfaces photodiodes directly to an analog input pin of the Arduino, and channels from line level audio signals to other analog input pins. This forms the light sensor and audio signal inputs.
There is a list of parts for building this in prototype board form. Here is an example of the circuit implemented on a shield prototyping kit (with no apologies for the poor quality soldering!):
There are some connection wires on the rear of the board that cannot be seen in this photo.
The connectors for attaching the light sensors (centre) and the 3.5mm audio jack sockets (left side) are labelled. Only the right-audio channel is used on the two audio inputs.
To do this, you need to install the free Arduino IDE Make sure you have version 1.6 or later for Arduino Due support.
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Open the
arduino_sampling_code.inoproject in the IDE -
Plug the Arduino Due in via a USB cable connected to the "Programming" port.
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From the menu in the IDE, make sure the correct board type and port are selected.
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Click the compile+upload icon.
Once the code is uploaded, it is stored in flash memory. It does not need to be uploaded again, even if the Arduino is unplugged and powered off.
When using the Arduino with the rest of the measuring system, it should be connected via the other USB port, labelled "native".
The main python timing measurement code will report an error if it is unable to find a correctly connected Arduino.