Communicating bi-directionally
by Andreas Schneider, Executive VP & Founder of EnOcean.
Until now, the sensor functionality of self-powered EnOcean technology needed complex, discrete electronics for its implementation. New Dolphin system architecture, based on a sophisticated, power saving ASIC, is not only a high performance platform for cross-vendor deployment of wireless sensors and actuators but for the first time, it enables bi-directional communication of self-powered wireless sensors.
For over six years, EnOcean has been supplying components for pioneering wireless sensor technology that harvest their energy from the immediate environment: a keystroke, a miniature solar cell or even the temperature difference between a radiator and a wall. Today, over 500,000 energyautonomous wireless sensors are in service. In the building automation sector alone, more than 10,000 buildings have been fitted with EnOcean technology.
The first generation of this technology had to be fabricated from numerous discrete components but an ASIC module incorporating the EnOcean technology was recently introduced that unites RF technology and flexibly programmable digital electronics in a single, ultra-compact, low cost unit. This means that only a handful of components, such as a quartz resonator, an antenna and the power supply, are required to implement a bidirectional wireless sensor.
The Dolphin ASIC can run on as little as 2.5V. With ultra-low power energy management, the Dolphin EO3000I module operates reliably at a supply between 2.5 and 4.5V. Heart of the 40pin SMT chip, which has a footprint of just 6x6x1mm, is an 8bit 8051 MCU, optimised in power consumption, with a clock rate of 16MHz, 32KB flash memory and 2KB ram.
Fourteen connection pins of the module are programmable as I/O ports and two further pins permit the detection of wakeup signals. Eight of the I/O port pins function primarily as either analogue or digital I/Os and each of these pins can be used as either a digital input or output. Alternatively, pins ADIO 0-4 can also be used as analogue inputs, for example, to detect measured values.
Analogue configuration
ADIO 4-7 can be configured as analogue outputs and to enable this, the ASIC is equipped with a/d converters with a resolution of up to 12bits and d/a converters with 8bits resolution. Four additional I/O ports are intended for uses such as a fast SPI communication interface, enabling individual programming of the ASIC. If desired, the last two digital I/Os can be connected to a real time 32,768kHz quartz clock, making the Dolphin chip suitable for building synchronous wireless sensor networks.
EO3000I also contains an RF transceiver with ASK modulation, which can be programmed for use at either 868.3MHz for Europe or 315MHz for the US, Canada and Asia. Utilising this function requires no additional components except for the connection of a balun antenna, a few capacitors and a 16MHz quartz resonator for the processor and for RF generation.
Extremely low power consumption
To enable particularly low power applications, the ASIC is equipped not only with 2kB of normal working memory but also 32bytes of special ram that requires just 5nA to retain data and provide intermediate storage of measured values in sleep mode. With the wake-up timer, the current consumption of the EO3000I in sleep mode is 80nA. If the ASIC is additionally operated with a quartz clock, flywheel sleep mode is also extraordinarily thrifty at 500nA consumption. The various operating modes are also optimised for minimum power consumption.
Consequently, energy autonomous deployment of bi-directional wireless sensors and actuators is now possible. For example, a bi-directional, self-powered room temperature sensor can be implemented that, after transmitting its telegram with the measured value, for example temperature and humidity, can receive a message for set point correction along with the current time, and all with minimal circuitry.
The Dolphin chip comes with an intuitive operating system complete with an application programming interface to enable maximum flexibility in developing cross-vendor wireless modules and system applications. All the various functions of the chip can be realised using C programming: in-depth microcontroller experience and study of register settings are no longer necessary. The API contains the protocol stack for EnOcean wireless transmission as well as the functions for controlling energy management, for time control and for accessing the two working memories.
EnOcean also provides a development environment for programming applications. DolphinStudio is for configuring the chip and contains the API, a C compiler with linker in the trial version, a programming device with USB interface and two evaluation boards that enable individual application testing using a wide assortment of jumpers, buffer capacitors, LEDs and pushbuttons.
New plug & play modules
The Dolphin ASIC is primarily intended for manufacturers of high volume products but EnOcean is currently working on a new solution for users with lower volumes. The first products scheduled for roll-out are the tiny, 22x19mm TCM 300 SMT capable plug & play module and the upright inserted TCM 310 at 36.5x19mm. Standby energy consumption of these modules is less than half that of the previous TCM 120 and in standard functionality, such a module can serve as a single or four channel switch or as a single channel dimmer. It can also be used as a repeater via a simple connection pin, and users can individually reprogram the firmware to meet individual needs.
For energy autonomous sensor applications EnOcean is also introducing its STM 300 module for bi-directional applications. Its dimensions are comparable to the TCM modules and it is equipped with firmware for ultra-low power management on the basis of threshold value detection and connection with a wakeup timer as standard.
(Source www.connectingindustry.com, 27.03.2009)