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

3.3 Software Implementation on MSP430 MCUs

MSP430FR60xx and MSP430FR50xx MCUs performs the complete acquisition process using integrated an USS module in the device for signal conditioning. Below figure shows this acquisition process.

Calculation Process Figure 3-2 Calculation Process

At the beginning of the sequence, MCU sends a train of pulses to the first transducer. The signal is then received by the second transceiver, after propagation time T12. The difference in time between transmission and reception determines the upstream (UPS) TOF.

Then, MCU repeats the same process in the opposite direction during the downstream stage, resulting in the propagation time, T21, which represents the downstream (DNS) TOF.

The dTOF can be calculated as the difference between T12 and T21 using the correlation method. According to Section 2.1.3.2, the USS library uses the absTOF result for reference to give the integer cycle differences between the absTOF results. And uses the cross-correlation method to provide the decimal part of dTOF result. With this method, we get the dTOF result.

The flow rate result is calculated based on absTOF, dTOF, meter constant and offset correction value according to Section 2.