RS485 데이터 시트보기 (PDF) - National Instruments Corporation

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RS485

Wireless Sensor Network Serial Nodes

National Instruments Corporation 

Figure 1. WSN Serial Node Communication Model

The LabVIEW Serial Compatibility API helps you configure baud rate, stop bits, parity bits, and flow control. Using the API, you can initialize the serial channel, send commands to

the serial device, and then read back and parse the returned data, all locally without over-the-air communication and associated latency. Then you can send important data over

the air back to the WSN gateway/host machine via user-defined I/O variables (UDVs).

With the LabVIEW WSN Module, the custom applications are wirelessly downloaded to the node's onboard processor, and because these applications are written in the LabVIEW

graphical development environment, customizing node firmware is easy and does not require low-level assembly or machine code knowledge. With deployed LabVIEW WSN

code, you can also conduct local data analysis, respond to digital value changes or network status changes, and perform local control of the two digital I/O lines. The digital I/O

lines feature industrial ranges and can be configured for input, sinking output, and sourcing output.

Power

You can power the NI WSN measurement nodes with four 1.5 V AA alkaline or lithium battery cells. The node also features an external power port, so you can provide line power

or use other forms of power such as solar or vibration energy harvesting. The nodes support battery backup, meaning you can connect both external and battery power; the node

defaults to external power and automatically switches to battery power in the event the external power drops below a voltage threshold. The external power input should be used

to power NI WSN nodes operating in router mode, which is a feature that you can enable in software to set up a self-healing mesh network of nodes. Router nodes increase

density, distance, and redundancy in your wireless network.

Each node offers bidirectional digital I/O channels for input, sinking output, or sourcing output. You must use an external power supply to provide sourcing output through the

digital I/O channels, with a maximum total current output (aggregate on all channels) of 1 A. The serial nodes also feature a sensor power output channel, which delivers up to 50

mA at 12 V, and can be used to deliver power to external devices or sensors.

Battery Lifetime

With the flexibility of the node, you can specify baud rates, packet lengths, parity bits, stop bits, and flow control. Using LabVIEW WSN, you can customize the node to modify

transmit intervals (when data is passed back over the air to the gateway). These factors, among others, influence the battery-powered lifetime of the devices, as seen in the

following graphs. Results are typical, and you can assume 25 °C operating temperature, alkaline cells, sensor power turned off, and a single node network.

Figure 2. Serial Node Battery Life Versus Sample/Transmit Interval at Various Baud Rates

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