I’m using Ignition to get PLC tags through the GE Industrial Gateway OPC Server which is the equivalent of the KEPServer OPC UA server. The OPC server is configured with a tag that is a Boolean array. I’m trying to figure out how to configure an Ignition tag to reference a bit in that array. The KEPServer tag has a length of 256. If I configure my Ignition with an OPC Item Path of something like “channel.device.KepTag” (like I do when referencing an array of floats) my tag quality goes to “Bad; unspecified”. If I append a 0 as the bit index to create an OPC Item Path of channel.device.KepTag.0 then the tag quality is good. Is that the required syntax for referencing a bit?
The syntax that constitutes a valid NodeId (OPC Item Path for an OPC tag from an OPC UA server) is entirely up to the OPC server. There is no client-side logic applied to OPC Item Paths that would isolate a bit inside a larger type for you.
I guess I didn’t word the question very well. I was hoping someone with experience using this OPC server could confirm that the syntax I’m using is required when using Ignition and this particular OPC server use case.
What I found is the address format channel.device.KepTag[X].Y is appropriate and I needed to treat the KEPServer tag as an array of 32-bit words. In order to reference the 61st element in the Boolean array I used a value of 1 for X and 28 for Y.