概述

【T3000】边缘一体机中的【Modbus-请求】/【Modbus-解析】节点是配合【串口】节点使用的Modbus-RTU问询帧构造节点/Modbus-RTU应答帧解析节点。

【Modbus-请求】节点会根据用户填入的 "地址码"、"功能码"、"读取寄存器起始地址"、"读取寄存器数量"来生成对应的Modbus-RTU问询帧。

【Modbus-解析】节点会根据用户指定的【Modbus-请求】中的 "寄存器解析规则"来解析对应的Modbus-RTU应答帧。

PS-1: 【Modbus-请求】/【Modbus-解析】节点只用于问询帧构造/应答帧解析，通常要配合【串口】节点使用。

PS-2：由于Modbus问询帧和应答帧存在局限性， 例如使用者使用两个“Modbus请求”节点同时采集40001开始的两个寄存器和40005开始的两个寄存器时， 应答帧都是“01 03 04 …”结构的， 解析节点无法根据应答帧来分辨其所属的解析方式。 因而需要使用同一个“Modbus请求”节点同时采集40001-40006的所有寄存器后再分别做对应解析。

输入

【Modbus-请求】节点的输入：
#msg.payload 输入或输入内容通常根据FC(功能码)来确定
#当FC(功能码)为1、2、3、4时，msg.payload输入无意义，仅作节点激活作用。

#FC 5:写单个线圈（msg.payload:1/0）PS：1：开 / 0：关

#FC 6:写单个保持寄存器（msg.payload:0-65535） PS：要写入寄存器的内容

#FC15:写多个线圈（msg.payload:字节数组,每个字节表示8个线圈）PS：例如[0x15]表示00001111，0表示关、1表示开。 

#FC16:写多个保持寄存器（msg.payload:一个寄存器2个字节,要写入的具体字节数组,详见示例）
#PS:例如[0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x08] 表示写入4个寄存器的内容。

【Modbus-解析】节点的输入：
一般是串口节点输出的Modbus-RTU应答帧

输出

#Modbus-RTU问询帧/应答帧(buffer)
msg.payload

【Modbus-请求】节点配置项

【Modbus-请求】节点配置说明：

地址码:1-255 十进制数字输入

功能码:FC 1读线圈（功能码:0x01）
       FC 2读触点（功能码:0x02）
       FC 3读保持寄存器（功能码:0x03）
	   FC 4读输入寄存器（功能码:0x04）
	   FC 5写单个线圈（功能码:0x05）
	   FC 6写单个保持寄存器（功能码:0x06）
	   FC 15写多个线圈（功能码:0x0F）
	   FC 16写多个寄存器（功能码:0x10）
		 
起始地址:5位十进制数字,请根据厂家提供的数据寄存器表填写
		  功能码 寄存器起始地址(十进制)
            01          0xxxx
            02          1xxxx
            03          4xxxx
            04          3xxxx
            05          0xxxx
            06          4xxxx
            15          0xxxx
            16          4xxxx
		
数量:根据实际情况填写

寄存器解析:根据厂家提供的数据解析方法/实际情况填写

【Modbus-解析】节点配置项

选择要解析的Modbus-请求】节点即可。

示例

接入一个RS485传感器设备和一个RS232传感器设备并使用【串口】节点采集数据

节点接线图：

上图是设备厂家提供的RS485温湿度传感器说明书部分内容。

根据该内容，对RS485串口采集的【Modbus-请求】节点的配置应该为：

演示视频

node-red完整流程代码

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