Whatever kind of electronic application you are developing, designing, or just thinking in your mind, it is expected that it has or will have in the next future a wireless feature. The capacity to communicate with other devices without a wired connection allows saving money, makes the installation much easier, and, why not, is very fashionable.

So, which kinds of wireless protocols are available today for the electronic designers? Well, the ZigBee protocol is probably the most popular and widespread solution for industrial applications, small terminals, and also home and building automation.

The ZigBee protocol is based on the IEEE 802.15.4 wireless personal area network (WPAN) specification and is explicitly targeted for device connectivity. It was defined at the end of 2004, and is controlled by the ZigBee Alliance which now includes over 200 companies. The purpose of ZigBee is to provide a protocol for network connection of small devices, and to provide a wireless remote monitoring capability. ZigBee devices are small sensors and input devices such as light switches: all those devices require low power and very low bandwidth. For these reasons, they can be easily powered with batteries and, since the devices are in a deep sleeping (low power consumption) state most of their time, the batteries can last for years and years. Moreover, the sensors are often installed in places not easily reachable, where an easy task as battery replacement could become very problematical.

The ZigBee protocol is based on the PHY and MAC layers of the OSI model and is suitable for wireless communication among devices in a 10 to 100 meters area. In order to use the ZigBee protocol, a company has to become a paying member of the Alliance, the device shall pass a compliant test in order to get the license, and rights have to be paid for it every year.

In a ZigBee network there are three types of devices:

• End Device, also called as RFD (reduced function devices): they are very simple devices which use only a part of the ZigBee protocol
• Router, also called as FFD (full function devices): they support all 802.15.4 functions and features and can communicate with a network coordinator
• Network coordinator: it is a special router which is in charge of the network configuration and management; there can be only one coordinator in a ZigBee network. Due to its important role, it requires more memory and CPU power than the other devices.

The IEEE 802.15.4 defines three operative bands for the ZigBee protocol:

The first band applies to the entire world; the second one is specific for the USA and the Pacific area, whereas the last one is reserved for Europe and Asia. For many types of applications, however, ZigBee is a too complex and expensive solution; several proprietary protocols compliant to the IEEE 802.15.4 standard are coming up and are proposing themselves as an alternative to ZigBee. Among them, there is the MiWi, the Microchip Wireless Networking Protocol. MiWi is a light and simple solution for short-range wireless communication on the 2.4 GHz band: only one frequency has been supported because Microchip wanted to create a product able to work all over the world; they did not want to make a custom or regional product. Even though it is still based on the IEEE 802.15.4 recommendation for Wireless Personal Area Networks (WPAN), it has fewer functions than ZigBee, and is suitable for customers who want simple networks able to operate with peer-to-peer, star, and meshed topologies.

Moreover, there no additional costs as in ZigBee, since no certifications is required; Microchip does not ask any fee for the protocol stack (downloadable from their site), assuming it is used with their PIC microcontrollers and with the MRF24J40 transceiver. MiWi is based on the MAC and PHY layers, but the network cannot be as wide as with a ZigBee based solution, and interoperability with other ZigBee devices is not supported. Another advantage of MiWi is that it requires simple and less expensive controllers, with less memory than those required by ZigBee networks.

From the hardware point of view, Microchip offers the MRF24J40 module (see the following figure), a 2.4 GHz wireless transceiver compliant with both ZigBee and the Microchip proprietary MiWi and MiWi P2P protocols. It has a built-in PCB antenna and, in conjunction with a Microchip PIC microcontroller, is suitable for applications such as industrial controls, home and building automation, lighting devices, low power sensors, remote monitoring.

The MRF24J40 is the first high frequency module produced by Microchip; it requires just few external components, is a low power device, and is able to provide performance even higher than those requested by the IEEE 802.15.4 standard. It is available in a 40-pin QFN package (6x6 millimeters), has a serial interface (SPI), and supports the Media Access Control (MAC) and the Advanced Encryption Standard (AES) with hardware coding.

Microchip offers also a development tool, called ZENA, which is a wireless network analyzer able to display the wireless network traffic on a graphical display. It is full compatible with ZigBee, MiWi and MiWi P2P devices and, through a packet sniffer functionality, can completely analyze and decode the traffic showing the decoded packets on the display. Moreover, ZENA is able to show the network topology, and capture all the messages flowing on the network. That tool is very powerful and useful, especially for people who have little or no experience at all with wireless networks. It is also possible to save on a file each test and debug session, for further analysis.
The demonstration board PICDEM Z by Microchip allows a fast prototyping and development of
wireless solutions, either with the ZigBee or MiWi protocol. The PICDEM Z kit contains all what is needed to develop a complete application:

• 2 PICDEM Z demo board, equipped with
  the 18F4620 PIC MCU
• 2 transceiver boards MRF24J40
• the ZENA tool
• the ZigBee and MiWi software protocol

Read the Italian version: MiWi: la soluzione di Microchip per reti wireless a corto raggio