SLAA842B December   2018  – August 2019 DS90C401 , DS90C402 , MSP430FR2512 , MSP430FR2522 , MSP430FR2532 , MSP430FR2533 , MSP430FR2632 , MSP430FR2633 , MSP430FR2672 , MSP430FR2673 , MSP430FR2675 , MSP430FR2676

 

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9 Step 7: System Validation and Field Testing

The seventh step of designing a successful capacitive touch sensing system is to perform the system validation with the prototype units under all the expected operating condition. TI recommends building 20 to 50 units for field testing.

If the system meets performance requirements, the design can move to mass production. If the system does not meet performance requirements, you can either adjust the performance expectation or revisit the system design.

Table 16 is a system validation check list.

Table 16. System Validation Check List

No. Design For Test Recommendations
1 CapTIvate Design Center Communication Interface Place a UART or I2C communication interface on the board for connecting to CapTIvate Design Center. This can be removed on production units.
2 Function Testing Test the unit with all the functions enabled in the design.
3 EMC Testing Define the EMC testing standard and pass criteria.
4 Environment Drift Testing Define the environment drift testing standard and pass criteria.
5 Signal-to-Noise Ratio Margin Analysis Perform SNR measurement using CapTIvate Design Center with all of the noise sources enabled in the design.

Make sure Advice = GOOD

1. CapTIvate Design Center Communication Interface

  • It is much easier and more reliable to monitor the capacitive touch performance by using the CapTIvate Design Center real-time tuning feature.
  • It is highly recommended to leave a UART or I2C communication interface connection for CapTIvate Design Center on the prototype and field testing units. They can be disabled or removed on production units.

2. Function Testing

To ensure the reliability of the product, make sure to test the capacitive touch performance with other functions enabled in the design and also with switching other functions on and off. The other functions may include: LED driver, motor driver, wireless communication, near-field communication(NFC), battery power supply.

3. EMC Testing

  • Define the EMC testing standard and stress level as well as the pass criteria.
  • Example: Class A pass/fail criteria based on IEC 61000-4 standard for equipment under test (EUT)
    • The EUT must not exhibit any false touch detections during or after the test
    • The EUT must always detect valid touches during and after the test.
    • If the EUT contains slider or wheel sensors, the position must be reported accurately to within an acceptable limit during and after the test.
    • The EUT must not experience a processor reset during the test.

Refer to Noise-Tolerant Capacitive-Touch Human-Machine Interfaces Design Guide for complete details on EMC testing.

4. Temperature Drift Testing

  • Define the product operating temperature range, fastest expected change rate and the pass criteria.
  • Define the product operating humidity percentage range and pass criteria.

5. Signal-to-Noise Ratio Margin Analysis

Perform SNR Measurement using CapTIvate Design Center with all the noise sources enabled in the system and make sure you are getting the GOOD advice. Refer to Sensitivity, SNR, and Design Margin in Capacitive Touch Applications for details.