# Writing Unsigned 32bit Integers to Modbus TCP Slave

**URL:** <https://discourse.nodered.org/t/writing-unsigned-32bit-integers-to-modbus-tcp-slave/94058>\
**Category:** General\
**Tags:** modbus\
**Created:** [20 December 2024 21:32 UTC](https://discourse.nodered.org/t/writing-unsigned-32bit-integers-to-modbus-tcp-slave/94058 "2024-12-20T21:32:43Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![bigfeetneedbigboots](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/bigfeetneedbigboots/32/33216_2.png) [@bigfeetneedbigboots](https://discourse.nodered.org/u/bigfeetneedbigboots)\
**Post date:** [20 December 2024 21:32 UTC](https://discourse.nodered.org/t/writing-unsigned-32bit-integers-to-modbus-tcp-slave/94058/1 "2024-12-20T21:32:43Z")

</div>

Hi all,

I'm reading modbus registers with U16 (Unsigned integer of 16-bit), U32, U64, S16 (Signed integer of 16-bit) and S32 integers and it's all working pretty well (except U64 ones, but I can deal with those later). The trouble is with writing data to some registers. I can, for example, write U16 registers successfully but am having trouble with U32.

Take register 40036 as an example. It is 2 bytes, Read-Write supported and U32. I can read the value in this register just fine. Home Assistant can write new values to this register just fine too. I just can't seem to write to this register with Node-RED.

An example message is {"value":15300,"fc":6,"unitid":247,"address":40036,"quantity":2}

I've tried sending different values such as "15300", [0,15300], [0,0,59,196] and so on.

The error I get is: Error: Modbus exception 2: Illegal data address (register not supported by device)

I've searched and reviewed various other posts (including [Writing 16bit/32 bit Signed Integers to Modbus TCP server on NodeRed](https://discourse.nodered.org/t/writing-16bit-32-bit-signed-integers-to-modbus-tcp-server-on-nodered/55370)) without luck.

```auto
[{"id":"2201f0b734fea824","type":"buffer-maker","z":"11d169a832e66cd4","name":"","specification":"spec","specificationType":"ui","items":[{"name":"item1","type":"uint32be","length":1,"dataType":"msg","data":"payload"}],"swap1":"","swap2":"","swap3":"","swap1Type":"swap","swap2Type":"swap","swap3Type":"swap","msgProperty":"payload","msgPropertyType":"str","x":790,"y":3000,"wires":[["43f5d323c10f84df","e1a8d2d69bfd1226"]]},{"id":"e1a8d2d69bfd1226","type":"buffer-parser","z":"11d169a832e66cd4","name":"","data":"payload","dataType":"msg","specification":"spec","specificationType":"ui","items":[{"type":"uint16be","name":"data","offset":0,"length":2,"offsetbit":0,"scale":"1","mask":""}],"swap1":"","swap2":"","swap3":"","swap1Type":"swap","swap2Type":"swap","swap3Type":"swap","msgProperty":"payload","msgPropertyType":"str","resultType":"value","resultTypeType":"output","multipleResult":true,"fanOutMultipleResult":false,"setTopic":true,"outputs":1,"x":990,"y":3000,"wires":[["a4e60b16523c27fb","aebe9ede.e25cf"]]},{"id":"2945b34038e247e4","type":"inject","z":"11d169a832e66cd4","name":"15200","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"write","payload":"15200","payloadType":"num","x":610,"y":3000,"wires":[["2201f0b734fea824"]]},{"id":"bd4625724d13ca31","type":"inject","z":"11d169a832e66cd4","name":"15300","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"write","payload":"15300","payloadType":"num","x":610,"y":2960,"wires":[["2201f0b734fea824"]]},{"id":"aebe9ede.e25cf","type":"modbus-write","z":"11d169a832e66cd4","name":"40036","showStatusActivities":false,"showErrors":true,"showWarnings":true,"unitid":"247","dataType":"HoldingRegister","adr":"40036","quantity":"1","server":"6f01e8e3a69bfa2f","emptyMsgOnFail":false,"keepMsgProperties":false,"delayOnStart":false,"startDelayTime":"","x":1170,"y":3000,"wires":[[],[]]},{"id":"6f01e8e3a69bfa2f","type":"modbus-client","name":"SigenStor","clienttype":"tcp","bufferCommands":true,"stateLogEnabled":false,"queueLogEnabled":false,"failureLogEnabled":true,"tcpHost":"192.168.1.33","tcpPort":"502","tcpType":"DEFAULT","serialPort":"/dev/ttyUSB","serialType":"RTU-BUFFERD","serialBaudrate":"9600","serialDatabits":"8","serialStopbits":"1","serialParity":"none","serialConnectionDelay":"100","serialAsciiResponseStartDelimiter":"0x3A","unit_id":1,"commandDelay":1,"clientTimeout":1000,"reconnectOnTimeout":true,"reconnectTimeout":2000,"parallelUnitIdsAllowed":true,"showErrors":false,"showWarnings":true,"showLogs":true}]

```

I need to also write signed 32 bit values, but seeking to resolve this issue first.

---

<div class="post-metadata">

**Author:** ![bigfeetneedbigboots](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/bigfeetneedbigboots/32/33216_2.png) [@bigfeetneedbigboots](https://discourse.nodered.org/u/bigfeetneedbigboots)\
**Post date:** [20 December 2024 22:05 UTC](https://discourse.nodered.org/t/writing-unsigned-32bit-integers-to-modbus-tcp-slave/94058/2 "2024-12-20T22:05:40Z")

</div>

Just in case it is helpful, this is how Home Assistant writes to register 40036 (successfully):

```auto
      - action: modbus.write_register
        data_template:
          hub: Sigen
          slave: 247
          address: 40036
          value:
            - >-
              {{ (states('input_text.set_sigen_pv_max_power_limit')| float * 1000) |
              round(0) | int // 2**16 }}
            - >-
              {{ (states('input_text.set_sigen_pv_max_power_limit')| float * 1000) |
              round(0) | int % 2**16 }}

```

---

<div class="post-metadata">

**Author:** ![bigfeetneedbigboots](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/bigfeetneedbigboots/32/33216_2.png) [@bigfeetneedbigboots](https://discourse.nodered.org/u/bigfeetneedbigboots)\
**Post date:** [20 December 2024 22:55 UTC](https://discourse.nodered.org/t/writing-unsigned-32bit-integers-to-modbus-tcp-slave/94058/3 "2024-12-20T22:55:54Z")

</div>

Figured it out. I need FC 16.

---

<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)\
**Post date:** [3 January 2025 22:56 UTC](https://discourse.nodered.org/t/writing-unsigned-32bit-integers-to-modbus-tcp-slave/94058/4 "2025-01-03T22:56:20Z")

</div>

This topic was automatically closed 14 days after the last reply. New replies are no longer allowed.