Approximating ambient temperature on the Sense HAT

ApproxTemp shows a well-known trick for the Sense HAT: the two on-board sensors that report temperature (HTS221 and LPS25H) both sit next to the Raspberry Pi's SoC, so they read hotter than the room. This script averages them and subtracts a calibration offset to get a value that is much closer to reality.

Source code: projects/ApproxTemp/ApproxTemp.java

How it works

The getCorrectedTempF method:

1. Reads the temperature from the humidity sensor with hat.getTemperatureFromHumidity().
2. Reads the temperature from the pressure sensor with hat.getTemperatureFromPressure().
3. Averages the two values and subtracts a CALIBRATION_OFFSET_C (defaults to 21.5).
4. Converts the result to Fahrenheit and rounds to one decimal.

The main loop then scrolls a message like 73.4F across the LED matrix every 5 seconds using hat.showMessage(...) in cyan on black.

Tip: the exact calibration value depends on your enclosure, CPU load and whether the Sense HAT is stacked on other HATs. Tune CALIBRATION_OFFSET_C until the reading matches a trusted thermometer.

Running it

This script depends on a specific branch of pi4j-drivers (my igfasouza branch), so clone and install it locally first:

git clone -b igfasouza https://github.com/igfasouza/pi4j-drivers.git
cd pi4j-drivers
mvn install

Then run it with JBang on a Raspberry Pi with a Sense HAT attached:

jbang projects/ApproxTemp/ApproxTemp.java