SWRA679 January   2021 CC3200 , CC3220R , CC3220S , CC3220SF , CC3230S , CC3230SF , CC3235S , CC3235SF

 

  1.   Trademarks
  2. 1Introduction
    1. 1.1 Basics of the SAR ADC Architecture
    2. 1.2 Introduction to the CC32XX ADC
      1. 1.2.1 Main Features
      2. 1.2.2 ADC Sampling Operation
      3. 1.2.3 ADC Additional Information
  3. 2ADC Application Examples
    1. 2.1 Battery Voltage Measurements
      1. 2.1.1 Important Considerations
        1. 2.1.1.1 Extra Current Draw
        2. 2.1.1.2 Droop Correction
        3. 2.1.1.3 Offset Adjustment
        4. 2.1.1.4 Least Squares Fit
        5. 2.1.1.5 Choosing the Capacitor (for droop correction)
        6. 2.1.1.6 First Measurement
        7. 2.1.1.7 Time Between Measurements
  4. 3AC Measurements
  5. 4Useful References
    1. 4.1 Smart Thermostat
    2. 4.2 Measuring Air Quality With the Winsen MP503 Analog Sensor
    3. 4.3 Touch Position Detection With HMI Through Resistive Touchscreen
  6. 5References

4.3 Touch Position Detection With HMI Through Resistive Touchscreen

For more information, see CC3220 SimpleLink™ Wireless MCU Based Thermostat+BLE Provisioning Reference Design.

The resistive touchscreen is composed of two conductive layers separated by a gap and an insulated layer below. The two top conductive plates are coated with conductive material that provides uniform resistance across the layer. When a voltage is applied to the layer, it produces a uniform linear gradient of voltage. When the screen is touched, the pressure from the touch forces the two conductive layers to come in contact. By applying different voltage to the two conducing planes, the point of touch can be determined.

The smart thermostat uses the GPIOs and 2 channels of the ADC to read the X and Y position of the touchscreen. Multiplexing of the pins for the measurement is dynamically done. The resistors on the board must be modified to match the supply voltage.