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Vectronix Terrapin-X laser rangefinder protocol
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‎app/src/main/java/com/platypii/baseline/lasers/rangefinder/Crc16.java

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package com.platypii.baseline.lasers.rangefinder;
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class Crc16 {
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/**
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* Computes the CRC16 checksum for a given byte array.
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*/
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public static short crc16(byte[] byteArray) {
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int crc = 0xffff;
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// Process bytes in pairs (LSB first)
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for (int i = 0; i < byteArray.length; i++) {
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int b = byteArray[i] & 0xff;
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crc ^= b;
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// Process each bit
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for (int j = 0; j < 8; j++) {
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if ((crc & 0x0001) != 0) {
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crc = (crc >> 1) ^ 0x8408; // 0x8408 is reversed polynomial
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} else {
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crc = crc >> 1;
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}
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}
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}
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// XOR with 0xfff
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crc ^= 0xffff;
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return (short) crc;
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}
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}

‎app/src/main/java/com/platypii/baseline/lasers/rangefinder/RangefinderService.java

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@@ -30,6 +30,7 @@ public class RangefinderService {
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private final BleProtocol protocols[] = {
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new ATNProtocol(),
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new SigSauerProtocol(),
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new TerrapinProtocol(),
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new UineyeProtocol()
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};
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‎app/src/main/java/com/platypii/baseline/lasers/rangefinder/TerrapinProtocol.java

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package com.platypii.baseline.lasers.rangefinder;
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import com.platypii.baseline.bluetooth.BleException;
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import com.platypii.baseline.bluetooth.BleProtocol;
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import com.platypii.baseline.lasers.LaserMeasurement;
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import com.platypii.baseline.util.Exceptions;
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import android.bluetooth.le.ScanRecord;
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import android.os.ParcelUuid;
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import android.util.Log;
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import androidx.annotation.NonNull;
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import androidx.annotation.Nullable;
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import com.welie.blessed.BluetoothPeripheral;
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import com.welie.blessed.WriteType;
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import java.util.Arrays;
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import java.util.List;
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import java.util.UUID;
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import org.greenrobot.eventbus.EventBus;
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import static com.platypii.baseline.bluetooth.BluetoothUtil.byteArrayToHex;
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import static com.platypii.baseline.bluetooth.BluetoothUtil.toManufacturerString;
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/**
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* This class contains ids, commands, and decoders for Vectronix Terrapin-X laser rangefinders.
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*/
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class TerrapinProtocol extends BleProtocol {
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private static final String TAG = "TerrapinProtocol";
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// Manufacturer ID
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private static final int manufacturerId1 = 1164;
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private static final byte[] manufacturerData1 = {1, -96, -1, -1, -1, -1, 0}; // 01-a0-ff-ff-ff-ff-00
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// Terrapin service
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private static final UUID terrapinService = UUID.fromString("81480000-b0b7-4074-8a24-ae554e5cdbc4");
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// Terrapin characteristic: read, indicate
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private static final UUID terrapinCharacteristic1 = UUID.fromString("81480100-b0b7-4074-8a24-ae554e5cdbc4");
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// Terrapin characteristic: notify, write
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private static final UUID terrapinCharacteristic2 = UUID.fromString("81480200-b0b7-4074-8a24-ae554e5cdbc4");
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private static final String factoryModeSecretKey = "b6987833";
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// Terrapin packet types
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private static final short packetTypeCommand = 0x00;
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private static final short packetTypeData = 0x03;
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private static final short packetTypeAck = 0x04;
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private static final short packetTypeNack = 0x05;
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// Terrapin commands
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private static final short commandNewMeasurementAvailable = 0x1000;
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private static final short commandStartMeasurement = 0x1001;
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private static final short commandGetLastRange = 0x1002;
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private static final short commandGetLastInclination = 0x1003;
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private static final short commandGetLastDirection = 0x1004;
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private static final short commandGetLastTemperature = 0x1005;
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private static final short commandGetLastPressure = 0x1006;
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private static final short commandGetLastEHR = 0x1007;
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private static final short commandGetLaserMode = 0x1022;
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private static final short commandGetDeclination = 0x1027;
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private static final short commandGetRangeGate = 0x1028;
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// private static final short commandGetLastSNR = 0xf006;
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// private static final short commandGetComVersion = 0x01;
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// private static final short commandGetSupportedCommandSet = 0x02;
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// private static final short commandGetSerialNumber = 0x03;
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// private static final short commandActivateFactoryMode = 0x04;
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// private static final short commandGetHardwareRevision = 0x05;
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// private static final short commandGetFirmwareVersion = 0x06;
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// private static final short commandGetBatteryLevel = 0x07;
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// private static final short commandGetDeviceName = 0x08;
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// private static final short commandSetDeviceName = 0x09;
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// private static final short commandGetDeviceId = 0x0a;
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@Override
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public void onServicesDiscovered(@NonNull BluetoothPeripheral peripheral) {
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try {
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// Request rangefinder service
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Log.i(TAG, "app -> rf: subscribe");
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peripheral.setNotify(terrapinService, terrapinCharacteristic1, true);
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} catch (Throwable e) {
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Log.e(TAG, "rangefinder handshake exception", e);
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}
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}
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@Override
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public void processBytes(@NonNull BluetoothPeripheral peripheral, @NonNull byte[] value) {
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Log.d(TAG, "rf -> app: processBytes " + byteArrayToHex(value));
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if (value[0] != 0x7e || value[value.length - 1] != 0x7e) {
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Log.w(TAG, "rf -> app: invalid sentence " + byteArrayToHex(value));
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return;
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}
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// Remove frame
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byte[] frame = Arrays.copyOfRange(value, 1, value.length - 1);
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// Unescape special characters 0x7e and 0x7d
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frame = unescape(frame);
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// Check checksum
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final int checksumValue = getShort(frame, frame.length - 2);
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byte[] checksumContent = Arrays.copyOfRange(frame, 0, frame.length - 2);
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final short checksumComputed = Crc16.crc16(checksumContent);
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if (checksumValue != checksumComputed) {
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Log.w(TAG, "rf -> app: invalid checksum " + byteArrayToHex(checksumContent) + " " + shortToHex(checksumValue) + " != " + shortToHex(checksumComputed));
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}
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// Packet types
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final short packetType = getShort(frame, 0);
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// Data length
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int dataLength = getShort(frame, 2);
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if (dataLength == 512) dataLength = 0;
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// Command
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final int command = getShort(frame, 4);
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if (packetType == packetTypeCommand) {
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final byte[] data = Arrays.copyOfRange(frame, 6, frame.length - 2);
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if (command == commandNewMeasurementAvailable) {
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Log.i(TAG, "rf -> app: new measurement available");
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getLastRange(peripheral);
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} else {
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Log.w(TAG, "rf -> app: command unknown 0x" + shortToHex(command) + " " + dataLength + " " + byteArrayToHex(data));
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}
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} else if (packetType == packetTypeData) {
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Log.i(TAG, "rf -> app: data " + byteArrayToHex(frame));
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} else if (packetType == packetTypeAck) {
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Log.i(TAG, "rf -> app: ack " + byteArrayToHex(frame));
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} else if (packetType == packetTypeNack) {
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Log.i(TAG, "rf -> app: nack " + dataLength + " " + shortToHex(command) + " " + byteArrayToHex(frame));
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} else {
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Log.w(TAG, "rf -> app: unknown packet type " + shortToHex(packetType) + " " + byteArrayToHex(frame));
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}
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}
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private String shortToHex(int value) {
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return Integer.toHexString(value & 0xffff);
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}
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private void processMeasurement(@NonNull byte[] value) {
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Log.d(TAG, "rf -> app: measure " + byteArrayToHex(value));
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// TODO
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EventBus.getDefault().post(new LaserMeasurement(0, 0));
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}
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private void startMeasurement(@NonNull BluetoothPeripheral peripheral) {
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Log.i(TAG, "app -> rf: start measurement");
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sendCommand(peripheral, commandStartMeasurement, null);
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}
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private void getLastRange(@NonNull BluetoothPeripheral peripheral) {
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Log.i(TAG, "app -> rf: get last range");
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sendCommand(peripheral, commandGetLastRange, null);
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}
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private void sendCommand(@NonNull BluetoothPeripheral peripheral, short command, @Nullable byte[] data) {
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final int dataLength = data == null ? 0 : data.length; // TODO: / 2 ?
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byte[] frame = new byte[8 + dataLength];
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// Packet type
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frame[0] = (byte) (packetTypeCommand & 0xff);
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frame[1] = (byte) ((packetTypeCommand >> 8) & 0xff);
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// Data length
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if (data != null) {
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frame[2] = (byte) (dataLength & 0xff);
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frame[3] = (byte) ((dataLength >> 8) & 0xff);
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System.arraycopy(data, 0, frame, 6, data.length);
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} else {
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frame[2] = 2;
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frame[3] = 0;
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}
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// Command
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frame[4] = (byte) (command & 0xff);
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frame[5] = (byte) ((command >> 8) & 0xff);
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// Checksum
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final int checksum = Crc16.crc16(Arrays.copyOfRange(frame, 0, frame.length - 2));
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frame[frame.length - 1] = (byte) ((checksum >> 8) & 0xff);
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frame[frame.length - 2] = (byte) (checksum & 0xff);
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// Escape special characters 0x7e and 0x7d
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frame = escape(frame);
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// Wrap frame
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byte[] wrapped = new byte[frame.length + 2];
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wrapped[0] = 0x7e;
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System.arraycopy(frame, 0, wrapped, 1, frame.length);
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wrapped[wrapped.length - 1] = 0x7e;
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Log.d(TAG, "app -> rf: send command " + byteArrayToHex(wrapped));
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peripheral.writeCharacteristic(terrapinService, terrapinCharacteristic2, wrapped, WriteType.WITH_RESPONSE);
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}
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/**
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* Return true iff a bluetooth scan result looks like a rangefinder
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*/
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@Override
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public boolean canParse(@NonNull BluetoothPeripheral peripheral, @Nullable ScanRecord record) {
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final String deviceName = peripheral.getName();
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if (record != null && Arrays.equals(record.getManufacturerSpecificData(manufacturerId1), manufacturerData1)) {
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return true; // Manufacturer match (kenny's laser)
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} else if (
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(record != null && hasRangefinderService(record))
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|| deviceName.startsWith("FastM")
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|| deviceName.startsWith("Terrapin")) {
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// Send manufacturer data to firebase
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final String mfg = toManufacturerString(record);
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Exceptions.report(new BleException("Terrapin laser unknown mfg data: " + deviceName + " " + mfg));
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return true;
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} else {
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return false;
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}
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}
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private boolean hasRangefinderService(@NonNull ScanRecord record) {
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final List<ParcelUuid> uuids = record.getServiceUuids();
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return uuids != null && uuids.contains(new ParcelUuid(terrapinService));
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}
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private byte[] escape(byte[] data) {
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final byte[] escaped = new byte[data.length * 2];
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int j = 0;
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for (byte b : data) {
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if (b == 0x7e) {
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escaped[j++] = 0x7d;
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escaped[j++] = 0x5e;
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} else if (b == 0x7d) {
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escaped[j++] = 0x7d;
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escaped[j++] = 0x5d;
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} else {
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escaped[j++] = b;
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}
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}
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return Arrays.copyOf(escaped, j);
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}
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private byte[] unescape(byte[] data) {
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final byte[] unescaped = new byte[data.length];
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int j = 0;
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for (int i = 0; i < data.length; i++) {
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if (data[i] == 0x7d) {
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if (data[i + 1] == 0x5e) {
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unescaped[j++] = 0x7e;
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} else if (data[i + 1] == 0x5d) {
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unescaped[j++] = 0x7d;
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} else {
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Log.w(TAG, "rf -> app: invalid escape sequence " + byteArrayToHex(data));
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}
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i++;
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} else {
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unescaped[j++] = data[i];
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}
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}
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return Arrays.copyOf(unescaped, j);
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}
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@NonNull
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private byte[] swapEndianness(@NonNull byte[] data) {
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if (data.length % 2 != 0) {
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Log.w(TAG, "rf -> app: data length must be even " + byteArrayToHex(data));
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}
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final byte[] swapped = new byte[data.length];
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for (int i = 0; i < data.length; i += 2) {
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swapped[i] = data[i + 1];
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swapped[i + 1] = data[i];
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}
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return swapped;
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}
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/**
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* Endian-swapped short from byte array
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*/
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private short getShort(@NonNull byte[] data, int offset) {
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return (short) ((data[offset] & 0xff) | (data[offset + 1] << 8));
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}
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}

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