Bad_NotWritable: The access level does not allow writing to the Node

Ignition
1

Hello,

When I try to write data to a tag I get the following error message.

Bad_NotWritable: The access level does not allow writing to the Node.

I have created a few API endpoints using Web Dev as follows:

createTags - doPost

	basePath = request['data']['basePath']
	tags = request['data']['tags']
	collisionPolicy = request['data']['collisionPolicy']
	
	result = system.tag.configure(basePath, tags, collisionPolicy)

	return {'json': result}

tag - doPost

	paths = request['data']['paths']
	values = request['data']['values']

	result = system.tag.writeBlocking(paths, values)
	
	return {'json': result}

I create an additional tag in the Tag Provider [Sample_Tags] by calling createTags - doPost with the following body:

{
    "basePath": "[Sample_Tags]/Writeable",
    "tags": [
        {
            "name": "DeviceEUI",
            "opcItemPath" : "ns=2;s=[Sample_Tags]_Meta:Writeable/DeviceEUI",
            "opcServer": "Ignition OPC UA Server",
            "valueSource": "opc"
        }
    ],
    "collisionPolicy": "o"
}

The tag is created with the following result: (192 = “good”)

[
    {
        "code": 192
    }
]

If I want to write data to the tag using tag - doPost with the following body:

{
    "paths": ["[Sample_Tags]/Writeable/DeviceEUI", "[Sample_Tags]/Writeable/WriteableBoolean1"],
    "values": [12345, false]
}

I get the following message:

[
    {
        "code": -2147483136,
        "diagnosticMessage": "Bad_NotWritable: The access level does not allow writing to the Node."
    },
    {
        "code": 192
    }
]

So the predefined tag WriteableBoolean1 has a result of 192 = “good”. The other tag DeviceEUI that I defined myself gets an error message.

I suspect this is because I am trying to write to a tag which does not originates from a device that is defined in Ignition?

If so, how can I write to a tag which I have created dynamically from an external program (using the Web Dev API) and write to it? (using the same Web Dev API)

Thanks,

Simon.

2

You’re creating an OPC Tag pointing to an address in the simulator driver that doesn’t exist.

If you want to create an arbitrary tag then just create a Memory Tag instead, and don’t try to pretend it exists as part of some device/driver you don’t control.

3

Thanks Kevin. Specifying "valueSource": "memory" did the trick…

{
    "basePath": "[Sample_Tags]/Writeable",
    "tags": [
        {
            "name": "DeviceEUI",
            "opcItemPath" : "ns=2;s=[Sample_Tags]_Meta:Writeable/DeviceEUI",
            "opcServer": "Ignition OPC UA Server",
            "valueSource": "memory"
        }
    ],
    "collisionPolicy": "o"
}

Another question though. Where can I find all the settings for a tag definition and their explanations?

The reason why I am asking is the difficulty I have with e.g. the dataType property. See below.

If I try for example to specify the data type with "dataType": "string" as follows:

{
    "basePath": "[Sample_Tags]/Writeable",
    "tags": [
        {
            "name": "DeviceEUI",
            "dataType": "string",
            "opcItemPath" : "ns=2;s=[Sample_Tags]_Meta:Writeable/DeviceEUI",
            "opcServer": "Ignition OPC UA Server",
            "valueSource": "memory"
        }
    ],
    "collisionPolicy": "o"
}

I do see the data type is string in the OPC client:

image

But in the designer it is set to None:

image

And if I try to write to the tag with:

{
    "paths": ["[Sample_Tags]/Writeable/DeviceEUI"],
    "values": ["testing"]
}

I get:

[
    {
        "code": -1073741052,
        "diagnosticMessage": "Error trying to coerce 'testing' to a number."
    }
]

So if there is a complete overview of all the properties of the tag definition that would be a great help!

Thanks.

4

These doc pages should be useful:

https://docs.inductiveautomation.com/display/DOC81/system.tag.configure
https://docs.inductiveautomation.com/display/DOC81/Tag+Properties

If you find the “Data Type” tag property there’s a list of valid values in its Description column.

In your case I’m guessing it’s just a case sensitivity issue and you should be using String, not string.

All the OPC-related properties you cited in your last example should be removed as well, they don’t apply to Memory Tags.

1 Like