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Texas Instruments Smart Meter Board


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Overview of the ZigBee Smart Energy capabilities of the TI Smart Meter Board and In-home Display Reference Designs. From Smart Grid Electronics Forum, San Jose, CA, October 2010

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Texas Instruments Smart Meter Board

  1. 1. TI Smart Meter Board Zin Thein KyawTexas Instruments- Metering BU Smart Grid Electronics Forum October 18-20, 2010 San Jose, CA
  2. 2. Agenda• Introduction• ZigBee Smart Energy 101• Example SE HAN Network• Anatomy of the Smart Meter Board• Anatomy of the In-Home Display• Exchanging messages between host processor and ZigBee module• Conclusion
  3. 3. Introduction• Texas Instruments “smart meter board” showcases embedded processing, metrology, and communication modules for NAN (neighborhood) and HAN (home area) networks• Measures a real load on the mains connection and communicate the reading to any in home display using ZigBee• The ZigBee module uses the ZigBee Smart Energy profile for over-the-air application level messaging• Examine use cases for ZigBee Smart Energy as a communications protocol in the home area network with some ZigBee Smart Energy 101• Discuss how to tunnel application level messages between the host processor and the ZigBee module to achieve communication between the smart meter and the in-home display
  4. 4. ZigBee Smart Energy 101• ZigBee Smart Energy is a ZigBee Alliance public application profile that defines commands and attributes for the following device types: – Energy Service Portal (ESP) – The ESP is the device that acts as a gateway into the home and manages the ZigBee Smart Energy HAN – In-Premise Display (IPD) – The IPD is a device that presents energy consumption data and price information to the end user either by text or graphical means – Metering Device – These are typically metering devices such as gas, water, and heat meters
  5. 5. ZigBee Smart Energy 101 (cont.)• Programmable Communicating Thermostat (PCT) – Device used to control the cooling and heating systems of the home• Load Control Device – A device such as a pool pump or water heater that is capable of receiving demand response and load control events from the utility head end• Smart Appliance – Like a load control device, a smart appliance could be a washer, dryer, oven that is capable of receiving demand response or pricing events from the utility head end• Range Extender – A range extender has no other purpose than to be a router device for other devices in the HAN
  6. 6. ZigBee Smart Energy 101 (cont.)• A cluster is a ZigBee term for a collection of commands and attributes specific to a particular behavior• In ZigBee Smart Energy, the following clusters are supported: – Price – Provides functionality to convey price information from the utility head end – Demand Response and Load Control (DRLC) - Provides functionality for devices such as thermostats and other devices that perform load control – Simple Metering - Provides functionality to retrieve usage data from electric, gas, water metering devices
  7. 7. ZigBee Smart Energy 101 (cont.)• Message – Provides functionality to deliver text messages• Time – Provides functionality to synchronize time between the time server (ESP) and other devices. UTC is used as the common time base• Key Establishment – Provides functionality for establishing a link key for secure application level communication between pairs of devices
  8. 8. Example SE HAN Network In  remise  isplay  hows  onsumption,  rice  ignals P D s c p s and  ext messages  rom  SP t f E • All communication with the ESP (e-meter) is secured at the In‐Premise  Display  (IPD) application layer with the link ESP Sends PCT L oad Control Event to c ontrol HVAC key established via Certificate Based Key Establishment Programmable Communicating (CBKE) Thermostat  (PCT) • AES-128 block cipher is used to Smart  ppliances  hows  rice,  ext A s p messages  rom  SP f E t encrypt packets, the key is the established link key   ESP  (E‐Meter) Smart  Appliance Simple  etering  evice  eports  urrent M D R C Summation  elivered  ttribute  eriodically D A P Simple  Metering  Device (Gas, Water, Heat)
  9. 9. Anatomy of the Smart Meter Board• To provide real time metering updates to the ZigBee module, the applications processor can use either UART or SPI• A device such as a ZigBee Smart Energy in-home display (IHD) can query the smart meter board for metering data such as instantaneous demand• This information is delivered to the in-home display as the InstantaneousDemand attribute (defined within the ZigBee Smart Energy Profile’s simple metering cluster)
  10. 10. Anatomy of the In-Home Display• IHD reference design based on the MSP430F4619 and the CC2530 ZigBee SoC (System- on-Chip)• The ZigBee Smart Energy firmware inside the CC2530 is queries the smart meter board for the instantaneous demand and output the values to the MSP430 application processor via UART• The MSP430 displays the instantaneous demand value on the LCD
  11. 11. System Block Diagram Smart Meter Board Read Attribute Request for In‐Home Display Instantaneous Demand ZB Read Attribute Response for ZB MSP430 Instantaneous Demand MSP430 LCD LCD LOAD• Shows system level interaction between the Smart Meter Board and the In-Home Display using the ZigBee Smart Energy Profile• The IHD performs a read attribute request to query for the instantaneous demand attribute, receives the value in the read attribute response, then tunnels the data to the MSP430 which displays it on the LCD• The protocol used by the host processor to facilitate this transaction is discussed next
  12. 12. Exchanging messages between host processorand ZigBee module• The TI Z-Stack provides a transport layer to allow a host processor to exchange application data with the application inside the ZigBee module• This transport layer is called the “Z-stack Monitor and Test API”, or “MT” for short• The protocol format discussed here assumes UART communications, although SPI can be supported as well with some minor differences to the protocol format (i.e. SOF and FCS bytes are not required for SPI mode)
  13. 13. Exchanging messages between host processorand ZigBee module (cont.)• SOF (Start of Frame): This is a one byte field with value equal to 0xFE that defines the start of each general serial packet• MT CMD (Monitor Test Command): This contains 1 byte for the length of the actual data, 2 bytes for the MT command Id, and the data ranging from 0-250 bytes• FCS (Frame Check Sequence): This is a one byte field that is used to ensure packet integrity. This field is computed as an XOR of all the bytes in the message starting with LEN field and through the last byte of data. The receiver XORs all the received data bytes as indicated above and then XORs the received FCS field. If the sum is not equal to zero, the received packet is in error
  14. 14. Exchanging messages between host processorand ZigBee module (cont.)• To tunnel messages into the Z-Stack /**************************************************************** * @fn esp_ProcessAppMsg application, the host processor uses the * APP_MSG MT command * @brief Process MT SYS APP MSG to retrieve link key * * @param msg - pointer to message * * @return none */ static void esp_ProcessAppMsg( uint8 *msg ) {• The host processor application can create switch (msg[6]) { its own payload format within the case SET_INST_DEMAND: // set attribute data for instantaneous highlighted “Message” field that has an demand espInstantaneousDemand = BUILD_UINT24(msg[7], msg[8], associated “MsgLen” msg[9]);• In this example, the Z-Stack application break; case USER_DEFINED_CMD: sees a ‘SET_INST_DEMAND’ in the first // do something byte of the “Message” payload to mean } break; that this is a set of the local } InstantaneousDemand attribute• The MSP430 sends this command every couple of seconds to update this attribute in the ZigBee module• The ZigBee module on the IHD asynchronously queries for this attribute over the air using a “read attribute request”
  15. 15. Exchanging messages between host processorand ZigBee module (cont.)• The ZigBee module on the IHD shuttles the payload data to the MSP430 for display using the DEBUG_MSG MT command• The DEBUG_MSG MT command is a very convenient way to tunnel application messages received over the ZigBee network back to the host processor• In this example, the response to the read attribute request containing the instantaneous demand metering data is sent via UART using the DEBUG_MSG packet format• The Z-stack application can call the following API function at any time to tunnel application payload messages to the host processor: – MT_BuildAndSendZToolResponse(((uint8)MT_RPC_CMD_AREQ | (uint8)MT_RPC_SYS_DBG), MT_DEBUG_MSG, METER_DATA_LEN, meterData);
  16. 16. Conclusion• Provided an overview of the ZigBee Smart Energy application profile and examined use cases in the HAN• Discussed the system level interactions between the smart meter board and in-home display to provide current consumption data to the user• Discussed how to use the Z-Stack MT Interface, which provides an easy way to tunnel messages to and from a host processor
  17. 17. References• ZigBee Smart Energy Profile Specification, 075356r15ZB_AMI_PTG-AMI_Profile Specification.pdf, ZigBee Alliance• ZigBee Specification, 053474r17ZB_TSC-ZigBee- Specification.pdf, ZigBee Alliance• Z-Stack Smart Energy Developer’s Guide, SWRA216, Texas Instruments• Z-Stack Monitor and Test API, SWRA198, Texas Instruments