Integrated sensor nodes with GSM modems simplify the task of wireless data acquisition: Page 4 of 5

January 11, 2012 // By Ajay Bharadwaj and Balaji Mamidala
A sensor network typically consists of a number of sensor nodes which each acquire signals from a sensor or multiple sensors and a system to transmit and process the data acquired from sensors. The sensor nodes can communicate the data within one another or to a centralized location over a wired or wireless network.
collected and processed from a single location anywhere in the world. Users can dynamically configure each and every modem remotely based on data sent across from the network. In certain networks, a single node would have GSM capability. Other nodes would send their data to this particular node to be transmitted to the centralized server. This could reduce the cost of the overall system but would not be possible if nodes are not clustered together. GSM modems also have the ability to provide instant alerts using SMS (short messaging service) or by transmitting data to a different, high-priority IP address based on certain conditions. These features can be used for fault tolerance and redundancy checks.

Let us consider an example of a GSM modem (SIM300) where communication happens over a serial port with the microcontroller. The modem has a standard set of commands called AT commands. These commands control the operation of the modem from the microcontroller. The microcontroller sends these commands over a UART (Universal Asynchronous Receive Transmit) interface at a specified baud rate. The data sent through the serial port can be transmitted to a centralized server by configuring the modem using a specific set of commands. Thus, interfacing with the GSM modem simplifies data acquisition and processing in sensor networks.

Complete system implementation

A sensor node consists of an analog signal chain and also requires a host of digital peripheral interfaces. Also each sensor node may be interfaced to different kinds of sensors, requiring flexibility in its interfaces and I/Os. Programmability of individual nodes plays a critical role in a successful implementation of a sensor network.

Figure 3: Simplified implementation of a sensor node using PSoC.

Figure 4: An implementation of a sensor node using PSoC. Click image to enlarge.

Mixed-signal programmable microcontrollers like PSoC from Cypress provide analog and digital subsystems which can be configured to provide the functionality required by individual nodes. This eliminates the

Design category: 

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