4.2.5 RS-485 (Modbus RTU)

Configuration

Serial Configuration

• Baudrate
  • Select the communication speed (bits per second).
  • Must match the baud rate of the connected device (e.g., 9600, 19200, 115200).
• Configuration
  • Defines the serial frame format: data bits, parity, stop bits (e.g., 8N1 = 8 data bits, no parity, 1 stop bit).
  • Ensure this setting matches the external sensor/device.
• Save
  • Stores the selected settings permanently in EEPROM.

RS-485 Sensor Configuration

The Sensor Configuration panel accepts a list of sensors defined in a structured, comma-separated format.

Format

Parameters

• sensor_name → Group name for logs (e.g., SensorName)
• address → Modbus slave ID (decimal, e.g., 1)
• MEAS → Indicator to use trigger so it will not treated as sensor data
• register → Start register address (decimal or hex, e.g., 0 or 0x0000)
• value → value to write(hex, e.g. 0x001F)
• wait → time to wait before next request in ms (decimal 500)
• label → Variable name in the output (e.g., temp, do, do_percent)
• bytes → Number of bytes to read (e.g., 4 for float32 = 2 registers)
• scaling → Multiplier for raw value (e.g., 1.0, 0.01)
• offset → Value added after scaling (e.g., 0)
• order → Byte order for decoding (ABCD, DCBA, BADC, CDAB)
• function → can be left blank for request with Function code 03, add 1 for request with function code 04 instead

Example Entries

SensorName,1,MEAS,0x0001,0x001F,500
SensorName,1,0,temp,4,1.0,0,ABCD
SensorName,1,290,do,4,1.0,0,ABCD,1
SensorName,1,292,do_percent,4,1.0,0,ABCD

Save & Load

• Save → Stores the current configuration.
• Load → Loads a previously saved configuration file.

Live Reading

• When Live Reading = ON, the SmartSampler polls all configured Modbus sensors in sequence.
• Each request is built using the Device ID and Register Address.
• Responses are decoded according to the configured byte order, scaling, and offset.
• Results appear in the Live Reading panel with timestamps.