Lesson51tinyos教程.doc

Lesson 5.1 Sensing This lesson introduces sensor data acquisition in TinyOS. It demonstrates two sensor applications: a simple application called Sense that periodically takes sensor readings and displays the values on the LEDs. And a more sophisticated application called Oscilloscope where nodes periodically broadcast their sensor readings to a basestation node. Using the Mote-PC serial communication described in the previous lesson the basestation forwards the sensor readings to the PC, where they are visualized with a dedicated graphical user interface. Introduction Sensing is an integral part of sensor network applications. In TinyOS 1.x sensing was syntactically connected with analog-to-digital converters (ADCs): TinyOS 1.x applications such as Oscilloscope or Sense used the ADC and ADCControl interfaces to collect sensor data. When new platforms appeared with sensors that were read out via the serial interface, not only did additional interfaces like ADCError have to be introduced, but it became clear that equating a sensor with an ADC was not always the appropriate thing to do. Usually sensing involves two tasks: configuring a sensor (and/or the hardware module it is attached to, for example the ADC or SPI bus) and reading the sensor data. The first task is tricky, because a sensing application like, for example, Sense is meant to run on any TinyOS platform. How can Sense know the configuration details (like ADC input channel, the required reference voltage, etc.) of an attached sensor? It cant, because the configuration details of sensors will be different from platform to platform. Unless Sense knows about all sensors on all platforms it will be unable to perform the configuration task. However, the second task - reading the sensor data - can be solved so that the Sense application can collect sensor data even though it is agnostic to the platform it is running on. In TinyOS 2.0 platform independent sensing applications such as Oscilloscope, Sense or Radio