Weatherstation Modbus Register 15: Längengrad

Technical Definition

The register Längengrad at address 15 is used to monitor längengrad on the Weatherstation.

• Protocol: Modbus RTU
• Data Type: S WORD
• Unit: °
• Access: Read Only

How to Read (Python pymodbus)

Use this code snippet to read this specific value via RS485:

from pymodbus.client.sync import ModbusSerialClient

client = ModbusSerialClient(method='rtu', port='/dev/ttyUSB0', baudrate=9600)
client.connect()

# Read Längengrad (Address: 15)
# Note: Check if your device uses 0-based or 1-based addressing
result = client.read_input_registers(address=15, count=2, unit=1)

if not result.isError():
    print(f"Raw Value: {result.registers}")
else:
    print("Error reading register")

client.close()

Integration (Home Assistant)

Paste this into your configuration.yaml:

- platform: modbus_controller
  name: "Längengrad"
  address: 15
  value_type: S_WORD
  unit_of_measurement: "°"

Connection Diagram

Here is the standard RS485 wiring for this configuration:

graph TD
    PLC[Host Controller / Home Assistant]
    Device[Weatherstation]

    PLC -- "A+ (D+)" --> Device
    PLC -- "B- (D-)" --> Device
    PLC -- GND --> Device

💡 Engineer's Insight

Analysis: Geographical longitude (degrees). Specifies the east-west position on Earth. Essential for accurate location-based calculations and mapping.

Troubleshooting: Incorrect or zero values suggest GPS issues, antenna problems, or lack of satellite lock. Verify GPS signal strength and antenna connection.