SLAA877 December   2018 MSP430FR2633

 

  1.   Capacitive Touch Gesture Software and Tuning
    1.     Trademarks
    2. 1 Introduction
    3. 2 Gestures
      1. 2.1 Theory of Operation
      2. 2.2 Sensor Gesture Processing
      3. 2.3 Gesture Software Overview
        1. 2.3.1 Slider Gesture
        2. 2.3.2 Wheel Gesture
        3. 2.3.3 Button Gesture
        4. 2.3.4 Sensor Handlers
        5. 2.3.5 How to Add Gestures to the CapTIvate Framework
    4. 3 Tuning
      1. 3.1 CapTIvate Design Center
        1. 3.1.1 Enabling Gesture Sensor Output
        2. 3.1.2 CDC Plot Channel Assignments
      2. 3.2 Tuning Process
        1. 3.2.1 Tap
        2. 3.2.2 Double Tap
        3. 3.2.3 Swipe
        4. 3.2.4 Slide
    5. 4 Example Demonstration Software Installation
      1. 4.1 Project Directories
      2. 4.2 Import the Project Into CCS

2.1 Theory of Operation

To understand how gesture detection works, first look at how a gesture is detected. The MSP430FR2633 MCU with CapTIvate capacitive touch technology measures the change in capacitance on the CAPTIVATE-BSWP panel caused by a finger touch on a button, slider, or wheel sensor. The CapTIvate touch library includes fundamental algorithms that determine if a sensor is touched and the position of the finger on slider and wheel sensors.

The MSP430FR2633 has a dedicated 16-bit CapTIvate timer that generates a periodic capacitive touch measurement interrupt every 20 milliseconds, by default, and is user configurable in software. During each interrupt, the buttons, slider and wheel sensors are measured, followed by the gesture processing, which uses this periodic sampling rate as a time base measurement for finger touch and release events. Since the CapTIvate peripheral has it's own dedicated timer, no general-purpose 16-timers on the MCU are needed, leaving them available for the main application.

NOTE

Important Concept: Gesture timing is based on the sensor sampling rate.