Modbus temperature sensor

General
1

Hi everyone,

I'm trying to read temperature and humidity using my Raspberry pi4 form a Modbus sensor http://www.bizkit.ru/wp-content/uploads/2018/11/Temperature-and-humidity-transmitter-SHT20-sensor-Modbus-RS485.pdf
using this rs485 Hat I bought here
https://www.hwhardsoft.de/english/projects/rs485-shield/.
I've enabled the serial port and tried a simple flow
[{"id":"3b180a5b.d295d6","type":"modbus-read","z":"e1207341.1c3be","name":"","topic":"","showStatusActivities":true,"logIOActivities":false,"showErrors":true,"unitid":"1","dataType":"InputRegister","adr":"0","quantity":"2","rate":"10","rateUnit":"s","delayOnStart":false,"startDelayTime":"","server":"df79ccb6.da1de","useIOFile":false,"ioFile":"","useIOForPayload":false,"x":160,"y":120,"wires":[["6cd15ba8.778df4"],]},{"id":"df79ccb6.da1de","type":"modbus-client","z":"","name":"","clienttype":"simpleser","bufferCommands":false,"stateLogEnabled":false,"queueLogEnabled":false,"tcpHost":"127.0.0.1","tcpPort":"502","tcpType":"DEFAULT","serialPort":"/dev/serial0","serialType":"RTU-BUFFERD","serialBaudrate":"9600","serialDatabits":"8","serialStopbits":"1","serialParity":"none","serialConnectionDelay":"100","unit_id":1,"commandDelay":100,"clientTimeout":100,"reconnectOnTimeout":true,"reconnectTimeout":2000,"parallelUnitIdsAllowed":true}
It seems there is something wrong: at the beginning I see below the read node a green icon connected but when it tries to polling I get an error "Modbus Failure On State connected Get More About It By Logging".
I didin't wire the shield ground since the sensor works with a different powre supply and I measured 4 Volts between the sensor power supply ground and shield ground, but from what I've read that should work even without groud wire.
Could someone help me?

Thank you

2

Your flow is not importable. Please edit your post above (pencil icon) and format your flow as per the forum guide - How to share code or flow json

3

Sorry!!

[{"id":"3b180a5b.d295d6","type":"modbus-read","z":"e1207341.1c3be","name":"","topic":"","showStatusActivities":true,"logIOActivities":false,"showErrors":true,"unitid":"1","dataType":"InputRegister","adr":"0","quantity":"2","rate":"10","rateUnit":"s","delayOnStart":false,"startDelayTime":"","server":"df79ccb6.da1de","useIOFile":false,"ioFile":"","useIOForPayload":false,"x":160,"y":120,"wires":[["6cd15ba8.778df4"],[]]},{"id":"df79ccb6.da1de","type":"modbus-client","z":"","name":"","clienttype":"simpleser","bufferCommands":false,"stateLogEnabled":false,"queueLogEnabled":false,"tcpHost":"127.0.0.1","tcpPort":"502","tcpType":"DEFAULT","serialPort":"/dev/serial0","serialType":"RTU-BUFFERD","serialBaudrate":"9600","serialDatabits":"8","serialStopbits":"1","serialParity":"none","serialConnectionDelay":"100","unit_id":1,"commandDelay":100,"clientTimeout":100,"reconnectOnTimeout":true,"reconnectTimeout":2000,"parallelUnitIdsAllowed":true}]
4

11

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22825×477 41 KB

5

Hi rromele,
First of all thank's for your reply!!
I tried to modify as per your suggestion

[{"id":"e1207341.1c3be","type":"tab","label":"Test","disabled":false,"info":""},{"id":"3b180a5b.d295d6","type":"modbus-read","z":"e1207341.1c3be","name":"","topic":"","showStatusActivities":true,"logIOActivities":false,"showErrors":true,"unitid":"1","dataType":"InputRegister","adr":"2","quantity":"2","rate":"10","rateUnit":"s","delayOnStart":false,"startDelayTime":"","server":"df79ccb6.da1de","useIOFile":false,"ioFile":"","useIOForPayload":false,"x":150,"y":100,"wires":[[],["2d255fca.a8626"]]},{"id":"2d255fca.a8626","type":"modbus-response","z":"e1207341.1c3be","name":"","registerShowMax":20,"x":470,"y":180,"wires":[]},{"id":"df79ccb6.da1de","type":"modbus-client","z":"","name":"","clienttype":"serial","bufferCommands":true,"stateLogEnabled":true,"queueLogEnabled":true,"tcpHost":"127.0.0.1","tcpPort":"502","tcpType":"DEFAULT","serialPort":"/dev/serial0","serialType":"RTU-BUFFERD","serialBaudrate":"9600","serialDatabits":"8","serialStopbits":"1","serialParity":"none","serialConnectionDelay":"100","unit_id":"4","commandDelay":"100","clientTimeout":"100","reconnectOnTimeout":true,"reconnectTimeout":"2000","parallelUnitIdsAllowed":true}]

But it still doesn't work

The strange thing is that as soon as I start node red I got those error messages

19 May 18:17:36 - [warn] [modbus-read:3b180a5b.d295d6] Modbus Failure On State sending Get More About It By Logging
19 May 18:17:36 - [error] [modbus-read:3b180a5b.d295d6] Timed out
19 May 18:17:36 - [error] [modbus-read:3b180a5b.d295d6] TypeError: Cannot read property 'status' of undefined

then it returns on connected until it tries to ask for data again..

I'm very new at this world and I have no idea on what is happening and I'm getting depressed :smile:

Thank you!!

6

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