Hi Jonathan,
The INT pin should follow the state of the interrupt from the capacitive touch panel when the BT81x is in sleep mode. If you scope the INT output from EVE and put EVE into the sleep mode, you should see low pulses each time you touch the screen.
In active mode, you can check the REG_INT_FLAGS to see which source caused the interrupt. Note that reading it will clear the flags and so when you see INT low the first read will give the flags.
The Interrupt operates similarly to most MCUs whereby you have the global INT bit (REG_INT_EN) to enable interrupts and then you have mask bits to determine which sources will generate an interrupt (REG_INT_MASK). Once the INT pin is asserted, your MCU should read REG_INT_FLAGS to see which source caused it. We have a table of interrupt sources in the BT815/6 datasheet in the Interrupts Section which you can use to see which bits correspond to which source
Some interrupts will occur periodically in normal operation (such as swap) whereas others will only be activated by a user action (such as TAG when the user touches the screen and the tag changes). However, you can set the mask bits such that only the sources you require will generate an interrupt. You may use the TAG or TOUCH interrupt for the application you mentioned where the interrupt occurs on a user touch.
Best Regards, BRT Community