In my Smart Home user interface, I want to provide rotary dial controls for lighting and temperature control. How can I detect the user input from an on-screen rotary dial and use it in y application?

EVE has an innovative tagging and tracking feature which makes implementing touch controls easy, including rotary controls. Touch tagging allows you to assign a tag to an object on the screen. You can easily determine which item is being touched by reading the REG_TOUCH_TAG register, either by polling or in response to an interrupt (EVE can generate an interrupt on a change of touch condition)

Tracking extends this feature further via CMD_TRACK. You can set an area on the screen and then determine the relative position of the users touch within that area by simply reading REG_TRACKER. Tracking can support linear and radial modes.

  • The linear mode is ideal for sliders and scroll bars, and reports the distance along your defined tracked area from 0 to 65536
  • The radial mode is ideal for rotary dials. The tracking value represents the angle of the touch point relative to the object’s centre in units of 1/65536 of a circle. 0 means that the angle is straight down, 0x4000 is left, 0x8000 is up, and 0xc000 is right.

Tagging and Tracking support multi-touch (up to 5 touches) on capacitive touch versions of EVE such as the BT817, with five Tag and 5 Tracker registers (e.g. REG_TRACKER to REG_TRACKER_4) providing the results.