fix: fix data acquisition from SHT21 temperature and humidity sensor

[marcnause]

Part of #2773

The fixed code can be used as a template for the Flutter version of the app.

Changes

• Fixed problems in sensor data acquisition
• Some minor refactoring and code cleanup

Screenshots / Recordings

Screen_recording_20250706_184339.mp4

Checklist:

• No hard coding: I have used resources from strings.xml, dimens.xml and colors.xml without hard coding any value.
• No end of file edits: No modifications done at end of resource files strings.xml, dimens.xml or colors.xml.
• Code reformatting: I have reformatted code and fixed indentation in every file included in this pull request.
• No extra space: My code does not contain any extra lines or extra spaces than the ones that are necessary.

Summary by Sourcery

Fix SHT21 sensor data acquisition by correcting register addresses, conversion formulas, and checksum handling; refactor measurement API to use an enum; and improve logging, buffer management, and error handling across sensor and communication modules.

Bug Fixes:

• Correct I2C register addresses, timing delays, raw-to-physical conversion formulas, and checksum logic for accurate SHT21 readings.
• Handle empty or invalid sensor data by returning null on failures and logging appropriate error messages.

Enhancements:

• Introduce a Mode enum and setMode method for selecting temperature or humidity measurements.
• Simplify getRaw() to return a single Double value and streamline data handling in SensorSHT21 and UI fragments.
• Clean up CommunicationHandler by removing unused fields, consolidating buffers, and updating logging with class-based TAGs.
• Replace printStackTrace calls with structured Log statements across fragment and activity classes.

Documentation:

• Add Javadoc for the I2C.readBulk method to document its parameters and behavior.

[sourcery-ai]

Reviewer's Guide

This PR refactors the SHT21 sensor acquisition pipeline by introducing an enum-based mode API, static and concise data‐conversion methods with robust checksum/error handling, updates dependent data‐fetch and UI code to the new API, and cleans up logging, unused fields, and adds documentation for I2C.readBulk.

Sequence diagram for SHT21 sensor data acquisition with new enum-based API

sequenceDiagram
    participant SensorSHT21 as SensorSHT21.SensorDataFetch
    participant SHT21 as SHT21
    participant I2C as I2C
    SensorSHT21->>SHT21: setMode(Mode.TEMPERATURE)
    SensorSHT21->>SHT21: getRaw()
    SHT21->>I2C: writeBulk(ADDRESS, [registerAddress])
    SHT21->>I2C: readBulk(ADDRESS, registerAddress, 3)
    I2C-->>SHT21: List<Integer> vals
    SHT21->>SHT21: calculateChecksum(vals, 2)
    SHT21->>SHT21: rawToTemp(vals)
    SHT21-->>SensorSHT21: Double temperature
    SensorSHT21->>SHT21: setMode(Mode.HUMIDITY)
    SensorSHT21->>SHT21: getRaw()
    SHT21->>I2C: writeBulk(ADDRESS, [registerAddress])
    SHT21->>I2C: readBulk(ADDRESS, registerAddress, 3)
    I2C-->>SHT21: List<Integer> vals
    SHT21->>SHT21: calculateChecksum(vals, 2)
    SHT21->>SHT21: rawToRH(vals)
    SHT21-->>SensorSHT21: Double humidity

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Class diagram for SensorSHT21.SensorDataFetch data handling changes

classDiagram
    class SensorSHT21.SensorDataFetch {
        -Double dataSHT21Temp
        -Double dataSHT21Humidity
        -float timeElapsed
        +boolean getSensorData()
        +void updateUi()
    }
    SensorSHT21.SensorDataFetch --> SHT21

Loading

Class diagram for I2C readBulk method addition

classDiagram
    class I2C {
        +ArrayList<Integer> readBulk(int deviceAddress, int registerAddress, int bytesToRead)
    }

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File-Level Changes

Change	Details	Files
Refactor SHT21 sensor communication and data conversion	Introduce Mode enum with registerAddress for temperature/humidity Replace mutable constants with static final fields Convert rawToTemp/rawToRH to static methods returning Double Enhance getRaw to use readBulk, handle empty data and checksum errors	app/src/main/java/io/pslab/communication/sensors/SHT21.java
Update SensorDataFetch to use new SHT21 API and simplify data storage	Replace List buffers with single Double fields Use setMode and getRaw returning Double instead of selectParameter and List Adjust chart entries and UI updates to use primitive float values	app/src/main/java/io/pslab/sensors/SensorSHT21.java
Enhance ThermometerDataFragment parameter parsing and logging	Remove hardcoded TEMPERATURE string and use TAG constant Switch from Integer.valueOf to Integer.parseInt for sensorType Replace e.printStackTrace with Log.e Use setMode(Enum) when initiating SHT21	app/src/main/java/io/pslab/fragment/ThermometerDataFragment.java
Clean up CommunicationHandler internals and logging	Remove unused mWriteBuffer and drivers field Localize drivers list variable Standardize Log.v calls to use TAG	app/src/main/java/io/pslab/communication/CommunicationHandler.java
Document I2C.readBulk and improve exception logging in SensorActivity	Add Javadoc for readBulk documenting parameters and return Replace printStackTrace in SensorActivity with Log.w for sensor scanning errors	app/src/main/java/io/pslab/communication/peripherals/I2C.java app/src/main/java/io/pslab/activity/SensorActivity.java

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[github-actions]

Build successful. APKs to test: https://github.com/fossasia/pslab-android/actions/runs/16101167033/artifacts/3472568630