Thanks and apologies I didn’t make myself clear.
I’m using sparkplug.encodePayload(payload) where payload is the JSON the second example above as you’ve pointed out JSON isn’t what’s on the wire.
I’m just wanting to conform to the specification. I want in the DBIRTH to pass engineering units and the unique id of each wireless sensor of which there can be 100s of sensors with multiple metrics per sensor. There doesn’t seem to be a sparkplug b validator and I don’t have anything to test against as it’s just POV at this stage…