# MQTT ---\> S7 PLC (node-red-contrib-s7comm)
**URL:** https://discourse.nodered.org/t/mqtt-s7-plc-node-red-contrib-s7comm/11868
**Category:** General
**Created:** [5 June 2019 13:39 UTC](https://discourse.nodered.org/t/mqtt-s7-plc-node-red-contrib-s7comm/11868 "2019-06-05T13:39:35Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@msw](https://discourse.nodered.org/u/msw)
#### Post date: [5 June 2019 13:39 UTC](https://discourse.nodered.org/t/mqtt-s7-plc-node-red-contrib-s7comm/11868/1 "2019-06-05T13:39:35Z")
Project purpose: To receive MQTT payload and write each msg element to a S7 PLC tag.
Payload
data - STRING[22]
datetime - STRING[20]
devaddr - STRING[8]
fcnt - REAL
port - REAL
rssi - REAL
I have been able to inject json string and real values in to the S7 PLC (see debug messages 3 & 4). However, I am having trouble writing each of the objects from debug message 1 in to the S7 PLC. I used a json & function node to isolate the data string and that doesn't work either.
Any advice on the correct format which I should be sending this data through the flow so it will be accepted by the s7comm:write node would be greatly appreciated.
Thanks.
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### Author:  [@msw](https://discourse.nodered.org/u/msw)
#### Post date: [11 June 2019 08:13 UTC](https://discourse.nodered.org/t/mqtt-s7-plc-node-red-contrib-s7comm/11868/2 "2019-06-11T08:13:17Z")
Solved!
The issue was the format in which the MQTT message was split and sent to the PLC. S7 PLC requires the message as a javascript object within an array.
The important line was msg.payload = json.stringify(data);
Previously I wasn't changing the payload to a json string properly before it flowed through the json node to convert to javascript object.
Debug window showing correct format of message.
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