The Arduino Sketch (code) uses the external interrupt (int 0) on Arduino’s digital pin 2 (D2). This is used to read the output pulses coming from the water flow sensor. When Arduino detects the pulse, ...

Also, in the setup() you can see this line attachInterrupt(0, count, LOW); that is used to attach an interrupt on pin 2. In our case Arduino UNO has 2 external interrupts: on pin 2 with ID 0 and on ...

To prevent data corruption when using multiple SPI devices on the same bus, care must be taken to ensure that they are only accessed from within the main loop, or from the interrupt routine ...