SLAAES9 March   2025 MSP430FR5043 , MSP430FR6005 , MSP430FR6007 , MSP430FR6043 , MSP430FR6045 , MSP430FR6047

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Flow Meter Measurement Theory
    1. 2.1 TOF Measurement Algorithm Implementation
      1. 2.1.1 AbsTOF Calculation Method – Lobe
      2. 2.1.2 AbsTOF Calculation Method – Hilbert Wide
      3. 2.1.3 dTOF Calculation Method - Cross-Correlation
        1. 2.1.3.1 Get a High-Precision dTOF Result
        2. 2.1.3.2 Optimization in Cross-Correlation Method
    2. 2.2 Differences between ADC Approach and TDC Approach
  6. 3MSP430 MCUs for USS Application
    1. 3.1 USS Module
    2. 3.2 Differences Between USS and USS_A Module
    3. 3.3 Software Implementation on MSP430 MCUs
  7. 4Hardware Design Flow
    1. 4.1 Schematics
      1. 4.1.1 Water Meter Schematic – MSP430FR6047 and MSP430FR6007
      2. 4.1.2 Water Meter Schematic – MSP430FR6043 and MSP430FR5043
      3. 4.1.3 Gas Meter Schematic – MSP430FR6043 and MSP430FR5043
    2. 4.2 PCB Layout Guide
  8. 5Software Design Guide
    1. 5.1 USS Demo Projects and Related Resources
    2. 5.2 Demo Project Instruction
      1. 5.2.1 Files in Demo Project
      2. 5.2.2 Properties Setting in Demo Project
  9. 6Summary
  10. 7References

4.1.1 Water Meter Schematic – MSP430FR6047 and MSP430FR6007

This is a highly integrated design using MSP USS MCUs for the water meter application. For more details, see the TIDM-1019.

There are only a few points which need to be highlighted.

  1. For the USSXT, TI recommends to choose the load capacitor value by using Equation 9.
    Equation 9. C c r y s t a l + C l o a d + C l a y o u t = 34 p F

    Since the ADC approach is used in the USSLib, the measurement accuracy is barely affected by the crystal oscillator accuracy. Therefore, use a resonator on EVM boards for demonstration with good performance. A resonator also consumes less current than a crystal. If users do not care about the current consumption and have a wide temperature range in the application, then users can consider to use a crystal to replace the resonator. Users need to modify the USS_HSPLL_INPUT_CLK_TYPE and USS_HSPLL_USSXTAL_SETTLING_USEC in the software.

  2. For the CHx_IN/OUT circuit, TI recommends to use 1% resistors and 1% NP0 capacitors for a better USS performance. Users can change the value of the resistor and capacitor if this helps to get a better performance on the meter. As a note, TI tested several combinations with different transducers and took the value with 200Ohm and 1000pF for the best performance.
  3. For the power supply, TI recommends to use a dedicate LDO or DCDC power supply for the MCU. A good load transient response performance is important for the ultrasonic application.
  4. For the USS GUI connection, TI recommends to keep the I2C connection port (COMM_SDA, COMM_SCL and COMM_IRQ) on the board at first. To debug issues with USS GUI at the evaluation stage is easy.