i'm currently writing a python skript which interacts with a PLC via OPC UA.
The communication with OPC UA seems very slow.
I measured the time for writing 5 values to the PLC with time.perf_counter()
which results in 20ms.
Eventually im trying to write/read up to 100 variables in one cycle. This would result in a cyclic time of 2sec.
The PLC ist connected to the PC via a switch.
The 5 variables I tested: _node are Node objects; statusword is in ushort(hex); the others are int
opc.set_value(self.statusword_node, get_statusnumber(self.statusword))
opc.set_value(self.actualspeed_node, self.actualspeed)
opc.set_value(self.errorcode_node, self.errorcode)
opc.set_value(self.motorcurrent_node,self.motorcurrent)
opc.set_value(self.motortorque_node, self.motortorque)
opc is an object from my OpcClient class. set_value is the follwing function:
def set_value(node: Node, value) -> None:
'''sets value to node object'''
node.set_value(get_uadatatype(value))
the function get_uadatatype() returns the value as a uadatatype:
def get_uadatatype(value) -> ua.DataValue:
'''checks the type of value and converts it into a ua.DataValue type'''
if isinstance(value, bool):
return ua.DataValue(ua.Variant(value, ua.VariantType.Boolean))
elif isinstance(value, int) or isinstance(value, np.uint16):
return ua.DataValue(ua.Variant(value, ua.VariantType.Int16))
elif isinstance(value, float):
return ua.DataValue(ua.Variant(value, ua.VariantType.Float))
else:
loginfo(f"Please import convert function for {type(value)}")
raise ValueError
Which part of the programm slows it down? Or is it just impossible to write values faster with opc?
Thanks for your help:)
What slows you down is the network. Each set_value, does a network request/response with the server.
To speed things up you need to do a batch write:
nodes = [
self.statusword_node,
self.actualspeed_node,
...
]
values = [
get_statusnumber(self.statusword),
self.actualspeed,
...
]
opc.set_values(nodes, values)