Samsung Android smartphones like the A8 have a small menu on board which cannot be opened via the Android interface.
This is probably why it is often called a secret menu.
But it's rather a service menu that has to be opened via a special code. The following is a summary of how to open the service menu on the Samsung Galaxy A8, for example to read the sensor data:
1. To do this, open the phone app on the Samsung Galaxy A8 and the keypad in it.
2. Enter the following code to display the Samsung Service Menu: *#0*#
You will now see several tiles on the screen of your Samsung Galaxy A8.
Each tile represents a functional test. It is especially interesting if you take a closer look at the tile "Sensor".
Here the sensor data of the Samsung Galaxy A8 are output in real time.
You now know the Samsung service menu and how to open it.