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modbus (1)

What is edge acquisition?

1. Introduction to edge acquisition

Edge acquisition is to abstract data (such as ModBus registers) on external devices (such as ModBus devices) into internal data points of the device (E870-D1). Configuring and reading internal data points is equivalent to configuring and reading corresponding external data ( such as ModBus registers). External devices can be ModBus devices or other communication protocol devices, such as IIC, CAN and other bus protocol devices. Currently, Ebyte E870-D1 only supports ModBus devices. (This article takes E870-D1 as an example)

2. The principle of edge acquisition

Implementation principle of edge acquisition (taking ModBus device as an example): As shown in the following edge acquisition application topology diagram, when edge acquisition data points are configured, the edge acquisition device (E870-D1) polls and reads the data in the external device through the ModBus protocol. The register is transmitted to the cloud platform through 4G;GPS Module when the cloud platform configures the data point, the edge acquisition device configures the corresponding register of the external device through the ModBus protocol, thus realizing the transparent transmission and control of the cloud platform and the external device.

The data structure of each data point includes the following attributes: "Enable", "Keyword", "Slave Address", "Register Type", "Register Address", "Data Type", "Report Mode", "Report Time" ", "Range of variation", "Number of decimal places", "Read-write property", "Up formula", "Down formula".

Among them, "keyword", "slave address", "register type", "register address", "read and write attributes" are used to realize the association between data points and ModBus registers.

The "keyword" is the name of the data point, and the name cannot be repeated in an edge acquisition device (E870-D1). When the cloud platform reads/configures the external device through the data point name ("keyword"), the edge acquisition The device (E870-D1) automatically translates the data point into the corresponding ModBus register according to its "Slave Address", "Register Type", "Register Address", and "Read-Write Attribute" information.

"Enable" controls whether the data point is valid. Only valid data points can be read, configured and polled.

Other attributes "Report Mode", "Report Time", "Variation Range", "Number of Decimals", "Upstream Formula", "Downstream Formula" can implement simple edge computing, which will be described in detail below.
2. The difference between edge collection and edge computing: Huawei's definition of edge computing (URL)

Huawei's definition of edge computing is: Edge computing is a distributed and open platform that integrates network, computing, storage, and application core capabilities at the edge of the network near the source of things or data to provide edge intelligent services nearby. To put it simply, edge computing is to analyze the data collected from the terminal directly in the local device or network where the data is generated, without the need to transmit the data to the cloud data processing center.

It is not difficult to see from the comparison between Huawei's definition of edge computing and the first description of the nature and principle of edge collection in this article. Edge collection belongs to a part of edge computing, that is, the part where the terminal collects data. At the same time, Ebyte E870-D1 has the function of transmitting data to the platform.
3. Problems solved by Ebyte E870-D1 edge acquisition:

1. Communication between ModBus and the platform: The traditional ModBus device is only short-distance communication. It is difficult to achieve communication with the Internet platform. Using Ebyte E870-D1, you can use its edge acquisition function to seamlessly connect to the local area. ModBus device and remote cloud platform, so as to realize unified monitoring and deployment of many ModBus devices by cloud platform.

2. Reduce the pressure on the platform server: Ebyte E870-D1 can easily add and delete data points through the "enable" attribute of data points, reduce unnecessary data point uploads, and at the same time "report mode", "report time" ” and “Variation range” can control the reporting timing of data points and reduce unnecessary reporting times of data points. The above can achieve a data filtering effect.

3. Simple edge computing can be realized: through the "upstream formula" and "downstream formula", custom addition, subtraction, multiplication and division calculations can be performed inside the Ebyte E870-D1.
Fourth, the advantages of Ebyte E870-D1 edge acquisition over ModBus_TCP:

1. Another way to achieve remote control of local ModBus devices is to use ModBus_TCP mode, but ModBus_TCP is not suitable for frequent data exchange and small amount of data each time, because it will consume a lot of network resources and platform resources. .

Today's sharply increased number of edge devices are all small, sophisticated, and highly specialized, such as a variety of sensors, each of which cannot be equipped with networking capabilities, and a huge number of edge devices are directly connected to the platform through ModBus_TCP , the pressure on the platform can also be imagined. Ebyte E870-D1 edge acquisition function can solve this problem very well.

2. Can connect to multiple external devices at the same time:Wireless modem Ebyte E870-D1 can connect to multiple edge acquisition devices at the same time, and ModBus_TCP can generally only communicate one-to-one.

3. The built-in IO can also be abstracted into data points: I explained how to abstract external device data into edge collection data points. At the same time, the DI, DO, AI, and AO that come with Ebyte E870-D1 can also be abstracted into structures. The same data points, thus eliminating the difference between built-in IO and external device data (such as DI, DO, AI, AO, etc.), reading/configuring built-in IO can use the same data structure, which is very helpful for platform development .

5. Usage scenarios

1. Connect multiple industrial DI, DO, AI, AO equipment to realize the network upgrade and transformation of traditional equipment.

2. Connect multiple ModBus sensors to realize environmental monitoring of an area.

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