The SmartSampler supports integration of Modbus RTU-compatible sensors via the RS-485 interface. Configuration is done using the built-in GUI and flexible parsing rules to extract values from custom responses.
🧩 Overview
- Protocol: Modbus RTU
- Supported Functions: Manual polling via Function Code 0x03 (Read Holding Registers)
- Transport: RS-485, half-duplex
- Live Reading Toggle: ON/OFF toggle for periodic polling
- Multi-register support: Handles multi-variable sensors
- Custom Parsing: Extract and decode values using flexible configuration strings
🛠 RS-485 Sensor Configuration
The configuration text box allows you to define multiple Modbus sensors using a structured comma-separated string.
Format:
sensor_name,address,register,label,bytes,scaling,offset,orderParameters:
| Field | Description |
|---|---|
sensor_name | Group name used in logs (e.g., LeadMed) |
address | Modbus slave ID (decimal format, e.g., 1) |
register | Register start address in decimal (e.g., 0 for 0x0000) |
label | Variable name shown in output (e.g., temp, do, do_percent) |
bytes | Number of bytes to read (e.g., 4 for a float32 or 2 registers) |
scaling | Multiplier to scale the raw value (e.g., 1.0 or 0.01) |
offset | Value added after scaling (e.g., 0) |
order | Byte order pattern using letters A, B, C, D |
Example Entries:
LeadMed,1,0,temp,4,1.0,0,ABCD
LeadMed,1,290,do,4,1.0,0,ABCD
LeadMed,1,292,do_percent,4,1.0,0,ABCDLive Reading
- When Live Reading is toggled ON, the SmartSampler continuously polls configured sensors.
- Each Modbus message is built using the configured Device ID and Register Address.
- Responses are decoded using the selected DataType and mapped to A–D placeholders.
- New values appear in the Live Reading box as timestamped entries.
📶 Baud Rate
- Supported:
9600,19200,38400, etc. (Selectable via dropdown) - Saving applies the rate and restarts the Modbus bus
💾 Save & Load
- Press Save to store current configuration.
- Press Load to retrieve previously saved settings.
🧰 Notes for Developers
- Message format follows:
[0xAA][LEN_H][LEN_L][CMD][SUB][DATA...][CHK][0x55] - All values are checked with XOR checksum
- Modbus Function Code is fixed to
0x03currently - Byte order control enables compatibility with big-endian/little-endian devices
🧪 RS-485 Test Area
The Test Area tab is designed for diagnostics and manual communication with Modbus devices. It allows you to send one-off read requests and inspect raw and interpreted results in detail.
📥 Single Request
Enter a one-line configuration string in the same format used in the main configuration panel:
sensor_name,address,register,label,bytes,scaling,offset,orderExample:
LeadMed,1,0x0100,temp,4,1.0,0,ABCDSends Modbus Function 0x03 to slave ID 1
Reads 2 registers (4 bytes)
Applies byte order, scaling, and offset
Shows multiple interpretations
📤 Response Breakdown
The response panel shows:
| Part | Description |
|---|---|
| Raw buffer | The actual byte sequence returned by the sensor |
| Byte order decoding | Value interpreted using various byte orders (ABCD, DCBA, BADC, CDAB) for comparison |
| Raw float | Default float interpretation (usually ABCD) |
| Final Result | The label + scaled value shown using selected order, scaling, and offset |
Request to addr 1, register 0x100, bytes: 4
Raw buffer: 85 12 cd 41
order: ABCD = 25.634043
order: DCBA = -0.000000
order: BADC = -202920224.000000
order: CDAB = 0.000000
Raw float: 25.634043
Final Result: temp:25.63🛠 Debug Passthrough
- Pressing Passthrough activates a transparent debug mode.
- All Modbus communication is sent through as-is without decoding.
- Useful for sniffing, manual commands, or external testing tools.
🔍 Notes
registercan be entered in either hex (with0x) or decimal- Use this tool to validate:
- Correct register mapping
- Proper byte order
- Sensor scaling and offset
- Always match
bytesandorderto your sensor datasheet.