The more I and my colleague look at it, the more it looks like bytes are being swapped around, similar to the issue observed here, except my modbus master and slave are entirely in node-red, so I don't know why this is happening.
as a test, I broadcast 12345 on 4008, and receive as much in my node-red client, but my colleague receives alternating FF 00 and 00 FF his end.
He said:
Almost like it’s only using 8 bits and maxing out at 255, then either shifting or endian swapping it
Can you clarify your overall goal?
If you simply want to read/write values from a MitsiPLC, you can use node-red-contrib-mcprotocol
If you need to build a modbus server, then you should read the built in docs. For example, would be better off writing to the modbus server using the flex-write.
Built in help...
You can use the Modbus write nodes (FC) to write data to the server buffers.
You can use the Modbus read nodes (FC) to read data from the server buffers.
Here is how i would structure it:
My apologies for the delay in replying; I was called to other tasks by my work.
The overall goal with this system is to re-broadcast signals received from a PLC, but the best my colleague is seeing is the same replies coming back with alternating 8 bit “halves” of the 16 bit data, even when I broadcast 12345. I think we need to do a byte swap using buffer-parser, but I've never got anything but errors from the buffer-parser node.
Current flow is (possibly broken? been a while):
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"z": "37f1be47da815ae1",
"name": "Brown & Carroll Modbus re-server",
"info": "",
"x": 920,
"y": 100,
"wires": []
},
{
"id": "f4d3a0e92cc61648",
"type": "modbus-write",
"z": "37f1be47da815ae1",
"g": "49c18e3ad19acbda",
"name": "",
"showStatusActivities": false,
"showErrors": false,
"showWarnings": true,
"unitid": "1",
"dataType": "HoldingRegister",
"adr": "60",
"quantity": "1",
"server": "06fb380adab7a3ac",
"emptyMsgOnFail": false,
"keepMsgProperties": false,
"delayOnStart": false,
"startDelayTime": "",
"x": 1140,
"y": 440,
"wires": [
[],
[]
]
},
{
"id": "509b5b5744b44bea",
"type": "inject",
"z": "37f1be47da815ae1",
"g": "49c18e3ad19acbda",
"name": "",
"props": [
{
"p": "payload"
},
{
"p": "topic",
"vt": "str"
}
],
"repeat": "",
"crontab": "",
"once": false,
"onceDelay": 0.1,
"topic": "",
"payload": "69",
"payloadType": "num",
"x": 970,
"y": 440,
"wires": [
[
"f4d3a0e92cc61648"
]
]
},
{
"id": "2b2b6e5bf6a1669d",
"type": "inject",
"z": "37f1be47da815ae1",
"g": "49c18e3ad19acbda",
"name": "",
"props": [
{
"p": "payload"
},
{
"p": "topic",
"vt": "str"
}
],
"repeat": "5",
"crontab": "",
"once": true,
"onceDelay": 0.1,
"topic": "",
"payload": "",
"payloadType": "date",
"x": 710,
"y": 560,
"wires": [
[
"67a752c86bc8ca3c"
]
]
},
{
"id": "67a752c86bc8ca3c",
"type": "function",
"z": "37f1be47da815ae1",
"g": "49c18e3ad19acbda",
"name": "Debug 12345 to D408",
"func": "// debug\nmsg.payload = {\n 'value': 12345, 'register': 'holding',\n 'address': 8, 'disableMsgOutput': 0\n};\nreturn msg;",
"outputs": 1,
"noerr": 0,
"initialize": "",
"finalize": "",
"libs": [],
"x": 900,
"y": 560,
"wires": [
[
"bdc07397e20610c1",
"5d59c82badda5237"
]
]
},
{
"id": "bdc07397e20610c1",
"type": "debug",
"z": "37f1be47da815ae1",
"g": "49c18e3ad19acbda",
"name": "debug 12345",
"active": true,
"tosidebar": true,
"console": false,
"tostatus": false,
"complete": "payload",
"targetType": "msg",
"statusVal": "",
"statusType": "auto",
"x": 1030,
"y": 520,
"wires": []
},
{
"id": "d8b07ddb.c44d4",
"type": "modbus-client",
"name": "Boiler_PLC",
"clienttype": "tcp",
"bufferCommands": true,
"stateLogEnabled": false,
"queueLogEnabled": false,
"failureLogEnabled": false,
"tcpHost": "192.168.127.2",
"tcpPort": "502",
"tcpType": "DEFAULT",
"serialPort": "/dev/ttyUSB",
"serialType": "RTU-BUFFERD",
"serialBaudrate": "9600",
"serialDatabits": "8",
"serialStopbits": "1",
"serialParity": "none",
"serialConnectionDelay": "100",
"serialAsciiResponseStartDelimiter": "",
"unit_id": "1",
"commandDelay": "1",
"clientTimeout": "1000",
"reconnectOnTimeout": true,
"reconnectTimeout": "2000",
"parallelUnitIdsAllowed": true
},
{
"id": "06fb380adab7a3ac",
"type": "modbus-client",
"name": "nodered_local_server",
"clienttype": "tcp",
"bufferCommands": true,
"stateLogEnabled": false,
"queueLogEnabled": false,
"failureLogEnabled": true,
"tcpHost": "127.0.0.1",
"tcpPort": "10502",
"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,
"showWarnings": true,
"showLogs": true
}
]
I tried doing something like that, but the server doesn't appear in the list of writable objects. I added a Modbus flex getter to the server's input, but that just gave us zeroes, so I had to revert in the end.
Some the weirdness my end was caused by Modbus broadcasting single-number arrays, rather than single numbers. Fixed with simple functions. Solution to that issue here
Issue still remains with byte-swapping on my colleague's end.
Solution: Turns out there was an error on my colleague's side, where his software was reading from addresses 4001, where it should have been reading from address 1 as they were already denoted as holding registers to begin with and didn't need the 400 preamble.
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