Sensor
The base class for all sensor implementations.
Sensor
Generic sensor instrument configured with valid tags and namespace.
The Sensor class provides a base for all sensor implementations, handling Modbus RTU communication, tag validation, and dispatch to sensor-specific read functions.
Key Feature: Instruments are created on-demand during read/write operations and immediately cleaned up afterward. This prevents serial port conflicts when multiple sensors share the same physical port.
Parameters:
| Name | Type | Description | Default |
|---|---|---|---|
port
|
str
|
Serial port name (e.g., 'COM3' on Windows, '/dev/ttyUSB0' on Linux). |
required |
valid_tags
|
List[ReadTag]
|
List of ReadTag instances that are valid for this sensor. |
required |
namespace
|
dict
|
Dispatch namespace dictionary containing the multipledispatch Dispatcher for this sensor's tag-specific read functions. |
required |
serial_config_tags
|
Set[ReadTag]
|
Set of tags that configure serial communication (require power cycle). |
None
|
sensor_config_tags
|
Set[ReadTag]
|
Set of tags that configure sensor behavior (may require power cycle). |
None
|
backend_tag
|
ModbusBackendTag
|
Backend tag for dispatch (default: MinimalmodbusBackendTag). |
None
|
slave_address
|
int
|
Modbus slave address (default: 1). |
required |
baudrate
|
int
|
Serial baudrate (default: 19200). |
required |
stopbits
|
Stopbits
|
Number of stop bits (default: Stopbits.ONE). |
required |
bytesize
|
int
|
Number of data bits (default: 8). |
required |
parity
|
Parity
|
Parity setting (default: Parity.NONE). |
required |
modbus_mode
|
ModbusMode
|
Modbus mode (default: ModbusMode.RTU). |
required |
timeout
|
float
|
Serial timeout in seconds (default: 0.5). |
required |
Attributes:
| Name | Type | Description |
|---|---|---|
serial_config_tags |
Set[ReadTag]
|
Tags that configure serial communication settings. |
sensor_config_tags |
Set[ReadTag]
|
Tags that configure sensor behavior settings. |
Notes
Instrument Lifecycle:
Unlike traditional implementations where the instrument is created once in init and persists, this implementation creates the instrument on-demand for each read/write operation:
- User calls read() or write()
- Instrument is created and configured with correct serial settings
- Operation is performed
- Instrument is cleaned up and serial port is closed
- Port is now available for other sensors
This design allows multiple sensors to share the same serial port without conflicts, even if they have different baudrate/stopbit settings.
Performance Impact:
Creating/destroying the instrument adds ~50-100ms overhead per operation. For typical sensor logging intervals (>1s), this is negligible.
Examples:
Multiple sensors on the same port (no conflicts!):
>>> sensor1 = GMP252(port='/dev/ttyACM0', slave_address=121)
>>> sensor2 = AlphaTRACER(port='/dev/ttyACM0', slave_address=122, baudrate=9600)
>>>
>>> # Both work perfectly - no serial port conflicts
>>> result1 = sensor1.read([CO2]) # Creates instrument, reads, cleans up
>>> result2 = sensor2.read([RADON]) # Creates instrument, reads, cleans up
Use with scheduler (original API unchanged):
>>> logger1 = SensorLogger(sensor=sensor1, tags=[CO2], interval_seconds=10, ...)
>>> logger2 = SensorLogger(sensor=sensor2, tags=[RADON], interval_seconds=600, ...)
>>>
>>> scheduler = LoggerScheduler()
>>> scheduler.add_logger(logger1)
>>> scheduler.add_logger(logger2)
>>> scheduler.run() # Just works!
Source code in atmospyre/sensors/sensor.py
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Functions
__init__(port, valid_tags, namespace, slave_address, baudrate, stopbits, bytesize, parity, modbus_mode, timeout, serial_config_tags=None, sensor_config_tags=None, backend_tag=None)
Initialize sensor configuration without creating instrument.
The instrument will be created on-demand during read/write operations.
Source code in atmospyre/sensors/sensor.py
read(tags)
Read one or more measurements using tag dispatch.
Creates an instrument, performs the read operations, then cleans up. The serial port is only held during the actual read operation.
Parameters:
| Name | Type | Description | Default |
|---|---|---|---|
tags
|
ReadTag or List[ReadTag]
|
Single ReadTag instance or list of ReadTag instances to read. All tags must be in the sensor's valid tag list. |
required |
Returns:
| Type | Description |
|---|---|
dict[ReadTag, Any]
|
Dictionary mapping each input tag to its measured value. |
Raises:
| Type | Description |
|---|---|
ValueError
|
If any tag is not in the sensor's valid tag list. |
SensorReadError
|
If reading any tag fails due to communication errors. The exception contains the failed tag and original error. |
Examples:
Single tag read:
Multiple tags:
>>> result = sensor.read([CO2, MEASURED_TEMPERATURE])
>>> print(f"CO2: {result[CO2]}, Temp: {result[MEASURED_TEMPERATURE]}")
CO2: 415.2, Temp: 23.5
Error handling:
>>> try:
... result = sensor.read([CO2, MEASURED_TEMPERATURE])
... except SensorReadError as e:
... print(f"Failed to read {type(e.tag).__name__}")
... print(f"Reason: {e.original_exception}")
Multiple sensors on same port:
>>> sensor1 = GMP252(port='/dev/ttyACM0', slave_address=121)
>>> sensor2 = AlphaTRACER(port='/dev/ttyACM0', slave_address=122)
>>> result1 = sensor1.read([CO2]) # No conflict!
>>> result2 = sensor2.read([RADON]) # No conflict!
Source code in atmospyre/sensors/sensor.py
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write(settings)
Write one or more settings using tag dispatch.
Creates an instrument, performs the write operations, then cleans up. The serial port is only held during the actual write operation.
Parameters:
| Name | Type | Description | Default |
|---|---|---|---|
settings
|
dict[ReadTag, Any]
|
Dictionary mapping tag instances to values to write. |
required |
Raises:
| Type | Description |
|---|---|
ValueError
|
If any tag is not valid for writing. |
Warnings
If writing serial configuration tags, a power cycle is required. Use get_serial_config_tags() to see which tags require power cycle.
Examples:
>>> from atmospyre.sensors.implementations.gmp252 import (
... PRESSURE_COMPENSATION_MODE, CO2_FILTERING_FACTOR
... )
>>> sensor.write({
... PRESSURE_COMPENSATION_MODE: True,
... CO2_FILTERING_FACTOR: 90
... })
>>> # If any serial_config_tags were written, power cycle the sensor
Multiple sensors on same port (no conflicts):
>>> sensor1.write({TAG1: value1}) # Creates instrument, writes, cleans up
>>> sensor2.write({TAG2: value2}) # Creates instrument, writes, cleans up
Source code in atmospyre/sensors/sensor.py
get_valid_tags()
Get list of all valid tags for this sensor.
Returns a copy of the valid tags list to prevent external modification.
Returns:
| Type | Description |
|---|---|
List[ReadTag]
|
Copy of the list of valid ReadTag instances for this sensor. |
Examples:
>>> tags = sensor.get_valid_tags()
>>> print(f"This sensor supports {len(tags)} measurements")
This sensor supports 5 measurements
>>>
>>> for tag in tags:
... meta = tag.metadata
... print(f"- {type(tag).__name__}: {meta.description} ({meta.unit})")
- CO2Tag: CO2 concentration (float) (ppm)
- TemperatureTag: Measurement temperature (°C)
- StatusTag: General device status (None)