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fix: fix data acquisition from SHT21 temperature and humidity sensor #2774

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Merged
merged 1 commit into from
Jul 7, 2025
Merged

fix: fix data acquisition from SHT21 temperature and humidity sensor #2774

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3 changes: 2 additions & 1 deletion app/src/main/java/io/pslab/activity/SensorActivity.java
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ArrayAdapter;
Expand Down Expand Up @@ -192,7 +193,7 @@ protected Void doInBackground(Void... voids) {
// Perform I2C scan to detect connected sensors
detectedSensors = i2c.scan(null);
} catch (IOException | NullPointerException e) {
e.printStackTrace();
Log.w(TAG, "Error scanning for sensors", e);
}
}

Expand Down
10 changes: 3 additions & 7 deletions app/src/main/java/io/pslab/communication/CommunicationHandler.java
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Original file line number Diff line number Diff line change
Expand Up @@ -29,13 +29,10 @@ public class CommunicationHandler {
private UsbSerialDriver driver;
private UsbSerialPort port;
public UsbDevice mUsbDevice;
List<UsbSerialDriver> drivers;

public static final int DEFAULT_READ_BUFFER_SIZE = 32 * 1024;
public static final int DEFAULT_WRITE_BUFFER_SIZE = 32 * 1024;

private byte[] mReadBuffer;
private byte[] mWriteBuffer;

public CommunicationHandler(UsbManager usbManager) {
this.mUsbManager = usbManager;
Expand All @@ -45,7 +42,7 @@ public CommunicationHandler(UsbManager usbManager) {
customTable.addProduct(PSLAB_VENDOR_ID_V6, PSLAB_PRODUCT_ID_V6, Cp21xxSerialDriver.class);

UsbSerialProber prober = new UsbSerialProber(customTable);
drivers = prober.findAllDrivers(usbManager);
List<UsbSerialDriver> drivers = prober.findAllDrivers(usbManager);

if (drivers.isEmpty()) {
Log.d(TAG, "No drivers found");
Expand All @@ -56,7 +53,6 @@ public CommunicationHandler(UsbManager usbManager) {
mUsbDevice = driver.getDevice();
}
mReadBuffer = new byte[DEFAULT_READ_BUFFER_SIZE];
mWriteBuffer = new byte[DEFAULT_WRITE_BUFFER_SIZE];
}

public void open(int baudRate) throws IOException {
Expand Down Expand Up @@ -115,7 +111,7 @@ public int read(byte[] dest, int bytesToBeRead, int timeoutMillis) throws IOExce
bytesToBeReadTemp -= readNow;
}
}
Log.v("Bytes Read", "" + numBytesRead);
Log.v(TAG, "Bytes Read: " + numBytesRead);
return numBytesRead;
}

Expand All @@ -135,7 +131,7 @@ public int readCdcAcm(byte[] dest, int bytesToBeRead, int timeoutMillis) throws
bytesToBeReadTemp -= readNow;
}
}
Log.v("Bytes Read", "" + numBytesRead);
Log.v(TAG, "Bytes Read: " + numBytesRead);
return numBytesRead;
}

Expand Down
17 changes: 13 additions & 4 deletions app/src/main/java/io/pslab/communication/peripherals/I2C.java
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Original file line number Diff line number Diff line change
@@ -1,17 +1,16 @@
package io.pslab.communication.peripherals;

import android.os.SystemClock;
import android.util.Log;

import io.pslab.communication.CommandsProto;
import io.pslab.communication.PacketHandler;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.LinkedHashMap;
import java.util.Map;

import io.pslab.communication.CommandsProto;
import io.pslab.communication.PacketHandler;

/**
* Created by viveksb007 on 28/3/17.
*/
Expand Down Expand Up @@ -140,6 +139,16 @@ public int readStatus() throws IOException {
return val;
}

/**
* Reads data from an I2C device.
*
* @param deviceAddress address of the device to read from
* @param registerAddress address of the register to read from
* @param bytesToRead number of bytes to read from the device
* @return bytes read from the device plus a status byte as the last element (so this will be
* {@code bytesToRead} plus one)
* @throws IOException if data cannot be read
*/
public ArrayList<Integer> readBulk(int deviceAddress, int registerAddress, int bytesToRead) throws IOException {
packetHandler.sendByte(commandsProto.I2C_HEADER);
packetHandler.sendByte(commandsProto.I2C_READ_BULK);
Expand Down
114 changes: 57 additions & 57 deletions app/src/main/java/io/pslab/communication/sensors/SHT21.java
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Original file line number Diff line number Diff line change
Expand Up @@ -2,32 +2,43 @@

import android.util.Log;

import io.pslab.communication.ScienceLab;
import io.pslab.communication.peripherals.I2C;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.concurrent.TimeUnit;

import io.pslab.communication.ScienceLab;
import io.pslab.communication.peripherals.I2C;

/**
* Created by akarshan on 4/16/17.
* Implementation of communication with SHT21 temperature / humidity sensor.
* <p>
* See <a href="https://sensirion.com/media/documents/120BBE4C/63500094/Sensirion_Datasheet_Humidity_Sensor_SHT21.pdf">
* Datasheet SHT21</a> for the calculations for temperature and humidity.
* <p>
* Example code for CRC calculation can be found in the ZIP file
* <a href="https://sensirion.com/resource/software/code/sht21">Sample code SHT21</a>
*/

public class SHT21 {
private String TAG = "SHT21";
private int RESET = 0XFE;
private int TEMP_ADDRESS = 0xF3;
private int HUMIDITY_ADDRESS = 0xF5;
private int selected = 0xF3;
private int ADDRESS = 0x40;

public int NUMPLOTS = 1;
public String[] PLOTNAMES = {"Data"};
public String name = "Humidity/Temperature";
public enum Mode {
TEMPERATURE(TEMP_ADDRESS), HUMIDITY(HUMIDITY_ADDRESS);

public ArrayList<String> selectParameter = new ArrayList<>(Arrays.asList("temperature", "humidity"));
private I2C i2c;
final int registerAddress;

Mode(int registerAddress) {
this.registerAddress = registerAddress;
}
}

private static final String TAG = SHT21.class.getSimpleName();
private static final int RESET = 0XFE;
private static final int TEMP_ADDRESS = 0xE3;
private static final int HUMIDITY_ADDRESS = 0xE5;
private static final int ADDRESS = 0x40;

private Mode selected = Mode.TEMPERATURE;

private final I2C i2c;

public SHT21(I2C i2c, ScienceLab scienceLab) throws IOException, InterruptedException {
this.i2c = i2c;
Expand All @@ -41,38 +52,27 @@ private void init() throws IOException, InterruptedException {
TimeUnit.MILLISECONDS.sleep(100);
}

private ArrayList<Double> rawToTemp(ArrayList<Byte> vals) {
double v;
ArrayList<Double> v1 = new ArrayList<>();
if (vals.size() != 0) {
v = (vals.get(0) << 8) | (vals.get(1) & 0xFC);
v *= 175.72;
v /= (1 << 16);
v -= 46.85;
v1.add(v);
return v1;
private static Double rawToTemp(List<Integer> vals) {
if (vals.size() >= 2) {
double v = ((vals.get(0) & 0xFF) << 8) | (vals.get(1) & 0xFC);
return -46.85 + 175.72 * (v / (1 << 16));
} else return null;
}

private ArrayList<Double> rawToRH(ArrayList<Byte> vals) {
double v;
ArrayList<Double> v1 = new ArrayList<>();
if (vals.size() != 0) {
v = (vals.get(0) << 8) | (vals.get(1) & 0xFC);
v *= 125.;
v /= (1 << 16);
v -= 6;
v1.add(v);
return v1;
private static Double rawToRH(List<Integer> vals) {
if (vals.size() >= 2) {
double v = ((vals.get(0) & 0xFF) << 8) | (vals.get(1) & 0xFC);
return -6 + 125 * (v / (1 << 16));
} else return null;
}

private static int calculateChecksum(ArrayList<Byte> data, int numberOfBytes) {
private static int calculateChecksum(List<Integer> data, int numberOfBytes) {

//CRC
int POLYNOMIAL = 0x131, byteCtr, crc = 0;
final int POLYNOMIAL = 0x31;
int crc = 0;
//calculates 8-Bit checksum with given polynomial
for (byteCtr = 0; byteCtr < numberOfBytes; byteCtr++) {
for (int byteCtr = 0; byteCtr < numberOfBytes; byteCtr++) {
crc ^= data.get(byteCtr);
for (int bit = 8; bit > 0; bit--) {
if ((crc & 0X80) != 0)
Expand All @@ -84,29 +84,29 @@ private static int calculateChecksum(ArrayList<Byte> data, int numberOfBytes) {
return crc;
}

public void selectParameter(String param) {
if (param.equals("temperature"))
selected = TEMP_ADDRESS;
else if (param.equals("humidity"))
selected = HUMIDITY_ADDRESS;
public void setMode(Mode mode) {
selected = mode;
}

public ArrayList<Double> getRaw() throws IOException, InterruptedException {
ArrayList<Byte> vals;
i2c.writeBulk(ADDRESS, new int[]{selected});
if (selected == TEMP_ADDRESS)
public Double getRaw() throws IOException, InterruptedException {
List<Integer> vals;
i2c.writeBulk(ADDRESS, new int[]{selected.registerAddress});
if (selected == Mode.TEMPERATURE)
TimeUnit.MILLISECONDS.sleep(100);
else if (selected == HUMIDITY_ADDRESS)
else if (selected == Mode.HUMIDITY)
TimeUnit.MILLISECONDS.sleep(50);
vals = i2c.simpleRead(ADDRESS, 3);
if (vals.size() != 0) {
if (calculateChecksum(vals, 2) != vals.get(2))
Log.v(TAG, vals.toString());
vals = i2c.readBulk(ADDRESS, selected.registerAddress, 3);
if (vals.isEmpty()) {
Log.v(TAG, "No data received.");
return null;
} else if ((calculateChecksum(vals, 2) & 0xFF) != (vals.get(2) & 0xFF)) {
Log.v(TAG, "Error in checksum.");
return null;
}
if (selected == TEMP_ADDRESS)

if (selected == Mode.TEMPERATURE)
return rawToTemp(vals);
else if (selected == HUMIDITY_ADDRESS)
else if (selected == Mode.HUMIDITY)
return rawToRH(vals);
else
return null;
Expand Down
30 changes: 15 additions & 15 deletions app/src/main/java/io/pslab/fragment/ThermometerDataFragment.java
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Original file line number Diff line number Diff line change
@@ -1,5 +1,8 @@
package io.pslab.fragment;

import static android.content.Context.SENSOR_SERVICE;
import static io.pslab.others.CSVLogger.CSV_DIRECTORY;

import android.graphics.Bitmap;
import android.graphics.Color;
import android.hardware.Sensor;
Expand All @@ -10,17 +13,16 @@
import android.os.Bundle;
import android.os.Environment;
import android.os.Handler;
import androidx.annotation.NonNull;

import com.google.android.material.snackbar.Snackbar;
import androidx.fragment.app.Fragment;

import androidx.preference.PreferenceManager;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.preference.PreferenceManager;

import com.github.anastr.speedviewlib.PointerSpeedometer;
import com.github.mikephil.charting.charts.LineChart;
import com.github.mikephil.charting.components.Legend;
Expand All @@ -29,6 +31,7 @@
import com.github.mikephil.charting.data.Entry;
import com.github.mikephil.charting.data.LineData;
import com.github.mikephil.charting.data.LineDataSet;
import com.google.android.material.snackbar.Snackbar;

import java.io.File;
import java.io.FileNotFoundException;
Expand Down Expand Up @@ -58,12 +61,10 @@
import io.pslab.others.CustomSnackBar;
import io.pslab.others.ScienceLabCommon;

import static android.content.Context.SENSOR_SERVICE;
import static io.pslab.others.CSVLogger.CSV_DIRECTORY;

public class ThermometerDataFragment extends Fragment implements OperationCallback {

private static final String TEMPERATURE = "temperature";
private static final String TAG = ThermometerDataFragment.class.getSimpleName();

private static final CSVDataLine CSV_HEADER = new CSVDataLine()
.add("Timestamp")
.add("DateTime")
Expand Down Expand Up @@ -123,7 +124,7 @@ public static ThermometerDataFragment newInstance() {

public static void setParameters(int updatePeriod, String type, String unit) {
ThermometerDataFragment.updatePeriod = updatePeriod;
ThermometerDataFragment.sensorType = Integer.valueOf(type);
ThermometerDataFragment.sensorType = Integer.parseInt(type);
ThermometerDataFragment.unit = unit;

}
Expand Down Expand Up @@ -356,11 +357,10 @@ public void saveGraph() {
File.separator + CSV_DIRECTORY + File.separator + thermoSensor.getSensorName() +
File.separator + CSVLogger.FILE_NAME_FORMAT.format(new Date()) + "_graph.jpg"));
} catch (FileNotFoundException e) {
e.printStackTrace();
Log.e(TAG, "Unable to save bitmap", e);
}
}


private void setupInstruments() {
setUnit();
XAxis x = mChart.getXAxis();
Expand Down Expand Up @@ -582,15 +582,15 @@ private void initiateThermoSensor(int type) {
data = i2c.scan(null);
if (data.contains(0x39)) {
SHT21 sensorSHT21 = new SHT21(i2c, scienceLab);
sensorSHT21.selectParameter(TEMPERATURE);
sensorSHT21.setMode(SHT21.Mode.TEMPERATURE);
sensorType = 1;
} else {
CustomSnackBar.showSnackBar(getActivity().findViewById(android.R.id.content),
getString(R.string.sensor_not_connected_tls), null, null, Snackbar.LENGTH_SHORT);
sensorType = 0;
}
} catch (IOException | InterruptedException e) {
e.printStackTrace();
Log.e(TAG, "Unable to get data from sensor.", e);
}
} else {
CustomSnackBar.showSnackBar(getActivity().findViewById(android.R.id.content),
Expand Down
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