TIDUFH8 November   2026

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Terminology
    2. 1.2 Key System Specifications
  8. 2System Overview
    1. 2.1 Key Devices
      1. 2.1.1 CC1312R7
      2. 2.1.2 MSPM0L2117
      3. 2.1.3 TPS27081A
      4. 2.1.4 TMAG5231
    2. 2.2 System Architecture
      1. 2.2.1 Rotary Metrology Sensing and Wireless Communication
        1. 2.2.1.1 LC-Sensing
        2. 2.2.1.2 Optical Sensing
        3. 2.2.1.3 Magnetic Sensing
      2. 2.2.2 LCD Display, Tamper Detection, and IrDA Communication
      3. 2.2.3 Multi-Protocol Radio Sub-System
      4. 2.2.4 Interfaces Between M0L2117 and CC1312R7
      5. 2.2.5 Additional Features
      6. 2.2.6 Future Proven Solution for EU Cyber Resilience Act (CRA)
  9. 3Design and Documentation Support
    1. 3.1 Design Files
      1. 3.1.1 Schematics
      2. 3.1.2 BOM
      3. 3.1.3 PCB Layout Recommendations
        1. 3.1.3.1 Layout Prints
        2. 3.1.3.2 Gerber Files
        3. 3.1.3.3 Assembly Drawings
        4. 3.1.3.4 Altium project
    2. 3.2 Tools and Software
      1. 3.2.1 System Architecture Overview
      2. 3.2.2 Tools
    3. 3.3 Documentation Support
    4. 3.4 Support Resources
    5.     Trademarks
  10. 4About the Author

2.2.2 LCD Display, Tamper Detection, and IrDA Communication

The LCD display is a key metrological function of any water meter and is typically implemented as always on, meaning LCD is visible to the user 24/7. To achieve this with only a few uA power consumption on average, a dedicated HW module for LCD support is required, which is provided by the MSPM0L2117 device. Reducing the average LCD power consumption even by 1uA is a significant step, as it directly impacts the battery lifetime of the water meter.

Typically, water meter LCD displays use multiple segments in 4-MUX mode, with a total number of segments ranging from 64 to 160 segments. As shown in Table 2-1 the exact power consumption depends upon the number of segments being active (or visible to the user), here the LCD refresh rate is not altered. Updating the refresh rate also has a significant impact on both contrast and power consumption, hence system designers optimize the refresh rate by reducing it to the minimum value, which delivers acceptable LCD contrast over the full voltage supply range for the water meter.

Table 2-1 shows a test application using 93 segment LCD and running on LP-MSPM0L2117 LaunchPad™, with the following configuration: MSP in STANDBY1, T1 TIMER (2sec periodic) wakeup, LCD MODE 5 with charge pump.

Table 2-1 Total Power Consumption for MSPM0L2117 and LCD Display

LCD display (see LP-MSPM0L2117)

#Active segments

 Power Consumption [uA]
0 (none) 2.3
42 2.9
93 5.3

Often, LCD displays have multiple views and can switch from one view to the next based on timer or user interaction, such as pressing a button. Power consumption change depending on the selected view and Table 2-1 summarizes the values, measured depending on the number of active segments. The schematic with MSPM0L2117 schematic portion uses the same LCD device and the same 64-pin MCU as on LP-MSPM0L2117, making code development with the LPAD easy.

The GDH-1638WP display (see LCD specification in Chapter 2.7 Liquid Crystal Display (LCD)) needs 30 pins total (4 COM and 26 SEG lines), and due to its dimensions MCU placement and routing under the LCD is possible.

TIDA-011019 MSPM0L2117 With LCD Display, TMAG5231 and IrDA LED Port Figure 2-6 MSPM0L2117 With LCD Display, TMAG5231 and IrDA LED Port

Both SEG25 and SEG26 lines were added to support LCD displays with up to 2 × 15 pins with 2.54mm pitch on the PCB, enabling maximum of 104 segments in 4 × 26 configuration.

One differentiated feature of MSPM0L2117 is the software configurability of each LCD pin as either COM or SEG line, which allows customers to use any segmented LCD display. If the footprint of the custom PCB is not fitting "as is", then a simple PCB adapter board can be designed. This PCB adapter can be mounted on a stand-off receptacle using the drill holes for GDH-1638WP display pins and can adjust the pinout as required.