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Use resistance measurement to calculate body composition data.

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Coëfficients were obtained by reverse-engineering the discontinued Trisa Vital
Bluetooth app. The resulting figures do not seem to be very accurate.
This commit is contained in:
Maks Verver
2018-10-12 23:09:22 +02:00
parent 9589dc3226
commit b17c1971fb
3 changed files with 113 additions and 14 deletions
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5
android_app/app/src/main/java/com/health/openscale/core/bluetooth/BluetoothTrisaBodyAnalyze.java
View File

@@ -23,7 +23,9 @@ import android.preference.PreferenceManager;
import android.support.annotation.Nullable;
import com.health.openscale.R;
import com.health.openscale.core.OpenScale;
import com.health.openscale.core.datatypes.ScaleMeasurement;
import com.health.openscale.core.datatypes.ScaleUser;
import java.util.UUID;
@@ -252,7 +254,8 @@ public class BluetoothTrisaBodyAnalyze extends BluetoothCommunication {
}
private void onScaleMeasurumentReceived(byte[] data) {
ScaleMeasurement scaleMeasurement = parseScaleMeasurementData(data);
ScaleUser user = OpenScale.getInstance().getSelectedScaleUser();
ScaleMeasurement scaleMeasurement = parseScaleMeasurementData(data, user);
if (scaleMeasurement == null) {
Timber.e("Failed to parse scale measure measurement data: %s", byteInHex(data));
return;

70
android_app/app/src/main/java/com/health/openscale/core/bluetooth/lib/TrisaBodyAnalyzeLib.java
View File

@@ -18,6 +18,8 @@ package com.health.openscale.core.bluetooth.lib;
import android.support.annotation.Nullable;
import com.health.openscale.core.datatypes.ScaleMeasurement;
import com.health.openscale.core.datatypes.ScaleUser;
import com.health.openscale.core.utils.Converters;
import java.util.Date;
@@ -64,25 +66,75 @@ public class TrisaBodyAnalyzeLib {
}
@Nullable
public static ScaleMeasurement parseScaleMeasurementData(byte[] data) {
// Byte 0 contains info.
// Byte 1-4 contains weight.
// Byte 5-8 contains timestamp, if bit 0 in info byte is set.
public static ScaleMeasurement parseScaleMeasurementData(byte[] data, @Nullable ScaleUser user) {
// data contains:
//
// 1 byte: info about presence of other fields:
// bit 0: timestamp
// bit 1: resistance1
// bit 2: resistance2
// (other bits aren't used here)
// 4 bytes: weight
// 4 bytes: timestamp (if info bit 0 is set)
// 4 bytes: resistance1 (if info bit 1 is set)
// 4 bytes: resistance2 (if info bit 2 is set)
// (following fields aren't used here)
// Check that we have at least weight & timestamp, which is the minimum information that
// ScaleMeasurement needs.
if (data.length < 9 || (data[0] & 1) == 0) {
if (data.length < 9) {
return null; // data is too short
}
byte infoByte = data[0];
boolean hasTimestamp = (infoByte & 1) == 1;
boolean hasResistance1 = (infoByte & 2) == 2;
boolean hasResistance2 = (infoByte & 4) == 4;
if (!hasTimestamp) {
return null;
}
double weight = getBase10Float(data, 1);
double weightKg = getBase10Float(data, 1);
int deviceTimestamp = getInt32(data, 5);
ScaleMeasurement measurement = new ScaleMeasurement();
measurement.setDateTime(new Date(convertDeviceTimestampToJava(deviceTimestamp)));
measurement.setWeight((float)weight);
// TODO: calculate body composition (if possible) and set those fields too
measurement.setWeight((float) weightKg);
// Only resistance 2 is used; resistance 1 is 0, even if it is present.
int resistance2Offset = 9 + (hasResistance1 ? 4 : 0);
if (hasResistance2 && resistance2Offset + 4 <= data.length && isValidUser(user)) {
// Calculate body composition statistics from measured weight & resistance, combined
// with age, height and sex from the user profile. The accuracy of the resulting figures
// is questionable, but it's better than nothing. Even if the absolute numbers aren't
// very meaningful, it might still be useful to track changes over time.
double resistance2 = getBase10Float(data, resistance2Offset);
int ageYears = user.getAge();
double heightCm = Converters.toCentimeter(user.getBodyHeight(), user.getMeasureUnit());
boolean isMale = user.getGender().isMale();
double impedance = resistance2 < 410 ? 3.0 : 0.3 * (resistance2 - 400);
double bmi = weightKg * 1e4 / (heightCm * heightCm);
double fat = isMale
? bmi * (1.479 + 4.4e-4 * impedance) + 0.1 * ageYears - 21.764
: bmi * (1.506 + 3.908e-4 * impedance) + 0.1 * ageYears - 12.834;
double water = isMale
? 87.51 + (-1.162 * bmi - 0.00813 * impedance + 0.07594 * ageYears)
: 77.721 + (-1.148 * bmi - 0.00573 * impedance + 0.06448 * ageYears);
double muscle = isMale
? 74.627 + (-0.811 * bmi - 0.00565 * impedance - 0.367 * ageYears)
: 57.0 + (-0.694 * bmi - 0.00344 * impedance - 0.255 * ageYears);
double bone = isMale
? 7.829 + (-0.0855 * bmi - 5.92e-4 * impedance - 0.0389 * ageYears)
: 7.98 + (-0.0973 * bmi - 4.84e-4 * impedance - 0.036 * ageYears);
measurement.setFat((float) fat);
measurement.setWater((float) water);
measurement.setMuscle((float) muscle);
measurement.setBone((float) bone);
}
return measurement;
}
private static boolean isValidUser(@Nullable ScaleUser user) {
return user != null && user.getAge() > 0 && user.getBodyHeight() > 0;
}
private TrisaBodyAnalyzeLib() {}
}

52
android_app/app/src/test/java/com/health/openscale/TrisaBodyAnalyzeLibTest.java
View File

@@ -1,12 +1,16 @@
package com.health.openscale;
import com.health.openscale.core.datatypes.ScaleMeasurement;
import com.health.openscale.core.datatypes.ScaleUser;
import com.health.openscale.core.utils.Converters;
import junit.framework.Assert;
import org.junit.Test;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import static com.health.openscale.core.bluetooth.lib.TrisaBodyAnalyzeLib.convertDeviceTimestampToJava;
import static com.health.openscale.core.bluetooth.lib.TrisaBodyAnalyzeLib.convertJavaTimestampToDevice;
@@ -68,14 +72,49 @@ public class TrisaBodyAnalyzeLibTest {
}
@Test
public void parseScaleMeasurementDataTests() {
public void parseScaleMeasurementData_validUserData() {
long expected_timestamp_seconds = 1539205852L; // Wed Oct 10 21:10:52 UTC 2018
byte[] bytes = hexToBytes("9f:b0:1d:00:fe:dc:2f:81:10:00:00:00:ff:0a:15:00:ff:00:09:00");
ScaleUser user = new ScaleUser();
user.setGender(Converters.Gender.MALE);
user.setBirthday(ageToBirthday(36));
user.setBodyHeight(186);
user.setMeasureUnit(Converters.MeasureUnit.CM);
ScaleMeasurement measurement = parseScaleMeasurementData(bytes, user);
float eps = 1e-3f;
assertEquals(76.0f, measurement.getWeight(), eps);
assertEquals(new Date(expected_timestamp_seconds * 1000), measurement.getDateTime());
assertEquals(14.728368f, measurement.getFat(), eps);
assertEquals(64.37914f, measurement.getWater(), eps);
assertEquals(43.36414f, measurement.getMuscle(), eps);
assertEquals(4.525733f, measurement.getBone());
}
@Test
public void parseScaleMeasurementData_missingUserData() {
long expected_timestamp_seconds = 1538156082L; // Fri Sep 28 17:34:42 UTC 2018
byte[] bytes = hexToBytes("9f:ba:1d:00:fe:32:2b:71:10:00:00:00:ff:8d:14:00:ff:00:09:00");
ScaleMeasurement measurement = parseScaleMeasurementData(bytes);
ScaleMeasurement measurement = parseScaleMeasurementData(bytes, null);
assertEquals(measurement.getWeight(), 76.1f, 1e-6f);
assertEquals(76.1f, measurement.getWeight(), 1e-3f);
assertEquals(new Date(expected_timestamp_seconds * 1000), measurement.getDateTime());
assertEquals(0f, measurement.getFat());
}
@Test
public void parseScaleMeasurementData_invalidUserData() {
long expected_timestamp_seconds = 1538156082L; // Fri Sep 28 17:34:42 UTC 2018
byte[] bytes = hexToBytes("9f:ba:1d:00:fe:32:2b:71:10:00:00:00:ff:8d:14:00:ff:00:09:00");
ScaleMeasurement measurement = parseScaleMeasurementData(bytes, new ScaleUser());
assertEquals(76.1f, measurement.getWeight(), 1e-3f);
assertEquals(new Date(expected_timestamp_seconds * 1000), measurement.getDateTime());
assertEquals(0f, measurement.getFat());
}
/**
@@ -124,7 +163,7 @@ public class TrisaBodyAnalyzeLibTest {
}
/** Parses a colon-separated hex-encoded string like "aa:bb:cc:dd" into an array of bytes. */
private byte[] hexToBytes(String s) {
private static byte[] hexToBytes(String s) {
String[] parts = s.split(":");
byte[] bytes = new byte[parts.length];
for (int i = 0; i < bytes.length; ++i) {
@@ -135,4 +174,9 @@ public class TrisaBodyAnalyzeLibTest {
}
return bytes;
}
private static Date ageToBirthday(int years) {
int currentYear = GregorianCalendar.getInstance().get(Calendar.YEAR);
return new GregorianCalendar(currentYear - years, Calendar.JANUARY, 1).getTime();
}
}