TIDUE90 July   2018

 

  1.    Description
  2.    Resources
  3.    Features
  4.    Applications
  5.    Design Images
  6. 1System Description
    1. 1.1 Key System Specifications
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 Classification of Scenarios With Liquid Present
      2. 2.2.2 Liquid Influence on Capacitive Touch Sensing
      3. 2.2.3 Self Capacitance and Mutual Capacitance
        1. 2.2.3.1 Self Capacitance
        2. 2.2.3.2 Mutual Capacitance
      4. 2.2.4 Other Considerations
    3. 2.3 Highlighted Products
      1. 2.3.1 MSP430FR2633
    4. 2.4 System Design Theory
      1. 2.4.1 Shield Sensor Electrodes
      2. 2.4.2 Mutual Capacitance Shielding
      3. 2.4.3 Design for Noise Immunity
      4. 2.4.4 Power Supply Grounding Effect
  8. 3Hardware, Software, Test Requirements, and Test Results
    1. 3.1 Required Hardware and Software
      1. 3.1.1 Hardware
      2. 3.1.2 Software
    2. 3.2 Test and Results
      1. 3.2.1 Liquid Test With Well Grounded Power Supply
        1. 3.2.1.1 Continuous Water Flow Test
        2. 3.2.1.2 Continuous Water Spray Test
      2. 3.2.2 Conductive Noise Immunity Test
      3. 3.2.3 Liquid Test With Battery-Powered Supply
        1. 3.2.3.1 Continuous Water Flow Test
        2. 3.2.3.2 Continuous Water Spray Test
      4. 3.2.4 Third Party Test Report
  9. 4Design Files
    1. 4.1 Schematics
    2. 4.2 Bill of Materials
    3. 4.3 PCB Layout Recommendations
      1. 4.3.1 Layout Prints
    4. 4.4 Altium Project
    5. 4.5 Gerber Files
    6. 4.6 Assembly Drawings
  10. 5Software Files
  11. 6Related Documentation
    1. 6.1 Trademarks
  12. 7About the Author

3.1.1 Hardware

The hardware used in this reference design include the TIDM-1021 PCB (see Figure 12), an MSP430 CapTIvate MCU programmer board (CAPTIVATE-PGMR) (see Figure 13), and a CapTIvate communications isolation board (CAPTIVATE-ISO) (see Figure 14).

The programer board is used to program the MSP430FR2633 MCU on the TIDM-1021 PCB and also to provide the communication to the CapTIvate Design Center GUI for tunning the sensors and collecting the measurement data. The communication isolation board is used to maintain UART communication when TIDM-1021 PCB is powered from an external power source. This is mainly for test data collection purposes and, if the system is powered from the host PC, there is no need for the CAPTIVATE-ISO board.

The TIDM-1021 PCB includes:

  • 12 mutual capacitance buttons
  • 12 LEDs for touch indication feedback
  • An audio buzzer for touch indication feedback
  • An MSP430FR2633 MCU
  • A 20-pin connector to CapTIvate MCU programmer board

Section 3.2 lists other hardware used to test this reference design in different cases.

TIDM-1021 tidm-1021-hardware-pcb-front-(left)-and-back-(right)-photograph.pngFigure 12. TIDM-1021 Hardware PCB Front (Left) and Back (Right)
TIDM-1021 tidm-1021-msp430-captivate-mcu-programmer-board-(captivate-pgmr)-photograph.gifFigure 13. MSP430 CapTIvate MCU Programmer Board (CAPTIVATE-PGMR)
TIDM-1021 tidm-1021-captivate-communications-isolation-board-(captivate-iso)-photograph.gifFigure 14. CapTIvate Communications Isolation Board (CAPTIVATE-ISO)