Friday, May 8, 2009
Ultra-Low-Power Wi-Fi Module Targets Industrial And Sensor Network Applications
When you think of wireless sensor networks for remote monitoring and control, you probably think of ZigBee, Bluetooth, Crossbow, or some proprietary ISM-based (industrial, scientific, medical) radios. While such networks work fine, there is always the issue of tying them to an enterprise local-area network (LAN) or the Internet, and that takes extra work. Now you can use Wi-Fi for such applications with minimal interfacing issues thanks to the Redpine Signals SenSiFi 802.11n wireless module (Fig. 1). It has all the features and benefits of a Wi-Fi transceiver but with features making it directly applicable to sensor applications. Also, it has the low power consumption to make it practical.
Designated the RS9119-N-11-31, the module is based on Redpine’s RS9110 system-on-a-chip (SoC), a complete Wi-Fi radio on-chip compatible with 802.11b/g/n standards in single-stream mode, not multiple-input multiple-output (MIMO). It also includes a built-in antenna, frequency reference, power management, firmware in flash, and a variety of interfaces (Fig. 2). The module can collect a full range of telemetry information including temperature, humidity, motion, light, pressure, location, and battery level through standard analog and digital sensor interfaces.
The microcontroller, an Atmel ATXMEGA64, implements a small, embedded operating system on which multiple applications can be built. The fully selfcontained module includes standardscompliant wireless LAN (WLAN) functionality with WPA2 security, a network stack that terminates TCP/IP and UDP connections with IPv6 capability, and configuration capability through UART or wireless. Interfaces include UART, SPI, I2C, JTAG, and GPIO. A 10-bit analogto- digital converter (ADC) is provided for sensor data conversion. The module is available in a 31- by 44-mm quad flat no-lead (QFN) package.
The SenSiFi is built for extremely low power consumption of 2.4 to 3.6 V using system-level and profile-driven finegrained power control, a microcontroller with an ultra-low-power mode working off a low-frequency clock source, and a WLAN subsystem with multiple power modes. With a single 3-V, 2000-mAh battery and uploading sensor data every two minutes over an IPv6 framework, it can achieve more than three years of battery life. Its high-performance WLAN subsystem further enhances range and effectiveness of data transfer while saving energy.
The module is available for evaluation through a fully implemented evaluation board that integrates temperature, humidity, and pressure sensors, an accelerometer, battery management, fullfunctional firmware for WLAN protocol and device control, a configuration utility, and a Web-based tracking application that provides a graphical representation of sensor data. Redpine also provides sample sensor management functions on the microcontroller, along with application programming interfaces (APIs) for applications development. The module is sampling now.
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