Dolphin Chip rescues dream of wireless sensors without energy

19 March 2009

The new Dolphin system architecture, based on a sophisticated, power-saving ASIC, enables bi-directional communication of selfpowered wireless sensors. Andreas Schneider discusses the development.

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 energy-autonomous wireless sensors are in service. In the building automation sector alone, more than 10,000 buildings have been fitted with EnOcean technology. Until now, the sensor functionality of self-powered EnOcean technology needed complex, discrete electronics for its implementation.

The first generation of this technology had to be fabricated from numerous discrete components, but an ASIC module incorporating 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 bi-directional wireless sensor.

Dolphin ASICs can run on as little as 2.5 V
Thanks to its low-power energy management, the Dolphin EO3000I module operates reliably at a supply voltage between 2.5 and 4.5 V. The heart of the 40-pin SMT chip, which has a footprint of just 6x6x1 mm, is an 8-bit 8051 microcontroller, optimised in power consumption, with a clock rate of 16 MHz, 32 kB flash memory and 2 kB RAM. 14 connection pins of the module are programmable as I/O ports and two further pins permit the detection of wake-up signals. Eight of the I/O port pins function primarily as either analogue or digital I/Os. Alternatively, pins ADIO 0-4 can also be used as analogue inputs, for example to detect measured values. ADIO 4-7 can be configured as analogue outputs. To enable this, the ASIC is equipped with ADCs with resolution of up to 12 bits and DACs with 8 bits 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 realtime quartz clock (32,768 kHz) – making the Dolphin chip suitable for building synchronous wireless sensor networks.

The EO3000I also contains an RF transceiver with ASK modulation, which can be programmed for use at either 868.3 MHz (Europe) or 315.0 MHz (US, Canada, Asia). Utilising this function requires no additional components except for the connection of a balun antenna, a few capacitors and a 16 MHz 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 2 kB of normal working memory but also 32 bytes of special RAM that requires just 5 nA 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 80 nA. If the ASIC is additionally operated with a quartz clock, “flywheel sleep mode” is also thrifty with 500 nA 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 the first time. For example, a bi-directional, self-powered room temperature sensor can be implemented that, after transmitting its telegram with the measured value (e.g. temperature and humidity), can receive a message for set point correction along with the current time, and all with minimal circuitry.

Simple to program
The Dolphin chip comes with an intuitive operating system complete with an Application Programming Interface (API) to enable maximum flexibility in developing cross-vendor wireless modules and system applications. All the various functions of the chip can be realised using a C program – 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 controlling and for accessing the two working memories.

EnOcean offers a development environment for programming applications. The DolphinStudio program for configuring the chip contains the API, a C compiler with linker (trial version), a programming device with USB interface and two evaluation boards that permit individual testing of your own applications using a wide assortment of jumpers, buffer capacitors, LEDs and push buttons.

New plug & play modules
The Dolphin ASIC is primarily intended for manufacturers of highvolume products but EnOcean is currently working on a new solution for users with lower volumes. The first products scheduled for rollout are the 22x19 mm TCM 300 SMT-capable plug & play module and the upright inserted TCM 310 (36.5x19 mm). The standby energy consumption of these modules is less than half that of their predecessor, TCM 120. In its standard functionality, such a module can serve as a 1- or 4-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 introducing the STM 300 module, which can also be used in bidirectional applications. Its dimensions are comparable to the TCM modules, and it is equipped with firmware for low-power management on the basis of threshold value detection and connection with a wakeup timer as standard.

ANDREAS SCHNEIDER is the Executive VP & Founder of EnOcean GmbH

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