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Simplify IoT connectivity of embedded devices

Posted: 24 Oct 2013 ?? ?Print Version ?Bookmark and Share

Keywords:Internet of Things? TCP/IP? operating system? microcontroller? Ethernet controller?

The system monitors this information throughout the day. If the resident is going to be home late from work, he or she can use HTTP to request that the micro send a web page with all of this information. The resident could then turn lights on in certain rooms, bump up the temperature, and perform other tasks by changing a few fields on the web page.

There are multiple ways to implement an Ethernet sub-system that matches each system's requirements.

Ethernet controller module: A controller module that includes a TCP/IP hardwired chip, transformer, and RJ45 can greatly simplify connectivity. A wide variety of modules are available off-the-shelf that provide fast time-to-market and attractive price points. This approach is ideal for engineers who want to develop an Internet-enabled system rapidly.

For example, developers can select modules like Wiznet's WIZ550io, W5100 shield, and Rabbit Semiconductor's Ethernet Modules RCM6760 MiniCore. With the growing popularity of the Arduino platform, the market is also starting to see many modules compatible with official Arduino boards.

TCP/IP IC plus an MCU: Designers can also attach a TCP/IP controller to their embedded microcontroller. For example, Microchip's ENC28J60 Ethernet Module can be directly connected to most microcontrollers with a SPI interface. These modules typically have a stand-alone Ethernet Controller IC with a host of features to handle most of the network protocol requirements. Infrastructure like this enables designers to build and share their own Ethernet projects. For example, there is a project on Github that enables Internet connectivity between Programmable System-on-Chip (PSoC) controllers and a device based on the ENC28J60. The same project that is based on PSoC 3 can be ported to PSoC 5 as well. The advantage of such an implementation is that it frees up the microcontroller core and other on-chip resources for other system functions. At the hardware level, we need only an RJ45 connector, magnetics, a 25MHz crystal or oscillator, and a few passive components.

Single-chip microcontroller with lwIP: Lightweight IP (lwIP) is a widely used, open source TCP/IP stack designed for embedded systems, and is maintained by a worldwide network of developers. For many applications, lwIP can deliver Ethernet functionality while significantly reducing resource utilisation of the MCU. Both MAC and PHY are physically required in the MCU to implement the stack.

lwIP is ideal for designers who are seeking an economical approach to connectivity. However, as it takes more of a DIY type of implementation, developers must also be willing to put in the effort to figure out the stacks. The challenges with this kind of implementation are system resource usage and the capability to dynamically assign MAC addresses. The dynamically re-configurable nature of a PSoC makes it possible.

The digital side of PSoC is composed of Universal Digital Blocks (UDB) that balance configuration granularity and efficient implementation. A cornerstone of this approach is to provide the ability to customise the device's digital operation to match application requirements. For example, the DMA on chip makes it possible to design configurable a RX & TX FIFO. The PSoC design environment allows developers to build their own Ethernet Component and use it as a virtual chip in the system-level design.

Conclusion
Connectivity is the future, and the world is being driven by the Internet to facilitate and expand communications. With silicon vendors offering more mature products with greater implementation options and flexibility, designers have the choice of purchasing at the level they need, from ready turnkey modules to DIY embedded approaches.

About the author
Meng He graduated from Marquette University with a Master of Science degree in Electrical Engineering and has been working at Cypress Semiconductor as a product manager since 2007.

To download the PDF version of this article, click here.


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