13. API - Environment Sensors

The Sense HAT has two environment sensors: a humidity sensor and a pressure sensor, which are exposed in the combined SenseEnviron class. This provides readings as EnvironReadings tuples.

13.1. SenseEnviron

class pisense.SenseEnviron(settings=None, temp_source=<function temp_humidity>, emulate=False)[source]

The SenseEnviron class represents the suite of environmental sensors on the Sense HAT. Users can either instantiate this class themselves, or can access an instance from SenseHAT.environ.

The temperature, pressure, and humidity attributes can be queried to read the current values from the sensors. Alternatively, the instance can be treated as an iterator in which case readings will be yielded as they are detected:

hat = SenseHAT()
for reading in hat.environ:
    print(reading.temperature)

Because both the pressure and humidity sensors contain a temperature sensor, a source must be selected for the temperature reading. By default this is from the pressure sensor only, but you can specify a function for temperature_source which, given the two temperature readings returns the reading you are interested in, or some combination there-of.

The settings parameter can be used to point to alternate settings files. The temp_source parameter provides an initial value for the temp_source attribute (this defaults to temp_humidity()). If the emulate parameter is True, the instance will connect to the environment sensors in the desktop Sense HAT emulator instead of the “real” Sense HAT’s sensors.

close()[source]

Call the close() method to close the environmental sensor interface and free up any background resources. The method is idempotent (you can call it multiple times without error) and after it is called, any operations on the environmental sensors may return an error (but are not guaranteed to do so).

read()[source]

Return the current state of all environmental sensors as an EnvironReadings tuple.

Note

This method will wait until the next set of readings are available, and then return them. Hence it is suitable for use in a loop without additional waits, although it may be simpler to simply treat the instance as an iterator in that case.

This is in contrast to reading the pressure, humidity, and temperature attributes which always return immediately.

humidity

Return the current humidity reading from the environmental sensors. The humidity is measured as a % of relative humidity.

pressure

Return the current pressure reading from the environmental sensors. The pressure is measured in millibars (aka hectopascals).

temp_source

Specify the conversion function for the temperature sensors.

The Sense HAT contains two temperature sensors, one in the humidity sensor, and one in the pressure sensor. The temp_source property contains the function that is used to determine how the temperature is reported from the two sources. The function must take two parameters (the readings from the humidity and pressure sensors respectively) and can return whatever you wish to see as the value of the temperature property (including a tuple of both temperatures).

The default value is temp_humidity() which simply returns the reading from the humidity sensor, discarding the the pressure sensor reading.

Warning

You may be tempted to average the two readings under the assumption that this will provide more accuracy. This is almost certainly not the case!

temperature

Return the current temperature reading from the environment sensors. The temperature is measured in degrees celsius.

13.2. EnvironReadings

class pisense.EnvironReadings(pressure, humidity, temperature)[source]

A namedtuple() representing the readings from the environmental sensors as a named 3-tuple containing the fields pressure (in mbar or hPa), humidity (in %RH), and temperature (in °C) respectively.

13.3. Temperature Configuration

pisense.temp_pressure(p_temp, h_temp)[source]

Use this function as temp_source if you want to read temperature from the pressure sensor only. This is the default.

pisense.temp_humidity(p_temp, h_temp)[source]

Use this function as temp_source if you want to read temperature from the humidity sensor only.

pisense.temp_average(p_temp, h_temp)[source]

Use this function as temp_source if you wish to read the average of both the pressure and humidity sensor’s temperatures.

pisense.temp_both(p_temp, h_temp)[source]

Use this function as temp_source if you wish to return both the pressure and humidity sensor’s temperature readings as a tuple from the temperature attribute.