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feat: Add Slave ID support for Modbus TCP master plugin #79

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Merged
thiagoralves merged 2 commits into from
Jan 19, 2026
Merged

feat: Add Slave ID support for Modbus TCP master plugin #79

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189cdb8
feat: Add Slave ID support for Modbus TCP master plugin
thiagoralves Jan 19, 2026
afede96
fix: Use device_id parameter for pymodbus 3.10+
thiagoralves Jan 19, 2026
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3 changes: 2 additions & 1 deletion core/src/drivers/plugins/python/modbus_master/modbus_master_connection.py
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Original file line number Diff line number Diff line change
Expand Up @@ -9,10 +9,11 @@
class ModbusConnectionManager: # pylint: disable=too-many-instance-attributes
"""Manages Modbus TCP connections with retry logic."""

def __init__(self, host: str, port: int, timeout_ms: int):
def __init__(self, host: str, port: int, timeout_ms: int, slave_id: int = 1):
self.host = host
self.port = port
self.timeout = timeout_ms / 1000.0 # Convert to seconds
self.slave_id = slave_id # Unit/Slave ID for Modbus TCP gateways

# Retry configuration
self.retry_delay_base = 2.0 # initial delay between attempts (seconds)
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23 changes: 13 additions & 10 deletions core/src/drivers/plugins/python/modbus_master/modbus_master_plugin.py
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Original file line number Diff line number Diff line change
Expand Up @@ -74,7 +74,7 @@ def __init__(self, device_config: Any, sba: SafeBufferAccess, plugin_logger: Plu
self.logger = plugin_logger
self._stop_event = threading.Event()
self.connection_manager = ModbusConnectionManager(
device_config.host, device_config.port, device_config.timeout_ms
device_config.host, device_config.port, device_config.timeout_ms, device_config.slave_id
)
self.name = f"ModbusSlave-{device_config.name}-{device_config.host}:{device_config.port}"

Expand Down Expand Up @@ -149,22 +149,23 @@ def run(self): # pylint: disable=too-many-locals
count = point.length # 1:1 mapping for boolean operations

# Perform Modbus read based on function code
# Note: pymodbus 3.x requires count as keyword argument
# Note: pymodbus 3.10+ uses device_id parameter (formerly slave)
# device_id is used for Modbus TCP gateways that forward to RS485 devices
if point.fc == 1: # Read Coils
response = self.connection_manager.client.read_coils(
address, count=count
address, count=count, device_id=self.connection_manager.slave_id
)
elif point.fc == 2: # Read Discrete Inputs
response = self.connection_manager.client.read_discrete_inputs(
address, count=count
address, count=count, device_id=self.connection_manager.slave_id
)
elif point.fc == 3: # Read Holding Registers
response = self.connection_manager.client.read_holding_registers(
address, count=count
address, count=count, device_id=self.connection_manager.slave_id
)
elif point.fc == 4: # Read Input Registers
response = self.connection_manager.client.read_input_registers(
address, count=count
address, count=count, device_id=self.connection_manager.slave_id
)
else:
self.logger.warn(f"[{self.name}] Unsupported read FC: {point.fc}")
Expand Down Expand Up @@ -327,10 +328,12 @@ def run(self): # pylint: disable=too-many-locals
continue

# Perform Modbus write operation
# Note: pymodbus 3.10+ uses device_id parameter (formerly slave)
# device_id is used for Modbus TCP gateways that forward to RS485 devices
if point.fc == 5: # Write Single Coil
if len(values_to_write) > 0:
response = self.connection_manager.client.write_coil(
address, values_to_write[0]
address, values_to_write[0], device_id=self.connection_manager.slave_id
)
else:
self.logger.error(
Expand All @@ -341,7 +344,7 @@ def run(self): # pylint: disable=too-many-locals
elif point.fc == 6: # Write Single Register
if len(values_to_write) > 0:
response = self.connection_manager.client.write_register(
address, values_to_write[0]
address, values_to_write[0], device_id=self.connection_manager.slave_id
)
else:
self.logger.error(
Expand All @@ -351,11 +354,11 @@ def run(self): # pylint: disable=too-many-locals
continue
elif point.fc == 15: # Write Multiple Coils
response = self.connection_manager.client.write_coils(
address, values_to_write
address, values_to_write, device_id=self.connection_manager.slave_id
)
elif point.fc == 16: # Write Multiple Registers
response = self.connection_manager.client.write_registers(
address, values_to_write
address, values_to_write, device_id=self.connection_manager.slave_id
)
else:
self.logger.warn(f"[{self.name}] Unsupported write FC: {point.fc}")
Expand Down
6 changes: 5 additions & 1 deletion core/src/drivers/plugins/python/shared/plugin_config_decode/modbus_master_config_model.py
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Original file line number Diff line number Diff line change
Expand Up @@ -73,6 +73,7 @@ def __init__(self):
self.host: str = "127.0.0.1"
self.port: int = 502
self.timeout_ms: int = 1000
self.slave_id: int = 1 # Unit/Slave ID for Modbus TCP gateways (0-255)
self.io_points: List['ModbusIoPointConfig'] = []

@classmethod
Expand All @@ -89,6 +90,7 @@ def from_dict(cls, data: Dict[str, Any]) -> 'ModbusDeviceConfig':
device.host = config.get("host", "127.0.0.1")
device.port = config.get("port", 502)
device.timeout_ms = config.get("timeout_ms", 1000)
device.slave_id = config.get("slave_id", 1)

# Parse I/O points
io_points_data = config.get("io_points", [])
Expand All @@ -110,6 +112,8 @@ def validate(self) -> None:
raise ValueError(f"Invalid port: {self.port}. Must be a positive integer for device {self.name}.")
if not isinstance(self.timeout_ms, int) or self.timeout_ms <= 0:
raise ValueError(f"Invalid timeout_ms: {self.timeout_ms}. Must be a positive integer for device {self.name}.")
if not isinstance(self.slave_id, int) or not (0 <= self.slave_id <= 255):
raise ValueError(f"Invalid slave_id: {self.slave_id}. Must be an integer between 0 and 255 for device {self.name}.")

for i, point in enumerate(self.io_points):
if not isinstance(point, ModbusIoPointConfig):
Expand All @@ -126,7 +130,7 @@ def validate(self) -> None:
raise ValueError(f"Invalid cycle_time_ms: {point.cycle_time_ms}. Must be a positive integer for device {self.name}, point {i}.")

def __repr__(self) -> str:
return f"ModbusDeviceConfig(name='{self.name}', host='{self.host}', port={self.port}, io_points={len(self.io_points)})"
return f"ModbusDeviceConfig(name='{self.name}', host='{self.host}', port={self.port}, slave_id={self.slave_id}, io_points={len(self.io_points)})"

class ModbusMasterConfig(PluginConfigContract):
"""
Expand Down