SDAA486 September   2026 CC1312R

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
    1. 1.1 Smart Meter EU Regulations
    2. 1.2 Rotary Metrology Designs
  5. 2Smart Flow Meters and Sub-Metering Devices
    1. 2.1 Heat Cost Allocator (Sub-Metering)
      1. 2.1.1 HCA Key Functions
        1. 2.1.1.1 IrDA Communication Port
        2. 2.1.1.2 Temperature Measurement (Two-Sensor Method)
        3. 2.1.1.3 Segment LCD Support
    2. 2.2 Retrofit Add-On Module for Mechanical Water Meters
      1. 2.2.1 Retrofit Add-On Module Key Functions
      2. 2.2.2 Rotary Flow Metrology Implementation
        1. 2.2.2.1 Optical and Magnetic Rotary Sensing
        2. 2.2.2.2 Inductive Rotary Sensing
      3. 2.2.3 IrDA Wake-Up Detection
    3. 2.3 Smart Rotary Water Meter
      1. 2.3.1 Water Meter Key Functions
      2. 2.3.2 Segment LCD with CapTouch Activation
      3. 2.3.3 Tamper Detection With TMAG5231
      4. 2.3.4 OMS Compliant wM-Bus Communication Sub-system
    4. 2.4 Thermal Meters (Heat / Cold)
      1. 2.4.1 Thermal Meter Key Functions
      2. 2.4.2 Analog Signal Chain for DTM
      3. 2.4.3 Remarkable, Fully Digital Design for DTM
        1. 2.4.3.1 I2C and SMBus-Compatible Digital Sensor for Thermal Meters
        2. 2.4.3.2 1-Wire Compatible Digital Sensor for Thermal Meters
    5. 2.5 Bluetooth Low Energy (BLE) in Flow Meters
    6. 2.6 Influence of CRA on Smart Flow Meters and Heat Cost Allocators
      1. 2.6.1 Achieving CRA Conformance Through Careful System Design
        1. 2.6.1.1 Tamper Detection as a Physical Security Argument
        2. 2.6.1.2 Secure Key Storage
        3. 2.6.1.3 Secure Boot
        4. 2.6.1.4 Authenticated wM-Bus Communication
        5. 2.6.1.5 Secure Firmware Update via Over-the-Air Download (OAD)
        6. 2.6.1.6 Security Event Logging
  6. 3Summary
  7. 4References

2.3.1 Water Meter Key Functions

The rotary smart water meter block diagram in Figure 2-10 shows multiple sub-systems, all controlled by the CRA capable CC1312R or CC1314R10 Wireless MCU running applications code and the Sub-1GHz wireless protocol (for example, OMS wM-Bus v4.2.1 or v5.0.1):

  1. IrDA half- or full-duplex port
  2. Sub-1GHz Radio (uni- or bi-directional) with external Balun/RF Filter and Antenna
  3. Segment LCD display (with a Button for LCD activation) controlled by SCE firmware
  4. Tamper detection (for example, HCA removal from Heater) with TMAG5231

On the left the two MCU approach for LCD always on is presented, here the MSPM0L2117 is used as LCD driver and also can handle the IrDA port and the Tamper detection functionality, offloading the CC1312R device.

If the segment LCD with GPIOs is used, then the second block diagram to the right applies, with CC1314R10 running all LCD control GPIOs in addition to the IrDA port and Magnetic Tampering functions. This design is suited for water meters where the LCD display is typically off and only gets enabled by the user with a Button.

Optionally, an external SPI Flash device (not drawn) can be added on the SPI bus and powered by TPS22919 Load switch to store historical log data or backup firmware image, in the rare case when on chip 1MB Flash size of CC1314R10 is not sufficient to meet the system requirements.

Another optional device is the transceiver SX1261 or SX1262 by SEMTECH, enabling the proprietary long range Sub-1GHz protocol LoRa WAN, which may be used in some markets. The LoRa WAN software stack runs on CC1314R10 device, which features 296KB of SRAM memory, enabling dual-stack support for wM-Bus and proprietary long range protocols. Both SX126x and the SPI Flash devices are BOM population options and can be simply left out, if not required, providing a flexible system design with a single PCB design which covers multiple configurations across different markets.

The reason for selecting CC1314R10 over CC1312R/R7 for the Water Meter is the higher number of GPIOs required, due to the Segment LCD function. The VQFN64 8mm × 8mm RSK package with 46 GPIOs ensures that there are sufficient GPIOs for the LCD control, as Water Meter displays typically have 80 to 120 segments. TIDA-011020 would use 30 GPIO pins to drive a 96 segment 4 MUX LCD display, for handling the metrology and tampering and the IrDA communication functions the other 16 GPIOs are a must have.

For power saving, the load switch TPS22919 with typical shutdown current ISD of 2nA is added, it enables power to the SX126x and the SPI Flash devices only when these functions are used; otherwise, they are powered off by the load switch. The TPS22919 can be also left populated, when neither proprietary long-range radio nor SPI Flash are required.