How to send this HEX command to my device using Node-red

General
29

Your function code 2- works , as I've just done the same experiment.

var buf = Buffer.from([0xaa, 0x3f, 0x00, 0x00, 0xf0, 0x11]);
msg.payload = buf;
return msg;

1675152684200
16751526842002550×1358 285 KB

Code of my flow

[
    {
        "id": "4a65bd5989e6e48a",
        "type": "tab",
        "label": "流程 1",
        "disabled": false,
        "info": "",
        "env": []
    },
    {
        "id": "deb4b3071092f4b4",
        "type": "serial-port",
        "serialport": "/dev/ttyS4",
        "serialbaud": "9600",
        "databits": "8",
        "parity": "none",
        "stopbits": "1",
        "waitfor": "",
        "dtr": "none",
        "rts": "none",
        "cts": "none",
        "dsr": "none",
        "newline": "1",
        "bin": "false",
        "out": "time",
        "addchar": "",
        "responsetimeout": "10000"
    },
    {
        "id": "d4aee0b6830813cf",
        "type": "serial out",
        "z": "4a65bd5989e6e48a",
        "name": "",
        "serial": "deb4b3071092f4b4",
        "x": 400,
        "y": 320,
        "wires": []
    },
    {
        "id": "f0a90340ad0b821f",
        "type": "debug",
        "z": "4a65bd5989e6e48a",
        "name": "debug 1",
        "active": true,
        "tosidebar": true,
        "console": false,
        "tostatus": false,
        "complete": "false",
        "statusVal": "",
        "statusType": "auto",
        "x": 440,
        "y": 220,
        "wires": []
    },
    {
        "id": "daab7c3dfd21638b",
        "type": "function",
        "z": "4a65bd5989e6e48a",
        "name": "function 1",
        "func": "var buf = Buffer.from([0xaa, 0x3f, 0x00, 0x00, 0xf0, 0x11]);\nmsg.payload = buf;\nreturn msg;",
        "outputs": 1,
        "noerr": 0,
        "initialize": "",
        "finalize": "",
        "libs": [],
        "x": 220,
        "y": 280,
        "wires": [
            [
                "f0a90340ad0b821f",
                "d4aee0b6830813cf"
            ]
        ]
    },
    {
        "id": "782bddc5e8783cf7",
        "type": "inject",
        "z": "4a65bd5989e6e48a",
        "name": "",
        "props": [
            {
                "p": "payload"
            },
            {
                "p": "topic",
                "vt": "str"
            }
        ],
        "repeat": "",
        "crontab": "",
        "once": false,
        "onceDelay": 0.1,
        "topic": "",
        "payload": "",
        "payloadType": "date",
        "x": 150,
        "y": 200,
        "wires": [
            [
                "daab7c3dfd21638b"
            ]
        ]
    }
]