# ModBus TCP Read 64-bit registers
**URL:** https://discourse.nodered.org/t/modbus-tcp-read-64-bit-registers/25402
**Category:** Industrial
**Created:** [24 April 2020 07:11 UTC](https://discourse.nodered.org/t/modbus-tcp-read-64-bit-registers/25402 "2020-04-24T07:11:39Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@Job-Hoogeboom](https://discourse.nodered.org/u/Job-Hoogeboom)
#### Post date: [24 April 2020 07:11 UTC](https://discourse.nodered.org/t/modbus-tcp-read-64-bit-registers/25402/1 "2020-04-24T07:11:39Z")
Dear community members, I am trying to read some parameters from a Schneider Electric Smartlink SI D Power meter via Modbus TCP but I do not know how to read the Watthours, I can read the Voltage, Amperage, and Wattage, Those are of a Float32 format. The Modbus address for the Watthours is 3203 but it is an Int64 format. When I try to read it with Int32 it reads 0, When I try Int64 it gives an error.
Does someone know how to make this work?
Thanks!
---
### Author:  [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [24 April 2020 07:20 UTC](https://discourse.nodered.org/t/modbus-tcp-read-64-bit-registers/25402/2 "2020-04-24T07:20:15Z")
> [@Job-Hoogeboom](#):
>
> When I try Int64 it gives an error.
Can't really help if you don't show us the code and the error other than point you to the buffer documentation...
[Buffer | Node.js v21.5.0 Documentation](https://nodejs.org/api/buffer.html#buffer_buf_readbigint64be_offset)
---
### Author:  [@Job-Hoogeboom](https://discourse.nodered.org/u/Job-Hoogeboom)
#### Post date: [24 April 2020 07:34 UTC](https://discourse.nodered.org/t/modbus-tcp-read-64-bit-registers/25402/3 "2020-04-24T07:34:51Z")
I understand that Int64 isn't supported native by node-red, but is there an way to make it work?
---
### Author:  [@knolleary](https://discourse.nodered.org/u/knolleary)
#### Post date: [24 April 2020 08:00 UTC](https://discourse.nodered.org/t/modbus-tcp-read-64-bit-registers/25402/4 "2020-04-24T08:00:13Z")
Support for reading 64bit ints from Buffers was added in Node 12 - and note the function is called `readBigInt64BE ` not `readUInt64BE`.
They return a BigInt object, which has some particular behaviours you need to be aware of - [https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global\_Objects/BigInt](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt)
---
### Author:  [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [24 April 2020 08:01 UTC](https://discourse.nodered.org/t/modbus-tcp-read-64-bit-registers/25402/5 "2020-04-24T08:01:07Z")
Did you read the link? The function you called doesn't exist.
---
### Author:  [@Job-Hoogeboom](https://discourse.nodered.org/u/Job-Hoogeboom)
#### Post date: [24 April 2020 08:14 UTC](https://discourse.nodered.org/t/modbus-tcp-read-64-bit-registers/25402/6 "2020-04-24T08:14:11Z")
Okay I changed it to readBigInt64BE, it gives this error now.
---
### Author:  [@knolleary](https://discourse.nodered.org/u/knolleary)
#### Post date: [24 April 2020 08:16 UTC](https://discourse.nodered.org/t/modbus-tcp-read-64-bit-registers/25402/7 "2020-04-24T08:16:54Z")
Have you tried searching for the meaning of that error?
Sounds to me like your Buffer isn't big enough to contain a 64 bit number.
Pass the Buffer to a Debug node and share what it shows.
---
### Author:  [@Job-Hoogeboom](https://discourse.nodered.org/u/Job-Hoogeboom)
#### Post date: [24 April 2020 08:20 UTC](https://discourse.nodered.org/t/modbus-tcp-read-64-bit-registers/25402/8 "2020-04-24T08:20:25Z")
Not yet 😉
---
### Author:  [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [24 April 2020 08:21 UTC](https://discourse.nodered.org/t/modbus-tcp-read-64-bit-registers/25402/9 "2020-04-24T08:21:54Z")
Your buffer only has 4 bytes
4 X 8 = 32 bits
Get more data from the device and try again.
---
### Author:  [@Job-Hoogeboom](https://discourse.nodered.org/u/Job-Hoogeboom)
#### Post date: [24 April 2020 08:49 UTC](https://discourse.nodered.org/t/modbus-tcp-read-64-bit-registers/25402/10 "2020-04-24T08:49:03Z")
how can i get more data from the device? The modbus getter node just pulls the data from the Schneider power meter. the modbus table in the manual says its an Int64 format.
---
### Author:  [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [24 April 2020 09:09 UTC](https://discourse.nodered.org/t/modbus-tcp-read-64-bit-registers/25402/11 "2020-04-24T09:09:35Z")
no idea but have a look at the properties of the FC3 Hold Reg Read node called WattHours...
Isnt there a length or size or count property?
If the length is current 2 (i.e. 16bit WDs) then I'd guess double it to 4.
If its 4 (i.e. bytes) then double that to 8
Post a screen shot of its settings if you arent sure.
---
### Author:  [@Job-Hoogeboom](https://discourse.nodered.org/u/Job-Hoogeboom)
#### Post date: [24 April 2020 09:18 UTC](https://discourse.nodered.org/t/modbus-tcp-read-64-bit-registers/25402/12 "2020-04-24T09:18:46Z")
The field quantity was set at 2, I changed it to 4 it then gave this error. When I double it to 8 is gives the same error.
Thanks for your help btw!
---
### Author:  [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [24 April 2020 09:22 UTC](https://discourse.nodered.org/t/modbus-tcp-read-64-bit-registers/25402/13 "2020-04-24T09:22:13Z")
I'm pretty sure that is not a JS or NODE error (i.e. looks like a user coding error)
Can you share your flow?
Ps, buffer size now looks correct.
---
### Author:  [@knolleary](https://discourse.nodered.org/u/knolleary)
#### Post date: [24 April 2020 09:25 UTC](https://discourse.nodered.org/t/modbus-tcp-read-64-bit-registers/25402/14 "2020-04-24T09:25:20Z")
The reading of the 64bit Int is working. The error is now that a later part of your flow cannot handle the BigInt object type that has been returned by `redBigInt64BE`.
AS I said earlier, the BigInt object has some particular behaviours that will affect what you can do with it. You cannot treat it like just any other number.
> [@knolleary](#):
>
> They return a BigInt object, which has some particular behaviours you need to be aware of - [https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global\_Objects/BigInt](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt)
What do you want to do with it?
---
### Author:  [@Job-Hoogeboom](https://discourse.nodered.org/u/Job-Hoogeboom)
#### Post date: [24 April 2020 09:26 UTC](https://discourse.nodered.org/t/modbus-tcp-read-64-bit-registers/25402/16 "2020-04-24T09:26:50Z")
hope this works, newer shared a flow before lol 😉
---
### Author:  [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [24 April 2020 09:27 UTC](https://discourse.nodered.org/t/modbus-tcp-read-64-bit-registers/25402/17 "2020-04-24T09:27:17Z")
please edit that and put code between 3 back ticks (it is unusable in current format)
`````
`like this`
`````
---
### Author:  [@Job-Hoogeboom](https://discourse.nodered.org/u/Job-Hoogeboom)
#### Post date: [24 April 2020 09:27 UTC](https://discourse.nodered.org/t/modbus-tcp-read-64-bit-registers/25402/18 "2020-04-24T09:27:58Z")
```auto
[
{
"id": "e905007d.6be7b",
"type": "tab",
"label": "Flow 1",
"disabled": false,
"info": ""
},
{
"id": "ddb0454d.5233b8",
"type": "modbus-getter",
"z": "e905007d.6be7b",
"name": "FC 3 [150] (3027) Voltage",
"showStatusActivities": false,
"showErrors": false,
"logIOActivities": false,
"unitid": "150",
"dataType": "HoldingRegister",
"adr": "3027",
"quantity": "2",
"server": "ef18b8d5.36cf58",
"useIOFile": false,
"ioFile": "",
"useIOForPayload": false,
"x": 340,
"y": 80,
"wires": [
[],
[
"f4d32a73.d52f98"
]
]
},
{
"id": "d960f91.4d22d08",
"type": "modbus-getter",
"z": "e905007d.6be7b",
"name": "FC 3 [150] (3059) Wattage",
"showStatusActivities": false,
"showErrors": false,
"logIOActivities": false,
"unitid": "150",
"dataType": "HoldingRegister",
"adr": "3059",
"quantity": "2",
"server": "ef18b8d5.36cf58",
"useIOFile": false,
"ioFile": "",
"useIOForPayload": false,
"x": 340,
"y": 240,
"wires": [
[],
[
"c0203137.bf881"
]
]
},
{
"id": "d641fe0c.f9778",
"type": "modbus-getter",
"z": "e905007d.6be7b",
"name": "FC 3 [150] (2999) Amperage",
"showStatusActivities": false,
"showErrors": false,
"logIOActivities": false,
"unitid": "150",
"dataType": "HoldingRegister",
"adr": "2999",
"quantity": "2",
"server": "ef18b8d5.36cf58",
"useIOFile": false,
"ioFile": "",
"useIOForPayload": false,
"x": 340,
"y": 160,
"wires": [
[],
[
"af4ce282.20cc5"
]
]
},
{
"id": "1b77b382.24e7cc",
"type": "inject",
"z": "e905007d.6be7b",
"name": "",
"topic": "",
"payload": "true",
"payloadType": "bool",
"repeat": "60",
"crontab": "",
"once": false,
"onceDelay": 0.1,
"x": 90,
"y": 200,
"wires": [
[
"ddb0454d.5233b8",
"d641fe0c.f9778",
"d960f91.4d22d08",
"9e28e6fd.27fa08"
]
]
},
{
"id": "f4d32a73.d52f98",
"type": "function",
"z": "e905007d.6be7b",
"name": "ReadFloat 32",
"func": "const buf = Buffer.from(msg.payload.buffer);\nconst value = buf.readFloatBE();\nmsg.payload = {\"Voltage\": value};\n\nreturn msg;",
"outputs": 1,
"noerr": 0,
"x": 580,
"y": 80,
"wires": [
[
"206bb69e.ee399a"
]
]
},
{
"id": "af4ce282.20cc5",
"type": "function",
"z": "e905007d.6be7b",
"name": "ReadFloat 32",
"func": "const buf = Buffer.from(msg.payload.buffer);\nconst value = buf.readFloatBE();\nmsg.payload = {\"Amperage\": value};\n\nreturn msg;",
"outputs": 1,
"noerr": 0,
"x": 580,
"y": 160,
"wires": [
[
"206bb69e.ee399a"
]
]
},
{
"id": "c0203137.bf881",
"type": "function",
"z": "e905007d.6be7b",
"name": "ReadFloat 32",
"func": "const buf = Buffer.from(msg.payload.buffer);\nconst value = buf.readFloatBE();\nmsg.payload = {\"Wattage\": value};\n\nreturn msg;",
"outputs": 1,
"noerr": 0,
"x": 580,
"y": 240,
"wires": [
[
"206bb69e.ee399a"
]
]
},
{
"id": "206bb69e.ee399a",
"type": "join",
"z": "e905007d.6be7b",
"name": "",
"mode": "custom",
"build": "merged",
"property": "payload",
"propertyType": "msg",
"key": "topic",
"joiner": "\\n",
"joinerType": "str",
"accumulate": false,
"timeout": "",
"count": "4",
"reduceRight": false,
"reduceExp": "",
"reduceInit": "",
"reduceInitType": "",
"reduceFixup": "",
"x": 790,
"y": 200,
"wires": [
[
"4d324b86.d31414"
]
]
},
{
"id": "9e28e6fd.27fa08",
"type": "modbus-getter",
"z": "e905007d.6be7b",
"name": "FC 3 [150] (3203) Watthours",
"showStatusActivities": false,
"showErrors": false,
"logIOActivities": false,
"unitid": "150",
"dataType": "HoldingRegister",
"adr": "3203",
"quantity": "4",
"server": "ef18b8d5.36cf58",
"useIOFile": false,
"ioFile": "",
"useIOForPayload": false,
"x": 340,
"y": 320,
"wires": [
[],
[
"100ac95d.8381a7",
"d7e23e2d.658f4"
]
]
},
{
"id": "100ac95d.8381a7",
"type": "function",
"z": "e905007d.6be7b",
"name": "ReadInt 64",
"func": "const buf = Buffer.from(msg.payload.buffer);\nconst value = buf.readBigInt64BE()\nmsg.payload = {\"Energy\": value};\n\nreturn msg;",
"outputs": 1,
"noerr": 0,
"x": 590,
"y": 320,
"wires": [
[
"206bb69e.ee399a"
]
]
},
{
"id": "4d324b86.d31414",
"type": "debug",
"z": "e905007d.6be7b",
"name": "",
"active": true,
"tosidebar": true,
"console": false,
"tostatus": false,
"complete": "payload",
"targetType": "msg",
"x": 950,
"y": 200,
"wires": []
},
{
"id": "d7e23e2d.658f4",
"type": "debug",
"z": "e905007d.6be7b",
"name": "",
"active": true,
"tosidebar": true,
"console": false,
"tostatus": false,
"complete": "false",
"x": 580,
"y": 380,
"wires": []
},
{
"id": "ef18b8d5.36cf58",
"type": "modbus-client",
"z": "",
"name": "Smartlink SI D",
"clienttype": "tcp",
"bufferCommands": true,
"stateLogEnabled": false,
"tcpHost": "192.168.1.24",
"tcpPort": "502",
"tcpType": "DEFAULT",
"serialPort": "/dev/ttyUSB",
"serialType": "RTU-BUFFERD",
"serialBaudrate": "9600",
"serialDatabits": "8",
"serialStopbits": "1",
"serialParity": "none",
"serialConnectionDelay": "100",
"unit_id": 1,
"commandDelay": 20,
"clientTimeout": 1000,
"reconnectOnTimeout": false,
"reconnectTimeout": 2000,
"parallelUnitIdsAllowed": false
}
]
```
---
### Author:  [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [24 April 2020 09:31 UTC](https://discourse.nodered.org/t/modbus-tcp-read-64-bit-registers/25402/19 "2020-04-24T09:31:08Z")
what version of nodejs are you using?
at a command line terminal, enter `node -v`
> [@knolleary](#):
>
> Support for reading 64bit ints from Buffers was added in Node 12
---
### Author:  [@Job-Hoogeboom](https://discourse.nodered.org/u/Job-Hoogeboom)
#### Post date: [24 April 2020 09:32 UTC](https://discourse.nodered.org/t/modbus-tcp-read-64-bit-registers/25402/20 "2020-04-24T09:32:34Z")
i'm using version v12.14.1
---
### Author:  [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [24 April 2020 09:33 UTC](https://discourse.nodered.org/t/modbus-tcp-read-64-bit-registers/25402/21 "2020-04-24T09:33:44Z")
~Ah, so the join node or the http looks like its not liking the bigint?~
EDIT no - its part in the function
[Next page](https://discourse.nodered.org/t/modbus-tcp-read-64-bit-registers/25402.md?page=2)