"""

Example ussage of the read_multi_vars function

This was tested against a S7-319 CPU

"""

import ctypes

import struct

import snap7

from snap7.common import check_error

from snap7.snap7types import S7DataItem, S7AreaDB, S7WLByte

client = snap7.client.Client()

client.connect('10.100.5.2', 0, 2)

data_items = (S7DataItem * 3)()

data_items[0].Area = ctypes.c_int32(S7AreaDB)

data_items[0].WordLen = ctypes.c_int32(S7WLByte)

data_items[0].Result = ctypes.c_int32(0)

data_items[0].DBNumber = ctypes.c_int32(200)

data_items[0].Start = ctypes.c_int32(16)

data_items[0].Amount = ctypes.c_int32(4) # reading a REAL, 4 bytes

data_items[1].Area = ctypes.c_int32(S7AreaDB)

data_items[1].WordLen = ctypes.c_int32(S7WLByte)

data_items[1].Result = ctypes.c_int32(0)

data_items[1].DBNumber = ctypes.c_int32(200)

data_items[1].Start = ctypes.c_int32(12)

data_items[1].Amount = ctypes.c_int32(4) # reading a REAL, 4 bytes

data_items[2].Area = ctypes.c_int32(S7AreaDB)

data_items[2].WordLen = ctypes.c_int32(S7WLByte)

data_items[2].Result = ctypes.c_int32(0)

data_items[2].DBNumber = ctypes.c_int32(200)

data_items[2].Start = ctypes.c_int32(2)

data_items[2].Amount = ctypes.c_int32(2) # reading an INT, 2 bytes

# create buffers to receive the data

# use the Amount attribute on each item to size the buffer

for di in data_items:

# create the buffer

buffer = ctypes.create_string_buffer(di.Amount)

# cast the pointer to the buffer to the required type

pBuffer = ctypes.cast(ctypes.pointer(buffer),

ctypes.POINTER(ctypes.c_uint8))

di.pData = pBuffer

result, data_items = client.read_multi_vars(data_items)

for di in data_items:

check_error(di.Result)

# struct formats

fmts = ['>f', '>f', '>h']

# unpack and print the result of each read

for i in range(0, len(data_items)):

fmt = fmts[i]

di = data_items[i]

foo = ''.join([chr(di.pData[i]) for i in range(0, di.Amount)])

fnum = struct.unpack(fmt, foo)[0]

print(fnum)

client.disconnect()

client.destroy()