TIDUF98 October   2024

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 End Equipment
      1. 1.1.1 Electricity Meter
    2. 1.2 Key System Specifications
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Highlighted Products
      1. 2.2.1 ADS131M03
      2. 2.2.2 MSPM0L2228
      3. 2.2.3 THVD1400
      4. 2.2.4 ISO6731
      5. 2.2.5 DRV5032
    3. 2.3 Design Considerations
      1. 2.3.1 Design Hardware Implementation
        1. 2.3.1.1 Analog Inputs
          1. 2.3.1.1.1 Voltage Measurement Analog Front End
          2. 2.3.1.1.2 Current Measurement Analog Front End
      2. 2.3.2 Energy Metrology Software
        1. 2.3.2.1 Software Architecture
        2. 2.3.2.2 Setup
          1. 2.3.2.2.1 Clocking Scheme
          2. 2.3.2.2.2 SPI
          3. 2.3.2.2.3 UART Setup for GUI Communication
          4. 2.3.2.2.4 Real-Time Clock
          5. 2.3.2.2.5 LCD Controller
          6. 2.3.2.2.6 Direct Memory Access
    4. 2.4 Hardware, Software, Testing Requirements, and Test Results
      1. 2.4.1 Required Hardware and Software
        1. 2.4.1.1 Cautions and Warnings
        2. 2.4.1.2 Hardware
          1. 2.4.1.2.1 Connections to the Test Setup
          2. 2.4.1.2.2 Power Supply Options and Jumper Settings
        3. 2.4.1.3 Calibration
      2. 2.4.2 Testing and Results
        1. 2.4.2.1 Test Setup
          1. 2.4.2.1.1 Viewing Metrology Readings and Calibration
            1. 2.4.2.1.1.1 Viewing Results From LCD
            2. 2.4.2.1.1.2 Viewing Results From PC GUI
        2. 2.4.2.2 Electricity Meter Metrology Accuracy Testing
        3. 2.4.2.3 Electricity Meter Metrology Accuracy Results
  9. 3Design Files
    1. 3.1 Schematics
    2. 3.2 Bill of Materials
    3. 3.3 PCB Layout Recommendations
      1. 3.3.1 Layout Prints
    4. 3.4 Altium Project
    5. 3.5 Gerber Files
    6. 3.6 Assembly Drawings
  10. 4Related Documentation
    1. 4.1 Trademarks
  11. 5About the Authors

2.2.2 MSPM0L2228

MSPM0Lx22x microcontrollers (MCU) are part of MSP highly integrated, ultra-low-power 32-bit MSPM0 MCU family based on the Arm® Cortex®-M0+ 32-bit core platform, operating at up to 32MHz frequency. These MCU offer a blend of cost optimization and design flexibility for applications requiring 128KB to 256KB of flash memory in small packages (down to 4mm x 4mm) or high pin count packages (up to 80 pins). These devices include a VBAT backup island, a segmented LCD controller on MSPM0L2228, cybersecurity enablers, and high performance integrated analog, and provide excellent low power performance across the operating temperature range. Figure 2-3 shows a block diagram of this device.

TIDA-010940 MSPM0L2228 Functional Block Diagram Figure 2-3 MSPM0L2228 Functional Block Diagram

Up to 256KB of embedded flash program memory with built-in error correction code (ECC) and up to 32KB SRAM with ECC and parity protection is provided. The flash memory is organized into two main banks to support field firmware updates, with address swap support provided between the two main banks. An additional 32-byte backup memory is provided in the VBAT island, supplied by the VBAT pin and retained even when the main supply (VDD) is lost.

The VBAT island provides a fully independent auxiliary power domain (separate from the main supply) which supplies low frequency modules from an alternate supply such as a battery, supercapacitor, or alternate voltage level (1.62 to 3.6V). The VBAT island includes the low frequency clock system (LFOSC, LFXT), the real-time clock, the tamper detection and time-stamping logic, an independent watchdog timer, and a 32-byte backup memory. Up to five digital IOs are powered from the VBAT supply. A charging mode is provided to optionally trickle charge a supercapacitor on the VBAT pin from the primary (VDD) supply when VDD is greater than VBAT.

An ultra-low power segmented LCD controller supports driving LCD glass with up to 59 pins in a variety of mux and bias configurations, enabling use of low cost displays.

Flexible cybersecurity enablers can be used to support secure boot, secure in-field firmware updates, IP protection (execute-only memory), key storage, and more. Hardware acceleration is provided for a variety of AES symmetric cipher modes, as well as a TRNG entropy source. The cybersecurity architecture is Arm® PSA Level 1 certified.

The MSPM0L2228 MCU in this design retrieves voltage and current samples from the ADS131M03 device and calculates metrology parameters. In addition, the device also keeps track of time with the RTC module, drives the LCD on the board with the internal LCD driver module, and uses one of the UART interfaces to communicate to a PC GUI using the isolated RS-485 circuit of the board. The CRC module of the MSPM0+ MCU is used to accelerate the CRC16 calculations that are done to verify the integrity of the ADC data packet sent by the ADS131M03 device.