In-Home Display

Block Diagram

Design Considerations

With the on-going deployment of smart electrical meters (Automatic Meter Infrastructure) a two way communication back and forth from the utility to the consumer will be established. New sources of information will be available to the consumers, either directly through the smart electrical meter or through some form of energy gateway. This information can be utilized and put brought to the consumer in an informative way: an In Home Display (IHD).

An In Home Display allows utility customers to track their energy usage in chart or graph form based upon kilowatt hour used. It provides most types of energy awareness information that a customer may require: total energy consumption, real-time pricing, comparative analysis with typical energy usage and more.

An IHD is essentially a display, portable or in a wall (for new homes), that can communicate with utility meters (electric, gas, water) and others communication enabled in-home appliances (using ZigBee, Wireless MBus for instance). When ZigBee enabled, it can be set up to act as a coordinator or router. Thanks to these communication features, it can receive custom real-time messages from the utility companies regarding billing, energy prices and more.

The typical wireless communications are ZigBee (802.15.4 2.4GHz, typical in the US) or Wireless MBus (sub 1-GHz, more Europe approach). Depending of the system topology, the communication can be enabled by System On Chip (MCU and transceiver) or can be composed or one MCU running the different profile stack connected to the radio transceiver. In both cases it involves hardware and software both available from Texas Instruments and TI developer network. WIFI can also be an option for high end IHD and is available today.

Function of the graphical and information options, several classes of IHD will be distinguished that will lead to different natural choices of embedded processors:

Cost-Optimized IHD- a micro-controller like the MSP430 will be typically used as the main processor: it an ideal combination of flash, processing power and low-power optimum for long lasting battery operated designs. Its integration level enables an easy interface with communication modules (using UART of SPI) or RF transceiver. Some members of the family can drive a Segment LCD, thanks to an on-chip LCD driver , and provide an on-chip analog to digital converter that can be used to implement a touch screen function if a display with integrated controller is not used. Additionally, numerous Input/Output can be programmed to implement push button options. For sub 1-GHz solution the integration level can further be optimized using the CC430, combining the MSP430 and sub 1-GHz transceiver in one single Low Power RF system on-chip with without LCD segment controller. For ultra-low stand-by current to maximize Li-Ion battery life, TI offers LDO linear regulators with stand-by currents as low as 0.5-uA.  For ultra-low input voltages TI offers buck-boost DC/DC regulators that are ideal for powering MCU's from batteries including 1 to 3-cell alkaline, NiCd, or NiMH. Providing power to the MCU from battery voltages as low as 0.7-V, along with high efficiency, these regulators enable extended use of the battery charge and increases the application run-time.

Mid-Level IHD- If more processing power is required and if developers are looking for more advanced graphical libraries, the TI Stellaris Cortex M3 micro-controller family is an alternative providing a lot of pin to pin memory options, interfaces options as well as encryption solutions. The family comes with an Embedded Graphical Library available through the Stellaris Ware Software Offer. Depending on system constraints such as cost sensitivity or need for highest efficiency; TI offers optimized products to power Stellaris MCU-based systems, including high-input voltage regulators capable of powering MCUs from standard 24-V DC lines often found inside homes for doorbells and security systems.

High-End IHD- To support more interactive options that display a need for Operating System like Linux, processing power and interfaces would lead to the choice of the ARM9 Sitara microprocessor, like the AM1808. This MPU offers a fully integrated LCD controller unit and provides numerous software libraries for implementation.  For power, these devices require regulated 1.2V core, 1.8V, and 3.3V voltages. In addition, sequenced power-supply architectures are becoming commonplace in high-performance DSP systems. USB interfaces may be found in higher-end displays mainly for charging purposes or to upload multimedia content. TI offers the complete array of cost-sensitive integrated power management solutions for these types of higher-power, multi-rail systems.