Subscribing to MQTT Transmission Tags with paho.mqtt.client

Ignition
1

I have a Ignition Maker license running an MQTT Engine and MQTT Transmission Module.

I am using the Transmission Module to subscribe to the tags in this folder (topic):

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image777×564 57.1 KB

I’m able to subscribe to messages that the transmission module is publishing, I’m not having much luck decoding the message in a meaningful way.

Here is my function which decodes the message

def on_message(client,userdata, msg):

    topic=msg.topic
    m_decode=str(msg.payload.decode("utf-8","ignore"))

    print ('message received')
    print ('topic for this message: ', msg.topic)
    print ('raw payload: ',msg.payload)
    print ('payload with utf8 decoding:', m_decode, '\n')

Here is what the payload looks like, raw and decoded:

message received
topic for this message:  spBv1.0/default/DDATA/SWD/CATTLE CREEK INJECTION PAD 1
raw payload:  b'\x08\xb0\xc8\xe8\xc6\x8a0\x12E\n1SWD/CATTLE CREEK INJECTION PAD 1/ANNULUS PRESSURE\x18\xc7\xc0\xe8\xc6\x8a0 \t8\x00J\x00e\xf8u$C\x12D\n0SWD/CATTLE CREEK INJECTION PAD 1/TUBING PRESSURE\x18\xc7\xc0\xe8\xc6\x8a0 \t8\x00J\x00ezXsD\x12D\n0SWD/CATTLE CREEK INJECTION PAD 1/CASING PRESSURE\x18\xc9\xc0\xe8\xc6\x8a0 \t8\x00J\x00e\x13S\x1eE\x18o'
payload with utf8 decoding:Ɗ0E
1SWD/CATTLE CREEK INJECTION PAD 1/ANNULUS PRESSUREƊ0 	8 J eu$CD
0SWD/CATTLE CREEK INJECTION PAD 1/TUBING PRESSUREƊ0 	8 J ezXsDD
0SWD/CATTLE CREEK INJECTION PAD 1/CASING PRESSUREƊ0 	8 J eSEo
2

The messages are encoded in the format defined by Sparkplug.

It might be easier to consume them if you use one of the available Sparkplug client libraries.