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Merge pull request gijzelaerr#28 from lance5107B/master
Add support for Cli_ReadMultiVars
2 parents eeaea98 + 272a6a8 commit 8e2dd94

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‎example/read_multi.py‎

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"""
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Example ussage of the read_multi_vars function
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This was tested against a S7-319 CPU
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"""
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import ctypes
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import struct
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import snap7
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from snap7.common import check_error
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from snap7.snap7types import S7DataItem, S7AreaDB, S7WLByte
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client = snap7.client.Client()
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client.connect('10.100.5.2', 0, 2)
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data_items = (S7DataItem * 3)()
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data_items[0].Area = ctypes.c_int32(S7AreaDB)
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data_items[0].WordLen = ctypes.c_int32(S7WLByte)
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data_items[0].Result = ctypes.c_int32(0)
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data_items[0].DBNumber = ctypes.c_int32(200)
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data_items[0].Start = ctypes.c_int32(16)
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data_items[0].Amount = ctypes.c_int32(4) # reading a REAL, 4 bytes
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data_items[1].Area = ctypes.c_int32(S7AreaDB)
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data_items[1].WordLen = ctypes.c_int32(S7WLByte)
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data_items[1].Result = ctypes.c_int32(0)
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data_items[1].DBNumber = ctypes.c_int32(200)
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data_items[1].Start = ctypes.c_int32(12)
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data_items[1].Amount = ctypes.c_int32(4) # reading a REAL, 4 bytes
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data_items[2].Area = ctypes.c_int32(S7AreaDB)
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data_items[2].WordLen = ctypes.c_int32(S7WLByte)
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data_items[2].Result = ctypes.c_int32(0)
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data_items[2].DBNumber = ctypes.c_int32(200)
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data_items[2].Start = ctypes.c_int32(2)
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data_items[2].Amount = ctypes.c_int32(2) # reading an INT, 2 bytes
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# create buffers to receive the data
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# use the Amount attribute on each item to size the buffer
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for di in data_items:
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# create the buffer
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buffer = ctypes.create_string_buffer(di.Amount)
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# cast the pointer to the buffer to the required type
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pBuffer = ctypes.cast(ctypes.pointer(buffer),
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ctypes.POINTER(ctypes.c_uint8))
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di.pData = pBuffer
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result, data_items = client.read_multi_vars(data_items)
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for di in data_items:
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check_error(di.Result)
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# struct formats
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fmts = ['>f', '>f', '>h']
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# unpack and print the result of each read
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for i in range(0, len(data_items)):
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fmt = fmts[i]
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di = data_items[i]
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foo = ''.join([chr(di.pData[i]) for i in range(0, di.Amount)])
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fnum = struct.unpack(fmt, foo)[0]
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print(fnum)
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client.disconnect()
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client.destroy()

‎snap7/client.py‎

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@@ -228,6 +228,17 @@ def write_area(self, area, dbnumber, start, data):
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return self.library.Cli_WriteArea(self.pointer, area, dbnumber, start,
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size, wordlen, byref(cdata))
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def read_multi_vars(self, items):
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"""This function read multiple variables from the PLC.
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:param items: list of S7DataItem objects
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:returns: a tuple with the return code and a list of data items
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"""
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result = self.library.Cli_ReadMultiVars(self.pointer, byref(items),
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c_int32(len(items)))
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check_error(result, context="client")
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return result, items
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def list_blocks(self):
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"""Returns the AG blocks amount divided by type.
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‎snap7/snap7types.py‎

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@@ -164,3 +164,15 @@ def __str__(self):
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" SDB: %s>" % (self.OBCount, self.FBCount, self.FCCount,
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self.SFBCount, self.SFCCount, self.DBCount,
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self.SDBCount)
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class S7DataItem(ctypes.Structure):
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_pack_ = 1
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_fields_ = [
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('Area', ctypes.c_int32),
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('WordLen', ctypes.c_int32),
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('Result', ctypes.c_int32),
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('DBNumber', ctypes.c_int32),
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('Start', ctypes.c_int32),
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('Amount', ctypes.c_int32),
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('pData', ctypes.POINTER(ctypes.c_uint8))
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]

‎test/test_client.py‎

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import ctypes
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import struct
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import unittest
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import logging
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import time
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from subprocess import Popen
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from os import path, kill
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import snap7
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from snap7.snap7exceptions import Snap7Exception
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from snap7.snap7types import S7AreaDB, S7WLByte, S7DataItem
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logging.basicConfig(level=logging.WARNING)
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def test_db_get(self):
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self.client.db_get(db_number=db_number)
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def test_read_multi_vars(self):
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db = 1
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# build and write test values
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test_value_1 = 129.5
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test_bytes_1 = bytearray(struct.pack('>f', test_value_1))
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self.client.db_write(db, 0, test_bytes_1)
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test_value_2 = -129.5
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test_bytes_2 = bytearray(struct.pack('>f', test_value_2))
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self.client.db_write(db, 4, test_bytes_2)
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test_value_3 = -123
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test_bytes_3 = bytearray(struct.pack('>h', test_value_3))
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self.client.db_write(db, 8, test_bytes_3)
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test_values = [test_value_1, test_value_2, test_value_3]
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# build up our requests
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data_items = (S7DataItem * 3)()
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data_items[0].Area = ctypes.c_int32(S7AreaDB)
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data_items[0].WordLen = ctypes.c_int32(S7WLByte)
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data_items[0].Result = ctypes.c_int32(0)
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data_items[0].DBNumber = ctypes.c_int32(db)
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data_items[0].Start = ctypes.c_int32(0)
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data_items[0].Amount = ctypes.c_int32(4) # reading a REAL, 4 bytes
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data_items[1].Area = ctypes.c_int32(S7AreaDB)
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data_items[1].WordLen = ctypes.c_int32(S7WLByte)
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data_items[1].Result = ctypes.c_int32(0)
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data_items[1].DBNumber = ctypes.c_int32(db)
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data_items[1].Start = ctypes.c_int32(4)
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data_items[1].Amount = ctypes.c_int32(4) # reading a REAL, 4 bytes
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data_items[2].Area = ctypes.c_int32(S7AreaDB)
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data_items[2].WordLen = ctypes.c_int32(S7WLByte)
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data_items[2].Result = ctypes.c_int32(0)
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data_items[2].DBNumber = ctypes.c_int32(db)
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data_items[2].Start = ctypes.c_int32(8)
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data_items[2].Amount = ctypes.c_int32(2) # reading an INT, 2 bytes
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# create buffers to receive the data
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# use the Amount attribute on each item to size the buffer
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for di in data_items:
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# create the buffer
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dataBuffer = ctypes.create_string_buffer(di.Amount)
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# get a pointer to the buffer
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pBuffer = ctypes.cast(ctypes.pointer(dataBuffer),
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ctypes.POINTER(ctypes.c_uint8))
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di.pData = pBuffer
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result, data_items = self.client.read_multi_vars(data_items)
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result_values = []
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# struct formats to match data_items[] above
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fmts = ['>f', '>f', '>h']
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# unpack and test the result of each read
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for i in xrange(0, len(data_items)):
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fmt = fmts[i]
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di = data_items[i]
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bytes_str = ''.join([chr(di.pData[j]) for j in range(0, di.Amount)])
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result_values.append(struct.unpack(fmt, bytes_str)[0])
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self.assertEqual(result_values[0], test_values[0])
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self.assertEqual(result_values[1], test_values[1])
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self.assertEqual(result_values[2], test_values[2])
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def test_upload(self):
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"""
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this raises an exception due to missing authorization? maybe not

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