優(yōu)化無線網(wǎng)絡(luò)實時的人機接口

　　本文討論了用于人機接口的不同無線接口，并評估了實時操作的不同功能。無線服務(wù)提供商，從硬實時標(biāo)準(zhǔn)如WirelessHART，基于ZigBee、Wi-Fi、藍牙、網(wǎng)格，都有自己要扮演的角色非常不同的時序要求使用Atmel、Freescale半導(dǎo)體器件和模塊和芯片。

　　有許多不同的無線技術(shù)可以提供到人接口的鏈接，給設(shè)計者很多機會優(yōu)化應(yīng)用程序的技術(shù)。

　　有些應(yīng)用程序需要硬實時能力。監(jiān)測一個關(guān)鍵的化學(xué)或核過程需要及時提供和顯示信息，傳感器和人類界面之間的聯(lián)系至關(guān)重要。如果無線技術(shù)是可行的技術(shù)，這必須是一個明確的、低延遲的解決方案。沒有這樣的系統(tǒng)就有可能產(chǎn)生失控的情況，在那里，人類控制器對舊數(shù)據(jù)做出反應(yīng)，使情況變得更糟。

　　Wireless versions of fieldbus protocols， such as WirelessHART， provide a way to deliver the real-time performance in a more flexible manner with wireless links. While it is based on the popular 2.4 GHz band， it also includes vital security and interference protection to ensure that every packet of information is delivered within a certain specified timeframe.

　　Many other industrial control applications do not require such time-critical links. Setting parameters on a screen can be done promptly for a human user but not require a hard real-time implementation. Robust yet flexible industrial protocols such as ZigBee， allow mesh networks to develop so that data can hop from one node to the next. This low-cost way of expanding a network creates challenges for implementing a real-time system， but is perfectly adequate for some human interface applications.