AN-201G LoRaWAN Strain Gauge Sensor User Guide

Device Information: Model AN-201G, devEui ffffff100004e9c8, gateway IP 192.168.31.205, Modbus Slave ID 10, BACnet Device ID 109

1 Protocol Overview

The AN-201G reports RS485 Modbus register data, battery voltage, and signal quality on Fport 210.

1.1 Uplink Data Protocol (Fport 210)

Payload format (Fport 210):

Each Type byte determines the field name and the number of following value bytes:

JavaScript Decoder Example:

// AN-201G Vibrating-Wire Strain Gauge — Fport 210 uplink decoder
function decodeUplink(bytes) {
  var i = 1, r = {}, freqCount = 0, tempCount = 0;
  function u16(b,o){ return (b[o]<<8)|b[o+1]; }
  function i16(b,o){ var v=u16(b,o); return v>32767?v-65536:v; }
  function u32(b,o){ return ((b[o]<<24)|(b[o+1]<<16)|(b[o+2]<<8)|b[o+3])>>>0; }
  while (i < bytes.length) {
    var t = bytes[i++];
    switch (t) {
      case 0x01: r.model     = bytes[i++]; break;
      case 0x94: r.rs485Addr = bytes[i++]; break;
      case 0x04: r.batteryVoltage = u16(bytes,i)/1000; i+=2; break; // V
      case 0x05: r.batteryLowEvent= bytes[i++]; break;
      case 0xDC: {
        // 4-byte uint32 ÷100 = Hz; first = current, second = initial
        var hz = u32(bytes,i)/100; i+=4;
        if(freqCount===0){ r.frequency=hz; } else { r.initialFrequency=hz; }
        freqCount++; break;
      }
      case 0xAA: {
        // int16 ÷10 = °C; first = current, second = initial
        var tc = i16(bytes,i)/10; i+=2;
        if(tempCount===0){ r.temperature=tc; } else { r.initialTemperature=tc; }
        tempCount++; break;
      }
      case 0xDD: r.vibratingWireSensorModel = bytes[i++]; break;
      case 0x95: { var len=bytes[i++]; i+=len; break; } // Modbus block (optional)
      default:   i++; break;
    }
  }
  return r;
}
// → { model:98, rs485Addr:1, frequency:1234.56, temperature:25.3,
//     initialFrequency:1200.0, initialTemperature:20.0, ... }

Script download: LPP.zip

Compatibility note: LPP.js is developed and tested against ChirpStack v4.17.0. The ChirpStack JavaScript codec API may differ across versions — if you are running a different ChirpStack version, review and adjust the script as needed before deployment.

Gateway-Calculated Strain Output (not in raw payload)

The AN-201G does not report stress/strain values directly. The gateway's LPP.js decoder derives them from the raw frequency and temperature data using the vibrating-wire surface strain formula. The computed fields are available via all IoT Hub interfaces:

Formula (for sensor model code 0x01 — concrete/steel surface):

F  = f² / 1000          (frequency digit, where f is in Hz)
steelStructureStrain   = G × C × (F₁ − F₀)                  [µε]
concreteStructureStrain= steelStructureStrain + (Y₁ − Y₂) × (T₁ − T₀)  [µε]

Access the derived strain values:

frequencyDigit (reg 16, AI 10909) and initialFrequencyDigit (reg 23, AI 10913)
are also exposed for reference.

2 Getting Uplink Data

⚠️ The IP addresses (192.168.31.205 / 192.168.31.193), ChirpStack API token, Slave ID, BACnet Device ID, and devEui in the examples below are for demonstration only. Replace them with your actual gateway IP, ChirpStack API token, and device parameters.

2.1 ChirpStack MQTT Subscription

Subscribe to the MQTT topic to receive real-time uplink frames:

Application ID — 3ef9e6b9-ec54-4eda-86b8-a5fb46899f39 is the factory-default ChirpStack
application built into the gateway. Replace it with your actual application
ID if you have created a different one.

Gateway IP — 192.168.31.205 is the gateway WAN port IP shown as an
example. Replace it with your actual gateway IP address.

Device EUI — ffffff100004e9c8 is the EUI of the example device.
Replace it with the EUI shown in the gateway device list, or use +
as a wildcard to subscribe to all devices at once.

# Subscribe to one specific device
mosquitto_sub -h 192.168.31.205 -p 1883 \
  -u gateway -P mqtt88888888 \
  -t "application/3ef9e6b9-ec54-4eda-86b8-a5fb46899f39/device/ffffff100004e9c8/event/up"

# Subscribe to ALL devices on ALL applications (wildcard)
mosquitto_sub -h 192.168.31.205 -p 1883 \
  -u gateway -P mqtt88888888 \
  -t "application/+/device/+/event/up"

Example uplink payload (JSON):

{
  "devEui": "ffffff100004e9c8",
  "fPort": 210,
  "object": {
    ...  (decoded LPP fields)
  }
}

2.2 IoT Hub HTTP API

Send a GET request to retrieve the latest device state:

curl -s "http://192.168.31.205:8070/api/getStatus?devEui=ffffff100004e9c8"
{
  "success": true,
  "result": {
    "batteryVoltage": 3.53,
    "batteryVoltageState": 0,
    "timestamp": 1775015242,
    "vibratingWireSensorModel": 1,
    "frequency": 859.92,
    "frequencyDigit": 739.46,
    "temperature": 26.8,
    "correctionFactor": 1,
    "initialFrequency": 856.61,
    "initialFrequencyDigit": 733.78,
    "initialTemperature": 27.6,
    "steelStructureStrain": 21.02,
    "concreteStructureStrain": 19.58,
    "batteryLowAlarm": false,
    "isHeartbeat": true,
    "model": "AN-201G"
  }
}

2.3 IoT Hub Modbus TCP — Python Script

Script download: modbus_tcp_read.py

Use modbus_tcp_read.py to poll all registers at once:

python3 modbus_tcp_read.py --ip 192.168.31.205 --port 502 \
    --slaveId 10 --sensorType AN-201G
Target: 192.168.31.205:502 | Slave ID: 10 | Sensor: AN-201G
================================================================================================================================================================
Attribute                | Addr   | FC  | Format     | Order        | Cnt | Scale    | Raw(Hex)            | Value              | Unit
----------------------------------------------------------------------------------------------------------------------------------------------------------------
online                   | 6      | 03  | Bit/Bool   | Big(ABCD)    | 1   | x1       | 0001                | true               | none
lastOnlineTime           | 7      | 03  | UnixTime   | Big(ABCD)    | 2   | x1       | 69CC 9537           | 1775015223         | second
batteryVoltage           | 9      | 03  | Int16(S)   | Big(ABCD)    | 1   | /100     | 0161                | 3.53               | volt
batteryVoltageState      | 10     | 03  | Int16      | Big(ABCD)    | 1   | x1       | 0000                | 0.0                | none
timestamp                | 11     | 03  | Int32      | Big(ABCD)    | 2   | x1       | 69CC 954A           | 1775015242.0       | seconds
vibratingWireSensorModel | 13     | 03  | Int16      | Big(ABCD)    | 1   | x1       | 0001                | 1.0                | none
frequency                | 14     | 03  | Float32    | Big(ABCD)    | 2   | /100     | 47A7 F400           | 859.92             | Hz
frequencyDigit           | 16     | 03  | Float32    | Big(ABCD)    | 2   | /100     | 4790 6D00           | 739.46             | digit
temperature              | 18     | 03  | Int16(S)   | Big(ABCD)    | 1   | /100     | 0A78                | 26.8               | celsius
correctionFactor         | 19     | 03  | Float32    | Big(ABCD)    | 2   | /10000   | 461C 4000           | 1.0000             | none
initialFrequency         | 21     | 03  | Float32    | Big(ABCD)    | 2   | /100     | 47A7 4E80           | 856.61             | Hz
initialFrequencyDigit    | 23     | 03  | Float32    | Big(ABCD)    | 2   | /100     | 478F 5100           | 733.78             | digit
... (20 fields total)

2.4 IoT Hub Modbus TCP — Modbus Poll

Tool download: Modbus Poll 9.5.0.1507.zip

1. Open Modbus Poll, connect to 192.168.31.205:502, Slave ID 10
2. Menu Setup → Read/Write Definition, set Function Code = FC03, Start Address = 6, Length = 64
3. Click OK — values update in real-time

2.5 IoT Hub BACnet BIP — Python Script

Script download: bacnet_read.py

Use bacnet_read.py to read all BACnet objects:

python3 bacnet_read.py --ip 192.168.31.205 --port 47808 --id 109
Target: 192.168.31.205:47808 | BACnet ID: 109 | Scan: 10900-10999
------------------------------------------------------------
Type | Instance | Offset | Value                    | Object Name
------------------------------------------------------------
BI   | 10902    | 2      | active                   | ffffff100004e9c8.online
AI   | 10903    | 3      | 1775015168.00            | ffffff100004e9c8.lastOnlineTime
AI   | 10904    | 4      | 3.53                     | ffffff100004e9c8.batteryVoltage
AI   | 10905    | 5      | 0.00                     | ffffff100004e9c8.batteryVoltageState
AI   | 10906    | 6      | 1775015296.00            | ffffff100004e9c8.timestamp
AI   | 10907    | 7      | 1.00                     | ffffff100004e9c8.vibratingWireSensorModel
AI   | 10908    | 8      | 859.92                   | ffffff100004e9c8.frequency
AI   | 10909    | 9      | 739.46                   | ffffff100004e9c8.frequencyDigit
AI   | 10910    | 10     | 26.80                    | ffffff100004e9c8.temperature
AI   | 10911    | 11     | 1.00                     | ffffff100004e9c8.correctionFactor
AI   | 10912    | 12     | 856.61                   | ffffff100004e9c8.initialFrequency
AI   | 10913    | 13     | 733.78                   | ffffff100004e9c8.initialFrequencyDigit
... (20 objects total)

2.6 IoT Hub BACnet BIP — YABE

Tool download: SetupYabe_v2.1.0.exe

1. Open YABE, connect to 192.168.31.205:47808
2. Expand Device 109 in the device tree
3. Browse AI/BI/AV/BV/CV objects to view real-time values