Encoding payloads for sparkplug_b_v1_0_Protobuf

Ignition Modules
1

I am gathering high-frequency data (1ms-5ms) from a JSON payload via OPC
I have attempted multiple methods using the traditional tag-based system.tag.writeBlocking() to transmit this data to our MQTT server, but the tag groups can only poll 1ms and it misses about 80% of the data.

I would like to take an input array of objects and transmit them iteratively using system.cirruslink.transmission.publish

Fiddling around, I have an input and an output from the google protobuf payload:

timestamp: 1664396472110
metrics {
  name: "pressure"
  timestamp: 1664396472110
  datatype: 9
  float_value: 173.15607
}
seq: 3

gets turned into

b"\x08\xae\xde\x8a\xae\xb80\x12\x18\n\x08pressure\x18\xae\xde\x8a\xae\xb80 \te\xf4'-C\x18\x03"

It’s not elegant, but I’d like to brute-force together a specific bytearray to transmit this data correctly.
Does anyone know the structure.pack formats for timestamp, float, etc?

2

There is much more complexity to a true Sparkplug Edge Node than simply using the protobuf encoding for a Sparkplug payload. You can certainly implement your own Sparkplug client - but it probably won’t be easy.

Instead, I would suggest looking at MQTT Engine custom namespaces. You can use a standard JSON payload encoding with the publish API. Take a look here: MQTT Engine Custom Namespace - MQTT Modules for Ignition 8.x - Confluence

With this method, you don’t have to deal with all of the ‘state’ aspects of Sparkplug and can simply publish your JSON based payloads to MQTT Engine.