pxt-calliope/docs/reference/input/on-pin-pressed.md

# On Pin Pressed

Start an [event handler](/reference/event-handler) (part of the program 
that will run when something happens, like when a button is pressed). 
This handler works when you press pin `0`, `1`, or `2` together with `GND`.
When you are using this function in a web browser, click the pins on the screen instead of the ones
on the BBC micro:bit.

If you hold the `GND` pin with one hand and touch pin `0`, `1`, or `2` with the other,
a very small (safe) amount of electricity will flow through your body and back into
the micro:bit. This is called **completing a circuit**. It's like you're a big wire!

```sig
input.onPinPressed(TouchPin.P0, () => {
})
```

## ~hint

This function works best when the BBC micro:bit is using batteries for power,
instead of the USB cable.

## ~

### Example: pin pressed counter

This program counts how many times you press the `P0` pin. 
Every time you press the pin, the program shows the number of times on the screen.

```blocks
let count = 0
basic.showNumber(count, 100)
input.onPinPressed(TouchPin.P0, () => {
    count = count + 1
    basic.showNumber(count, 100)
})
```

### See also

[BBC micro:bit pins](/device/pins), [pin is pressed](/reference/input/pin-is-pressed), [analog read pin](/reference/pins/analog-read-pin), [analog write pin](/reference/pins/analog-write-pin), [digital read pin](/reference/pins/digital-read-pin), [digital write pin](/reference/pins/digital-write-pin)