API Reference

Svm40I2cDevice

class sensirion_i2c_svm40.device.Svm40I2cDevice(connection, slave_address=106)

SVM40 I²C device class to allow executing I²C commands.

__init__(connection, slave_address=106)

Constructs a new SVM40 I²C device.

Parameters:

• connection (I2cConnection) – The I²C connection to use for communication.
• slave_address (byte) – The I²C slave address, defaults to 0x6A.

device_reset()

Execute a device reset (reboot firmware, similar to power cycle).

get_serial_number()

Get the serial number of the device.

Returns:The serial number as a hex formatted ASCII string. Return type:string

get_version()

Get the version of the device firmware, hardware and SHDLC protocol.

Returns:The device version. Return type:Version

get_compensation_temperature_offset()

Gets the temperature offset for RHT measurements.

Returns:Temperature offset in degrees celsius. Return type:float

set_compensation_temperature_offset(t_offset)

Sets the temperature offset for RHT measurements.

Note

Execute the command store_nv_data() command after writing the parameter to store it in the non-volatile memory of the device otherwise the parameter will be reset upton a device reset.

Parameters:t_offset (float) – Temperature offset in degrees celsius.

get_voc_tuning_parameters()

Gets the currently set parameters for customizing the VOC algorithm.

Returns:

• voc_index_offset (int) - VOC index representing typical (average) conditions. The default value is 100.
• learning_time_hours (int) - Time constant of long-term estimator in hours. Past events will be forgotten after about twice the learning time. The default value is 12 hours.
• gating_max_duration_minutes (int) - Maximum duration of gating in minutes (freeze of estimator during high VOC index signal). Zero disables the gating. The default value is 180 minutes.
• std_initial (int) - Initial estimate for standard deviation. Lower value boosts events during initial learning period, but may result in larger device-to-device variations. The default value is 50.

Return type:tuple

set_voc_tuning_parameters(voc_index_offset, learning_time_hours, gating_max_duration_minutes, std_initial)

Sets parameters to customize the VOC algorithm. This command is only available in idle mode.

Note

Execute the command store_nv_data() after writing the parameter to store it in the non-volatile memory of the device otherwise the parameter will be reset upton a device reset.

Parameters:

• voc_index_offset (int) – VOC index representing typical (average) conditions. The default value is 100.
• learning_time_hours (int) – Time constant of long-term estimator in hours. Past events will be forgotten after about twice the learning time. The default value is 12 hours.
• gating_max_duration_minutes (int) – Maximum duration of gating in minutes (freeze of estimator during high VOC index signal). Set to zero to disable the gating. The default value is 180 minutes.
• std_initial (int) – Initial estimate for standard deviation. Lower value boosts events during initial learning period, but may result in larger device-to-device variations. The default value is 50.

store_nv_data()

Stores all customer engine parameters to the non-volatile memory.

get_voc_state()

Gets the current VOC algorithm state. Retrieved values can be used to set the VOC algorithm state to resume operation after a short interruption, skipping initial learning phase. This command is only available during measurement mode.

Note

This feature can only be used after at least 3 hours of continuous operation.

Returns:Current VOC algorithm state. Return type:list(int)

set_voc_state(state)

Set previously retrieved VOC algorithm state to resume operation after a short interruption, skipping initial learning phase. This command is only available in idle mode.

Note

This feature should not be used after interruptions of more than 10 minutes.

Parameters:state (list(int)) – Current VOC algorithm state.

start_measurement()

Starts continuous measurement in polling mode.

Note

This command is only available in idle mode.

stop_measurement()

Leaves the measurement mode and returns to the idle mode.

Note

This command is only available in measurement mode.

read_measured_values()

Returns the new measurement results.

Note

This command is only available in measurement mode. The firmware updates the measurement values every second. Polling data with a faster sampling rate will return the same values. The first measurement is available 1 second after the start measurement command is issued. Any readout prior to this will return zero initialized values.

Returns:The measured air quality, humidity and temperature.

• air_quality (AirQuality) - Air quality response object.
• humidity (Humidity) - Humidity response object.
• temperature (Temperature) - Temperature response object.

Return type:tuple

read_measured_values_raw()

Returns the new measurement results with raw values added.

Note

This command is only available in measurement mode. The firmware updates the measurement values every second. Polling data with a faster sampling rate will return the same values. The first measurement is available 1 second after the start measurement command is issued. Any readout prior to this will return zero initialized values.

Returns:The measured air quality, humidity and temperature including the raw values without algorithm compensation.

• air_quality (AirQuality) - Air quality response object.
• humidity (Humidity) - Humidity response object.
• temperature (Temperature) - Temperature response object.
• raw_voc_ticks (int) - Raw VOC output ticks as read from the SGP sensor.
• raw_humidity (Humidity) - Humidity response object.
• raw_temperature (Temperature) - Temperature response object.

Return type:tuple

connection

Get the used I²C connection.

Returns:The used I²C connection. Return type:I2cConnection

execute(command)

Execute an I²C command on this device.

Parameters:command (I2cCommand) – The command to be executed. Returns:The interpreted response of the executed command. Return type:Depends on the executed command.

slave_address

Get the I²C slave address.

Returns:The I²C slave address. Return type:byte

Response Data Types

Air Quality

class sensirion_i2c_svm40.response_types.AirQuality(ticks)

Represents a measurement response for the air quality.

With the ticks you can access the raw data as received from the device. For the converted value the voc_index attribute is available.

__init__(ticks)

Creates an instance from the received raw data.

Parameters:ticks (int) – The read ticks as received from the device.

ticks

The ticks (int) as received from the device.

voc_index

The converted VOC index.

Humidity

class sensirion_i2c_svm40.response_types.Humidity(ticks)

Represents a measurement response for the humidity.

With the ticks you can access the raw data as received from the device. For the converted value the percent_rh attribute is available.

__init__(ticks)

Creates an instance from the received raw data.

Parameters:ticks (int) – The read ticks as received from the device.

ticks

The ticks (int) as received from the device.

percent_rh

The converted humidity in %RH.

Temperature

class sensirion_i2c_svm40.response_types.Temperature(ticks)

Represents a measurement response for the temperature.

With the ticks you can access the raw data as received from the device. For the converted values you can choose between degrees_celsius and degrees_fahrenheit.

__init__(ticks)

Creates an instance from the received raw data.

Parameters:ticks (int) – The read ticks as received from the device.

ticks

The ticks (int) as received from the device.

degrees_celsius

The converted temperature in °C.

degrees_fahrenheit

The converted temperature in °F.

Version

class sensirion_i2c_svm40.version_types.FirmwareVersion(major, minor, debug)

Class representing the firmware version of a device.

__init__(major, minor, debug)

Constructor.

Parameters:

• major (byte) – Major version (0..255).
• minor (byte) – Minor version (0..99).
• debug (bool) – Debug flag (False for official releases).

class sensirion_i2c_svm40.version_types.HardwareVersion(major, minor)

Class representing the hardware version of a device.

__init__(major, minor)

Constructor.

Parameters:

• major (byte) – Major version (0..255).
• minor (byte) – Minor version (0..99).

class sensirion_i2c_svm40.version_types.ProtocolVersion(major, minor)

Class representing the I2C protocol version of an I2C device.

__init__(major, minor)

Constructor.

Parameters:

• major (byte) – Major version (0..255).
• minor (byte) – Minor version (0..99).

class sensirion_i2c_svm40.version_types.Version(firmware, hardware, protocol)

Class representing all version numbers of an I2C device. This is used for the “Get Version” command.

__init__(firmware, hardware, protocol)

Constructor.

Parameters:

• firmware (FirmwareVersion) – Firmware version.
• hardware (HardwareVersion) – Hardware version.
• protocol (ProtocolVersion) – SHDLC protocol version.

Commands

class sensirion_i2c_svm40.commands.generated.Svm40I2cCmdGetSerialNumber

Get Serial Number I²C Command

Gets the serial number from the device.

__init__()

Constructor.

interpret_response(data)

Validates the CRCs of the received data from the device and returns the interpreted data.

Parameters:data (bytes) – Received raw bytes from the read operation. Returns:Ascii string containing the serial number. The string has the null-termination character included. Return type:str Raises:I2cChecksumError – If a received CRC was wrong.

class sensirion_i2c_svm40.commands.generated.Svm40I2cCmdDeviceReset

Device Reset I²C Command

Executs a reset on the device.

Note

The device will reply before executing the reset.

__init__()

Constructor.

interpret_response(data)

Validates the CRCs of the received data from the device and returns the data with all CRCs removed.

Parameters:data (bytes) – Received raw bytes from the read operation. Returns:The received bytes, or None if there is no data received. Return type:bytes or None Raises:I2cChecksumError – If a received CRC was wrong.

class sensirion_i2c_svm40.commands.generated.Svm40I2cCmdStartContinuousMeasurement

Start Continuous Measurement I²C Command

Starts continuous measurement in polling mode.

Note

This command is only available in idle mode.

__init__()

Constructor.

interpret_response(data)

Validates the CRCs of the received data from the device and returns the data with all CRCs removed.

Parameters:data (bytes) – Received raw bytes from the read operation. Returns:The received bytes, or None if there is no data received. Return type:bytes or None Raises:I2cChecksumError – If a received CRC was wrong.

class sensirion_i2c_svm40.commands.generated.Svm40I2cCmdStopMeasurement

Stop Measurement I²C Command

Stops the measurement mode and returns to idle mode.

Note

This command is only available in measurement mode.

__init__()

Constructor.

interpret_response(data)

Validates the CRCs of the received data from the device and returns the data with all CRCs removed.

Parameters:data (bytes) – Received raw bytes from the read operation. Returns:The received bytes, or None if there is no data received. Return type:bytes or None Raises:I2cChecksumError – If a received CRC was wrong.

class sensirion_i2c_svm40.commands.generated.Svm40I2cCmdGetVocAlgorithmTuningParameters

Get Voc Algorithm Tuning Parameters I²C Command

Gets the currently set parameters for customizing the VOC algorithm

__init__()

Constructor.

interpret_response(data)

Validates the CRCs of the received data from the device and returns the interpreted data.

Parameters:data (bytes) – Received raw bytes from the read operation. Returns:

• voc_index_offset (int) - VOC index representing typical (average) conditions. The default value is 100.
• learning_time_hours (int) - Time constant of long-term estimator in hours. Past events will be forgotten after about twice the learning time. The default value is 12 hours.
• gating_max_duration_minutes (int) - Maximum duration of gating in minutes (freeze of estimator during high VOC index signal). Zero disables the gating. The default value is 180 minutes.
• std_initial (int) - Initial estimate for standard deviation. Lower value boosts events during initial learning period, but may result in larger device-to-device variations. The default value is 50.

Return type:tuple Raises:I2cChecksumError – If a received CRC was wrong.

class sensirion_i2c_svm40.commands.generated.Svm40I2cCmdSetVocAlgorithmTuningParameters(voc_index_offset, learning_time_hours, gating_max_duration_minutes, std_initial)

Set Voc Algorithm Tuning Parameters I²C Command

Sets the parameters to customize the VOC algorithm. This command is only available in idle mode.

__init__(voc_index_offset, learning_time_hours, gating_max_duration_minutes, std_initial)

Constructor.

Parameters:

• voc_index_offset (int) – VOC index representing typical (average) conditions. The default value is 100.
• learning_time_hours (int) – Time constant of long-term estimator in hours. Past events will be forgotten after about twice the learning time. The default value is 12 hours.
• gating_max_duration_minutes (int) – Maximum duration of gating in minutes (freeze of estimator during high VOC index signal). Set to zero to disable the gating. The default value is 180 minutes.
• std_initial (int) – Initial estimate for standard deviation. Lower value boosts events during initial learning period, but may result in larger device-to-device variations. The default value is 50.

interpret_response(data)

Validates the CRCs of the received data from the device and returns the data with all CRCs removed.

Parameters:data (bytes) – Received raw bytes from the read operation. Returns:The received bytes, or None if there is no data received. Return type:bytes or None Raises:I2cChecksumError – If a received CRC was wrong.

class sensirion_i2c_svm40.commands.generated.Svm40I2cCmdGetVocAlgorithmState

Get Voc Algorithm State I²C Command

Gets the current VOC algorithm state.

__init__()

Constructor.

interpret_response(data)

Validates the CRCs of the received data from the device and returns the interpreted data.

Parameters:data (bytes) – Received raw bytes from the read operation. Returns:Current VOC algorithm state. Return type:list(int) Raises:I2cChecksumError – If a received CRC was wrong.

class sensirion_i2c_svm40.commands.generated.Svm40I2cCmdSetVocAlgorithmState(state)

Set Voc Algorithm State I²C Command

Sets the VOC algorithm state. This command is only available in idle mode.

__init__(state)

Constructor.

Parameters:state (list(int)) – Current VOC algorithm state.

interpret_response(data)

Validates the CRCs of the received data from the device and returns the data with all CRCs removed.

Parameters:data (bytes) – Received raw bytes from the read operation. Returns:The received bytes, or None if there is no data received. Return type:bytes or None Raises:I2cChecksumError – If a received CRC was wrong.

class sensirion_i2c_svm40.commands.generated.Svm40I2cCmdStoreNvData

Store Nv Data I²C Command

Stores all algorithm parameters to the non-volatile memory.

__init__()

Constructor.

interpret_response(data)

Validates the CRCs of the received data from the device and returns the data with all CRCs removed.

Parameters:data (bytes) – Received raw bytes from the read operation. Returns:The received bytes, or None if there is no data received. Return type:bytes or None Raises:I2cChecksumError – If a received CRC was wrong.

class sensirion_i2c_svm40.commands.wrapped.Svm40I2cCmdGetVersion

Get Version I²C Command

Gets the version information for the hardware, firmware and protocol.

__init__()

Constructor.

interpret_response(data)

Validates the CRCs of the received data from the device and returns the interpreted data.

Parameters:data (bytes) – Received raw bytes from the read operation. Returns:The device version as a Version object. Return type:Version Raises:I2cChecksumError – If a received CRC was wrong.

class sensirion_i2c_svm40.commands.wrapped.Svm40I2cCmdReadMeasuredValues

Returns the new measurement results.

Note

This command is only available in measurement mode. The firmware updates the measurement values every second. Polling data with a faster sampling rate will return the same values. The first measurement is available 1 second after the start measurement command is issued. Any readout prior to this will return zero initialized values.

__init__()

Constructor.

interpret_response(data)

Validates the CRCs of the received data from the device and returns the interpreted data.

Parameters:data (bytes) – Received raw bytes from the read operation. Returns:The measured air quality, humidity and temperature.

• air_quality (AirQuality) - Air quality response object.
• humidity (Humidity) - Humidity response object.
• temperature (Temperature) - Temperature response object.

Return type:tuple Raises:I2cChecksumError – If a received CRC was wrong.

class sensirion_i2c_svm40.commands.wrapped.Svm40I2cCmdReadMeasuredValuesRaw

Returns the new measurement results with raw values added.

Note

This command is only available in measurement mode. The firmware updates the measurement values every second. Polling data with a faster sampling rate will return the same values. The first measurement is available 1 second after the start measurement command is issued. Any readout prior to this will return zero initialized values.

__init__()

Constructor.

interpret_response(data)

Validates the CRCs of the received data from the device and returns the interpreted data.

Parameters:data (bytes) – Received raw bytes from the read operation. Returns:The measured air quality, humidity and temperature including the raw values without algorithm compensation.

• air_quality (AirQuality) - Air quality response object.
• humidity (Humidity) - Humidity response object.
• temperature (Temperature) - Temperature response object.
• raw_voc_ticks (int) - Raw VOC output ticks as read from the SGP sensor.
• raw_humidity (Humidity) - Humidity response object.
• raw_temperature (Temperature) - Temperature response object.

Return type:tuple Raises:I2cChecksumError – If a received CRC was wrong.

class sensirion_i2c_svm40.commands.wrapped.Svm40I2cCmdGetTemperatureOffsetForRhtMeasurements

Get Temperature Offset For Rht Measurements I²C Command

Gets the T-Offset for the temperature compensation of the RHT algorithm.

__init__()

Constructor.

interpret_response(data)

Validates the CRCs of the received data from the device and returns the interpreted data.

Parameters:data (bytes) – Received raw bytes from the read operation. Returns:Temperature offset in degrees celsius. Return type:float Raises:I2cChecksumError – If a received CRC was wrong.

class sensirion_i2c_svm40.commands.wrapped.Svm40I2cCmdSetTemperatureOffsetForRhtMeasurements(t_offset)

Set Temperature Offset For Rht Measurements I²C Command

Sets the T-Offset for the temperature compensation of the RHT algorithm.

__init__(t_offset)

Constructor.

Parameters:t_offset (float) – Temperature offset in degrees celsius.

interpret_response(data)

Validates the CRCs of the received data from the device and returns the data with all CRCs removed.

Parameters:data (bytes) – Received raw bytes from the read operation. Returns:The received bytes, or None if there is no data received. Return type:bytes or None Raises:I2cChecksumError – If a received CRC was wrong.