minimal_example.py
"""Minimal ModbusDevice example: read and write against the sim server.
Start the sim server first:
python -m instro.modbus.sim_server
Then in another shell:
python examples/modbus/minimal_example.py
"""
from pathlib import Path
from instro.modbus import ModbusDevice
CONFIG_PATH = Path(__file__).parent / "simulated_modbus_device.json"
CONNECTION = {"transport": "tcp", "host": "127.0.0.1", "port": 5020}
def main() -> None:
device = ModbusDevice(config=CONFIG_PATH, connection=CONNECTION)
with device:
# Read a holding register (float32 temperature, seeded to 72.5 in the sim).
m = device.read("temperature")
print(f"temperature: {m.latest}")
# Write a holding register. `setpoint` declares a linear scale (gain=0.1),
# so we pass the physical value. The driver converts to raw internally.
device.write("setpoint", 30.0)
# Read back to confirm the write landed.
m = device.read("setpoint")
print(f"setpoint (after write): {m.latest}")
if __name__ == "__main__":
main()