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7133867.3R_Datasheet PDF

时间:2021-06-14 02:18:59 来源:网络整理编辑:OWON Technology Lilliput Electronics

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Similarly, the remaining five loads can be calculated by carrying out the same operations on the remaining five rows of the inverse matrix. Doing so yields the following loading conditions:

Similarly, the remaining five loads can be calculated by carrying out the same operations on the remaining five rows of the inverse matrix. Doing so yields the following loading conditions:

7133867.3R_Datasheet PDF

The PHY (which stands for physical”) is the lowest layer in the network. This is the part that actually transmits and receives RF (radio frequency) signals. With regard to the ZigBee, Simple MAC, and SNAP solutions presented later in this paper; the PHY is based on the IEEE 802.15.4 standard.

The term Stack refers to the software that actually defines the communications protocols and the data/control packets that are to be passed around the network. The MAC (Media Access Control) layer is software that interfaces the Stack to the PHY. Finally, the Application Layer is the software that interfaces the stack to the outside world. In the case of an End Device, for example, the Application Layer will be in charge of monitoring signals from any sensors and controlling any actuators. The software MAC, Stack, and Application Layers all run on a microprocessor, which also resides on the RF Engine.

Off-The-Shelf ZigBee Solutions With regard to the previous topic, it is important to note that many people consider ZigBee and the IEEE 802.15.4 standard to be synonymous, but this is not the case. In fact, the term ZigBee refers to a particular Stack implementation that sits on top of the 802.15.4 PHY and 802.15.4 MAC layers. However, it is true that the 802.15.4 MAC is often referred to as the ZigBee MAC” as illustrated in Fig 6 .

7133867.3R_Datasheet PDF

7133867.3R_Datasheet PDF

It is common to see advertisements for off-the-shelf” ZigBee solutions boasting: Easy Wireless with ZigBee Technology” . As many users have discovered at great expense, however, designing, implementing, and configuring a ZigBee-based wireless network is not a trivial task. In reality, there is no Easy Wireless with ZigBee” and there are no off-the-shelf ZigBee wireless network solutions. Instead, there is off-the-shelf ZigBee hardware, which developers have to use as a starting point to build up into a working solution. This can consume a substantial amount of financial and engineering resources and can easily take nine months (or more).

Combined, the MAC and ZigBee Stack occupy around 60 KB of memory and consume a relatively large amount of power. On top of this, the developer has to create an application layer that interfaces the ZigBee stack with the outside world. In addition to requiring a high level of expertise, designing and implementing an applications layer can be time-consuming and resource-intensive. Furthermore, in the case of cost-conscious systems with limited memory resources, the relatively large size of the MAC and Stack combo can significantly restrict the amount of memory available to the applications layer.

The main advantages associated with a full ZigBee solution are as follows:

The main disadvantages associated with a full ZigBee solution are as follows:

Do-It-Yourself Simple MAC-based Solutions As an alternative to using an off-the-shelf” ZigBee solution as discussed in the previous topic, some developers opt to create a custom network from the ground up. This usually involves licensing and modifying an existing Simple MAC to create a Custom MAC, then developing a Custom Stack, and then developing the Application Layer (Fig 7 ).