This git repository contains an Arduino sketch which is used to test the 8-Bit parallel in/serial out shift register IC 74HC165.
The specific use case and pinout has been intended for for testing the "splitflap classic controller" shield in combination with the magnetic switches (hall-effect sensors). In the code it is used in conjunction with an Arduino Leonardo - but it shouldn't be difficult to adapt for other Arduino platforms.
Holding magnets near the sensors should toggle the output from high to low (there are pull-up resistors, the switches connect to ground when closed):
