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zltech_modbus.py

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+"""pymodbus-based helpers for the ZLAC8015D V4 RS485 (Modbus RTU) protocol.
+
+Register reference (from "ZLAC8015D V4 Series RS485 Communication" manual):
+  0x2001  RS485 Custom Drive Node Number   (RW/S, range 1-127, default 1)
+  0x2002  RS485 custom communication baud rate (RW/S)
+  0x2010  Save all RW attribute parameters to EEPROM (write 1 to save)
+
+Requires: pip install pymodbus pyserial
+"""
+from pymodbus.client import ModbusSerialClient
+
+REG_NODE_ID = 0x2001
+REG_SAVE_EEPROM = 0x2010
+
+# pymodbus renamed the "slave id" keyword across major versions
+# (unit -> slave -> device_id). Try each so this works regardless of
+# which pymodbus version is installed (e.g. on the Ubuntu test box).
+_ID_KWARGS = ("device_id", "slave", "unit")
+
+
+def _call(fn, *args, node_id, **kwargs):
+    last_err = None
+    for kw in _ID_KWARGS:
+        try:
+            return fn(*args, **{kw: node_id}, **kwargs)
+        except TypeError as exc:
+            last_err = exc
+            continue
+    raise TypeError(f"pymodbus client does not accept any of {_ID_KWARGS}: {last_err}")
+
+
+def make_client(port: str, baud: int = 115200, timeout: float = 0.3) -> ModbusSerialClient:
+    return ModbusSerialClient(
+        port,
+        baudrate=baud,
+        bytesize=8,
+        parity="N",
+        stopbits=1,
+        timeout=timeout,
+    )
+
+
+def read_register(client: ModbusSerialClient, node_id: int, address: int, count: int = 1):
+    """Return list of register values, or None on error/no response."""
+    result = _call(client.read_holding_registers, address, node_id=node_id, count=count)
+    if result is None or result.isError():
+        return None
+    return result.registers
+
+
+def write_register(client: ModbusSerialClient, node_id: int, address: int, value: int) -> bool:
+    result = _call(client.write_register, address, value, node_id=node_id)
+    if result is None or result.isError():
+        return False
+    return True