Establish or clear a callback function to run on interrupt for a GPIO.
Establish or clear a callback function to run on interrupt for a GPIO.
#### Syntax
#### Syntax
`gpio.trig(pin, type [, callback])`
`gpio.trig(pin [, type [, callback]])`
#### Parameters
#### Parameters
-`pin`, see [GPIO Overview](#gpio-overview)
-`pin`, see [GPIO Overview](#gpio-overview)
-`type` trigger type, one of
-`type` trigger type, one of
-`gpio.INTR_DISABLE` or `nil` to disable interrupts on this pin (in which case `callback` is ignored and should be `nil` or omitted)
-`gpio.INTR_UP` for trigger on rising edge
-`gpio.INTR_UP` for trigger on rising edge
-`gpio.INTR_DOWN` for trigger on falling edge
-`gpio.INTR_DOWN` for trigger on falling edge
-`gpio.INTR_UP_DOWN` for trigger on both edges
-`gpio.INTR_UP_DOWN` for trigger on both edges
-`gpio.INTR_LOW` for trigger on low level
-`gpio.INTR_LOW` for trigger on low level
-`gpio.INTR_HIGH` for trigger on high level
-`gpio.INTR_HIGH` for trigger on high level
-`callback` optional function to be called when trigger fires, trigger is disabled when omitted. Parameters are:
-`callback` optional function to be called when trigger fires. If `nil` or omitted (and `type` is not `gpio.INTR_DISABLE`) then any previously-set callback will continue to be used. Parameters are: