如何发送 Modbus RTU 命令来读取模拟输入

<h3 style="margin-top:24px;margin-right:0;margin-bottom:0;margin-left:0;padding:0 0 0 0 ;line-height:30px"><strong><span style="font-family: 宋体;color: rgb(34, 34, 34);letter-spacing: 0;font-size: 18px;background: rgb(255, 255, 255)"><span style="font-family:宋体">命令 0x04</span></span></strong></h3><p style="margin-top:24px;margin-right:0;margin-bottom:23px;margin-left:0;padding:0 0 0 0 ;line-height:30px"><span style="font-family: Arial;letter-spacing: 0;font-size: 18px;background: rgb(255, 255, 255)"><span style="font-family:宋体">该指令用于读取模拟输入</span> AI <span style="font-family:宋体">的值。</span></span></p><p style="margin-top:24px;margin-right:0;margin-bottom:23px;margin-left:0;padding:0 0 0 0 ;line-height:30px"><span style="font-family: Arial;letter-spacing: 0;font-size: 18px;background: rgb(255, 255, 255)"><span style="font-family:宋体">来自寄存器</span> # 30009 <span style="font-family:宋体">的 </span><span style="font-family:Arial">AI </span><span style="font-family:宋体">请求示例，请求设备地址 </span><span style="font-family:Arial">17 </span><span style="font-family:宋体">的 </span><span style="font-family:Arial">SlaveID</span><span style="font-family:宋体">。第一个寄存器的地址是 </span><span style="font-family:Arial">0008 hex = 8</span><span style="font-family:宋体">，因为 </span><span style="font-family:Arial">Account </span><span style="font-family:宋体">是从 </span><span style="font-family:Arial">0 </span><span style="font-family:宋体">地址维护的。</span></span></p><p><br/></p>