Hi Lijo,
Flip flop is same as Bistable Multivibrator which very easy. It is a tricky question to misguide you.
A bistable can set or reset the output by external pulse, which means that you can store 1 bit digital data. That is same as a flip flop.
You can try this link for more details ...
please help me to interface hc-sr04 ultrasonic sensor with raspberry pi.
i think that the raspberry pi will get damaged if i connect directly to hc-sr04....
hc-sr04 is a 5v device while raspberry pi is a 3.3v device..