pub fn enable_interrupt(&mut self, threshold: u16) {
        self.pin.set_threshold(threshold, Internal);
        internal_enable_interrupt(self.pin.touch_nr(Internal))
    }
Enables the touch_pad interrupt.

The raised interrupt is actually
[`RTC_CORE`](crate::peripherals::Interrupt::RTC_CORE). A handler can
be installed with [`Rtc::set_interrupt_handler()`][1].

[1]: ../rtc_cntl/struct.Rtc.html#method.set_interrupt_handler

## Parameters:
- `threshold`: The threshold above/below which the pin is considered
touched. Above/below depends on the configuration of `touch` in
[`new`](Self::new) (defaults to below).

## Example
esp-hal/src/touch.rs