Modbus 協議傳輸的資料一般只有基本的 U16 型態,但在實際應用上可能因裝置不同而有不同的應用,例如長整數、浮點數,但又因為硬體 CPU/MCU/OS 實際狀況而有位元順序的問題,底下是 python 轉換函式…
def Convert( theType, values ):
if( theType == 'FLOAT(ABCD)' ):
packit = struct.pack('>hh',values[0],values[1])
tobytes = struct.unpack('>4c', packit)
packit = struct.pack('>4c',tobytes[0],tobytes[1],tobytes[2],tobytes[3])
set_value = struct.unpack('>f', packit)[0]
elif( theType == 'FLOAT(CDAB)' ):
packit = struct.pack('>hh',values[0],values[1])
tobytes = struct.unpack('>4c', packit)
packit = struct.pack('>4c',tobytes[2],tobytes[3],tobytes[0],tobytes[1])
set_value = struct.unpack('>f', packit)[0]
elif( theType == 'FLOAT(BADC)' ):
packit = struct.pack('>hh',values[0],values[1])
tobytes = struct.unpack('>4c', packit)
packit = struct.pack('>4c',tobytes[1],tobytes[0],tobytes[3],tobytes[2])
set_value = struct.unpack('>f', packit)[0]
elif( theType == 'FLOAT(DCBA)' ):
packit = struct.pack('>hh',values[0],values[1])
tobytes = struct.unpack('>4c', packit)
packit = struct.pack('>4c',tobytes[3],tobytes[2],tobytes[1],tobytes[0])
set_value = struct.unpack('>f', packit)[0]
elif( theType == 'UINT32(ABCD)' ):
packit = struct.pack('>hh',values[0],values[1])
tobytes = struct.unpack('>4c', packit)
packit = struct.pack('>4c',tobytes[0],tobytes[1],tobytes[2],tobytes[3])
set_value = struct.unpack('>L', packit)[0]
elif( theType == 'UINT32(CDAB)' ):
packit = struct.pack('>hh',values[0],values[1])
tobytes = struct.unpack('>4c', packit)
packit = struct.pack('>4c',tobytes[2],tobytes[3],tobytes[0],tobytes[1])
set_value = struct.unpack('>L', packit)[0]
elif( theType == 'UINT32(BADC)' ):
packit = struct.pack('>hh',values[0],values[1])
tobytes = struct.unpack('>4c', packit)
packit = struct.pack('>4c',tobytes[1],tobytes[0],tobytes[3],tobytes[2])
set_value = struct.unpack('>L', packit)[0]
elif( theType == 'UINT32(DCBA)' ):
packit = struct.pack('>hh',values[0],values[1])
tobytes = struct.unpack('>4c', packit)
packit = struct.pack('>4c',tobytes[3],tobytes[2],tobytes[1],tobytes[0])
set_value = struct.unpack('>L', packit)[0]
elif( theType == 'INT32(ABCD)' ):
packit = struct.pack('>hh',values[0],values[1])
tobytes = struct.unpack('>4c', packit)
packit = struct.pack('>4c',tobytes[0],tobytes[1],tobytes[2],tobytes[3])
set_value = struct.unpack('>l', packit)[0]
elif( theType == 'INT32(CDAB)' ):
packit = struct.pack('>hh',values[0],values[1])
tobytes = struct.unpack('>4c', packit)
packit = struct.pack('>4c',tobytes[2],tobytes[3],tobytes[0],tobytes[1])
set_value = struct.unpack('>l', packit)[0]
elif( theType == 'INT32(BADC)' ):
packit = struct.pack('>hh',values[0],values[1])
tobytes = struct.unpack('>4c', packit)
packit = struct.pack('>4c',tobytes[1],tobytes[0],tobytes[3],tobytes[2])
set_value = struct.unpack('>l', packit)[0]
elif( theType == 'INT32(DCBA)' ):
packit = struct.pack('>hh',values[0],values[1])
tobytes = struct.unpack('>4c', packit)
packit = struct.pack('>4c',tobytes[3],tobytes[2],tobytes[1],tobytes[0])
set_value = struct.unpack('>l', packit)[0]
elif( theType == 'UINT16(AB)' ):
packit = struct.pack('>h',values[0])
tobytes = struct.unpack('>2c', packit)
packit = struct.pack('>cc',tobytes[0],tobytes[1])
set_value = struct.unpack('>H', packit)[0]
elif( theType == 'UINT16(BA)' ):
packit = struct.pack('>h',values[0])
tobytes = struct.unpack('>2c', packit)
packit = struct.pack('>cc',tobytes[1],tobytes[0])
set_value = struct.unpack('>H', packit)[0]
elif( theType == 'INT16(AB)' ):
packit = struct.pack('>h',values[0])
tobytes = struct.unpack('>2c', packit)
packit = struct.pack('>cc',tobytes[0],tobytes[1])
set_value = struct.unpack('>h', packit)[0]
elif( theType == 'INT16(BA)' ):
packit = struct.pack('>h',values[0])
tobytes = struct.unpack('>2c', packit)
packit = struct.pack('>cc',tobytes[1],tobytes[0])
set_value = struct.unpack('>h', packit)[0]
else:
set_value = values[0]
return set_value
#Modbus 讀值可能是 2byte 也可能是 4byte
values = [-4370,-8756]
Convert( 'FLOAT(ABCD)' ,values )
Convert( 'FLOAT(DCBA)' ,values )
Convert( 'FLOAT(BADC)' ,values )
Convert( 'FLOAT(CDAB)' ,values )
Convert( 'UINT32(ABCD)' ,values )
Convert( 'UINT32(DCBA)' ,values )
Convert( 'UINT32(BADC)' ,values )
Convert( 'UINT32(CDAB)' ,values )
Convert( 'INT32(ABCD)' ,values )
Convert( 'INT32(DCBA)' ,values )
Convert( 'INT32(BADC)' ,values )
Convert( 'INT32(CDAB)' ,values )
Convert( 'UINT16(AB)' ,values )
Convert( 'INT16(AB)' ,values )
Convert( 'INT16(BA)' ,values )
Convert( 'UINT16(BA)' ,values )
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