SLAA494B May   2011  – September 2023 MSP430AFE221 , MSP430AFE222 , MSP430AFE223 , MSP430AFE231 , MSP430AFE232 , MSP430AFE233 , MSP430AFE251 , MSP430AFE252 , MSP430AFE253

 

  1.   1
  2.   Implementation of a Single-Phase Electronic Watt-Hour Meter Using the MSP430AFE2xx
  3. 1 Trademarks
  4. 2 Introduction
  5. 3 Block Diagram
  6. 4 Hardware Implementation
    1. 4.1 Power Supply
      1. 4.1.1 Resistor Capacitor (RC) Power Supply
      2. 4.1.2 Switching-Based Power Supply
    2. 4.2 Analog Inputs
      1. 4.2.1 Voltage Inputs
      2. 4.2.2 Current Inputs
  7. 5 Software Implementation
    1. 5.1 Peripherals Setup
      1. 5.1.1 SD24 Setup
    2. 5.2 Foreground Process
      1. 5.2.1 Formulas
        1. 5.2.1.1 Voltage and Current
        2. 5.2.1.2 Power and Energy
    3. 5.3 The Background Process
      1. 5.3.1 Voltage and Current Signals
      2. 5.3.2 Phase Compensation
      3. 5.3.3 Frequency Measurement and Cycle Tracking
      4. 5.3.4 LED Pulse Generation
    4. 5.4 Energy Meter Configuration
  8. 6 Energy Meter Demo
    1. 6.1 EVM Overview
      1. 6.1.1 Connections to the Test Setup or AC Voltages
      2. 6.1.2 Power Supply Options
    2. 6.2 Loading the Example Code
      1. 6.2.1 Opening the Project
  9. 7 Results
    1. 7.1 Viewing Results on PC
    2. 7.2 Viewing Results During Debug
  10. 8 Important Notes
  11. 9 Schematics
  12. 10References
  13. 11Revision History

5.2 Foreground Process

The foreground process includes the initial setup of the MSP430 hardware and software immediately after a device RESET. Figure 5-1 shows the flowchart for this process.

GUID-19409409-C130-4446-83BA-35F19DB314FB-low.gifFigure 5-1 Foreground Process

The initialization routines involves the setup of the analog-to-digital converter, Clock system, general-purpose input/output (GPIO) (port) pins, timer and the USART for UART functionality. A check is made if the main power is OFF and the device goes into LPM0. During normal operation, the background process notifies the foreground process through a status flag every time a frame of data is available for processing. This data frame consists of accumulation of energy for 1 second. This is equivalent to accumulation of 50 or 60 cycles of data samples synchronized to the incoming voltage signal. In addition, a sample counter keeps track of how many samples have been accumulated over the frame period. This count can vary as the software synchronizes with the incoming mains frequency. The data samples set consist of processed current, voltage, active and reactive energy. All values are accumulated in separate 48-bit registers to further process and obtain the RMS and mean values.