PROSAGA码农传奇-MQTT/MODBUS-如何通过Modbus TCP发送'struct.pack'类型？

<div class =“post-text”itemprop =“text”>
  <UL>
    <LI>
      起初你可以使用
      <a href="https://github.com/riptideio/pymodbus" rel="nofollow noreferrer">
        pymodbus
      </A>
       具有很多功能的库。
    </LI>
    <LI>
      也
       <code>
 struct.pack()
 </code>
       不支持列表作为参数。
    </LI>
    <LI>
       <code>
 0001 0000 0006 11 03 006B 0003
 </code>
       是Modbus-TCP数据包的标准示例，其中包含：
    </LI>
  </UL>
  <BLOCKQUOTE>
    
       <code>
 0001: Transaction Identifier
 </code>
    
    
       <code>
 0000: Protocol Identifier
 </code>
    
    
       <code>
 0006: Message Length (6 bytes to follow)
 </code>
    
    
       <code>
 11: The Unit Identifier (17 = 11 hex)
 </code>
    
    
       <code>
 03: The Function Code (read Analog Output Holding Registers)
 </code>
    
    
       <code>
 006B: The Data Address of the first register requested. (40108-40001 = 107 =6B hex)
 </code>
    
    
       <code>
 0003: The total number of registers requested. (read 3 registers 40108 to 40110)
 </code>
    
    
      <子>
        <a href="http://www.simplymodbus.ca/TCP.htm" rel="nofollow noreferrer">
          参考
        </A>
      </子>
    
  </BLOCKQUOTE>
  
    因此，您可以创建一个
    
      MODBUS-TCP
    
     包含以上示例的数据包：
  
   <pre>
 <code>
 import struct

transaction = 0x0001
identifier = 0x0000
length = 0x0006
unitid = 0x11
fcode = 0x03  # Holding register fcode.
reg_addr = 0x006B  # Register address.
count = 0x0003  # Read three register.

total_pack_string = '0x{:04x}{:04x}{:04x}{:02x}{:02x}{:04x}{:04x}'.format(
    transaction, identifier, length, unitid, fcode, reg_addr, count
)
total_pack_hex = hex(int(total_pack_string, 16))

'''Or with using pack method.'''
pack_ = struct.pack(
   '>HHHBBHH', transaction, identifier, length, unitid, fcode, reg_addr, count
)

# Then send the pack_ or total_pack_hex using a TCP-Socket.

</code>
 </pre>
  <HR />
  
    [
    的
      注意
    </强>
    ]：
  
  <UL>
    <LI>
       <code>
 transaction
 </code>
       是2Byte ==短==
       <code>
 H
 </code>
    </LI>
    <LI>
       <code>
 identifier
 </code>
       是2Byte ==短==
       <code>
 H
 </code>
    </LI>
    <LI>
       <code>
 length
 </code>
       是2Byte ==短==
       <code>
 H
 </code>
    </LI>
    <LI>
       <code>
 unitid
 </code>
       是1Byte ==
       <code>
 B
 </code>
    </LI>
    <LI>
       <code>
 fcode
 </code>
       是1Byte ==
       <code>
 B
 </code>
    </LI>
    <LI>
       <code>
 reg_addr
 </code>
       是2Byte ==短==
       <code>
 H
 </code>
    </LI>
    <LI>
       <code>
 count
 </code>
       是2Byte ==短==
       <code>
 H
 </code>
    </LI>
    <LI>
       <code>
 B
 </code>
       是
       <code>
 unsigned byte
 </code>
    </LI>
    <LI>
       <code>
 H
 </code>
       是
       <code>
 unsigned short
 </code>
    </LI>
  </UL>
  
    因此，格式将是这样的
     <code>
 >HHHBBHH
 </code>
  
  <HR />
  <H1>
    运用
    <a href="https://github.com/riptideio/pymodbus" rel="nofollow noreferrer">
      pymodbus
    </A>
     当量：
  </H1>
   <pre>
 <code>
 from pymodbus.client.sync import ModbusTcpClient

unitid = 0x11
fcode = 0x03  # Holding register fcode.
reg_addr = 0x006B  # Register address.
count = 0x0003  # Read three register.

cli = ModbusTcpClient('127.0.0.1', port=502)

if cli.connect():
    res = cli.read_holding_registers(reg_addr, count=count, unit=unitid)