使用我前面几篇博文的内容,能够使用Python编写一个最简单的OPC UA /ModbusTCP网关。
从这个程序可以看出:
- 应用OPC UA 并不难,现在我们就可以应用到工程应用中,甚至DIY项目也可以。不必采用复杂的工具软件。
- 使用Python 来构建工业自动化领域的原型机程序是不错的选择。
OPCUA_modbus 网关
import sys
sys.path.insert(0, "..")
import time
from opcua import Server
from pyModbusTCP.client import ModbusClient # Modbus TCP Client
from pyModbusTCP import utils
if __name__ == "__main__":
# setup our server
server = Server()
server.set_endpoint("opc.tcp://127.0.0.1:48400/freeopcua/server/")
# setup our own namespace, not really necessary but should as spec
uri = "http://examples.freeopcua.github.io"
idx = server.register_namespace(uri)
# get Objects node, this is where we should put our nodes
objects = server.get_objects_node()
# populating our address space
myobj = objects.add_object(idx, "MyObject")
myvar = myobj.add_variable(idx, "MyVariable", 6.7)
myvar.set_writable() # Set MyVariable to be writable by clients
ModbusInterface = ModbusClient(host="localhost", port=502, unit_id=1, auto_open=True, auto_close=False)
# starting!
server.start()
try:
count = 0
while True:
time.sleep(1)
reg_l=ModbusInterface.read_input_registers(0,2)
val=utils.word_list_to_long(reg_l)
print(utils.decode_ieee(val[0],False))
myvar.set_value(utils.decode_ieee(val[0],False))
finally:
#close connection, remove subcsriptions, etc
server.stop()
modbusTCP服务器程序
import argparse
from pyModbusTCP.server import ModbusServer, DataBank
from pyModbusTCP import utils
from datetime import datetime
import numpy as np
Fs = 8000
f = 50
x=0
coil_state=True
class MyDataBank(DataBank):
"""A custom ModbusServerDataBank for override get_holding_registers method."""
def __init__(self):
# turn off allocation of memory for standard modbus object types
# only "holding registers" space will be replaced by dynamic build values.
super().__init__(virtual_mode=True)
def get_coils(self, address, number=1, srv_info=None):
global coil_state
coil_state=not coil_state
return coil_state
def get_holding_registers(self, address, number=1, srv_info=None):
"""Get virtual holding registers."""
# populate virtual registers dict with current datetime values
now = datetime.now()
return now.second
def get_input_registers(self, address, number=1, srv_info=None):
global x
wave=np.sin(2 * np.pi * f * x / Fs)*10
x=x+1
b32_l=[utils.encode_ieee(wave,False)]
b16_l = utils.long_list_to_word(b32_l)
print(b16_l)
return b16_l
if __name__ == '__main__':
# parse args
parser = argparse.ArgumentParser()
parser.add_argument('-H', '--host', type=str, default='localhost', help='Host (default: localhost)')
parser.add_argument('-p', '--port', type=int, default=502, help='TCP port (default: 502)')
args = parser.parse_args()
# init modbus server and start it
server = ModbusServer(host=args.host, port=args.port, data_bank=MyDataBank())
server.start()
最后透过uaExpert 程序访问OPCUA Server。可以看到myVar 变量在变化。
OPCUA 客户端
import sys
sys.path.insert(0, "..")
import numpy as np
import matplotlib.pyplot as plt
from opcua import Client
x = np.arange(0,1000,1,dtype=np.int16)
y=np.arange(-10,10,0.02,dtype=np.float32)
if __name__ == "__main__":
client = Client("opc.tcp://localhost:48400/freeopcua/server/")
# client = Client("opc.tcp://admin@localhost:4840/freeopcua/server/") #connect using a user
try:
client.connect()
# Client has a few methods to get proxy to UA nodes that should always be in address space such as Root or Objects
root = client.get_root_node()
print("Objects node is: ", root)
# Node objects have methods to read and write node attributes as well as browse or populate address space
print("Children of root are: ", root.get_children())
while True:
myvar = root.get_child(["0:Objects", "2:MyObject", "2:MyVariable"])
obj = root.get_child(["0:Objects", "2:MyObject"])
print("myvar is: ", myvar.get_value())
y=np.append(y,myvar.get_value())
y=np.delete(y, 0, axis=0)
plt.clf()
plt.plot(x, y, ls="-", lw=2, label="plot figure")
plt.legend()
plt.show()
plt.pause(0.1)
# Stacked myvar access
# print("myvar is: ", root.get_children()[0].get_children()[1].get_variables()[0].get_value())
finally:
client.disconnect()
看出来了吧这些程序都短小精悍。编写程序是学习计算机网络协议最好的方法。