Add option to prefix USB packet with transmission target

codec2talkie/src/main/java/com/radio/codec2talkie/settings/PreferenceKeys.java

@@ -9,6 +9,8 @@ public final class PreferenceKeys {
     public static String PORTS_USB_PARITY = "ports_usb_parity";
     public static String PORTS_USB_DTR = "ports_usb_dtr";
     public static String PORTS_USB_RTS = "ports_usb_rts";
+    public static String PORTS_USB_IS_PREFIX_ENABLED = "ports_usb_is_prefix_enabled";
+    public static String PORTS_USB_PREFIX = "ports_usb_prefix";
 
     public static String PORTS_BT_CLIENT_NAME = "ports_bt_client_name";
 

codec2talkie/src/main/java/com/radio/codec2talkie/tools/TextTools.java

@@ -53,4 +53,14 @@ public class TextTools {
         }
         return result.toString();
     }
+
+    public static byte[] hexStringToByteArray(String s) {
+        int len = s.length();
+        byte[] data = new byte[len / 2];
+        for (int i = 0; i < len; i += 2) {
+            data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4)
+                    + Character.digit(s.charAt(i+1), 16));
+        }
+        return data;
+    }
 }

codec2talkie/src/main/java/com/radio/codec2talkie/transport/TransportFactory.java

@@ -40,7 +40,7 @@ public class TransportFactory {
 
         switch (transportType) {
             case USB:
-                return new UsbSerial(UsbPortHandler.getPort(), UsbPortHandler.getName());
+                return new UsbSerial(UsbPortHandler.getPort(), UsbPortHandler.getName(), context);
             case BLUETOOTH:
                 return new Bluetooth(BluetoothSocketHandler.getSocket(), BluetoothSocketHandler.getName());
             case TCP_IP:

codec2talkie/src/main/java/com/radio/codec2talkie/transport/UsbSerial.java

@@ -1,9 +1,17 @@
 package com.radio.codec2talkie.transport;
 
+import android.content.Context;
+import android.content.SharedPreferences;
+
+import androidx.preference.PreferenceManager;
+
 import com.hoho.android.usbserial.driver.SerialTimeoutException;
 import com.hoho.android.usbserial.driver.UsbSerialPort;
+import com.radio.codec2talkie.settings.PreferenceKeys;
+import com.radio.codec2talkie.tools.TextTools;
 
 import java.io.IOException;
+import java.nio.ByteBuffer;
 
 public class UsbSerial implements Transport {
 
@@ -13,9 +21,18 @@ public class UsbSerial implements Transport {
     private final UsbSerialPort _usbPort;
     private final String _name;
 
-    public UsbSerial(UsbSerialPort usbPort, String name) {
+    private final boolean _isPrefixEnabled;
+    private final byte[] _bytePrefix;
+
+    protected SharedPreferences _sharedPreferences;
+
+    public UsbSerial(UsbSerialPort usbPort, String name, Context context) {
         _usbPort = usbPort;
         _name = name;
+        _sharedPreferences = PreferenceManager.getDefaultSharedPreferences(context);
+        _isPrefixEnabled = _sharedPreferences.getBoolean(PreferenceKeys.PORTS_USB_IS_PREFIX_ENABLED, false);
+        String prefix = _sharedPreferences.getString(PreferenceKeys.PORTS_USB_PREFIX, "");
+        _bytePrefix = TextTools.hexStringToByteArray(prefix);
     }
 
     @Override
@@ -31,7 +48,15 @@ public class UsbSerial implements Transport {
     @Override
     public int write(byte[] data) throws IOException {
         try {
-            _usbPort.write(data, TX_TIMEOUT);
+            if (_isPrefixEnabled) {
+                byte[] pkt = ByteBuffer.allocate(_bytePrefix.length + data.length)
+                        .put(_bytePrefix)
+                        .put(data)
+                        .array();
+                _usbPort.write(pkt, TX_TIMEOUT);
+            } else {
+                _usbPort.write(data, TX_TIMEOUT);
+            }
             return data.length;
         } catch (SerialTimeoutException e) {
             e.printStackTrace();

codec2talkie/src/main/res/values/strings.xml

@@ -192,6 +192,10 @@
     <string name="usb_stop_bits_title">Serial stop bits</string>
     <string name="usb_serial_title">USB serial settings</string>
     <string name="usb_serial_summary">Set USB serial settings, such as speed, bits, parity, etc.</string>
+    <string name="usb_is_prefix_enabled_title">Enable USB packet prefix</string>
+    <string name="usb_is_prefix_enabled_summary">Prefix USB data with the HEX string for LoRA UART modems</string>
+    <string name="usb_prefix_title">USB packet prefix value as HEX string</string>
+    <string name="usb_prefix_summary">Prefix sent content with a hex string (so called transmission target in UART modems), e.g. C0FFEE</string>
 
     <string name="app_audio_output_speaker_title">Play audio through the speaker</string>
     <string name="app_audio_output_speaker_summary">Output incoming audio through the speaker</string>

codec2talkie/src/main/res/xml/preferences_usb.xml

@@ -54,5 +54,21 @@
             app:summary="@string/usb_rts_summary"
             app:defaultValue="false">
         </CheckBoxPreference>
+
+        <CheckBoxPreference
+            app:key="ports_usb_is_prefix_enabled"
+            app:title="@string/usb_is_prefix_enabled_title"
+            app:summary="@string/usb_is_prefix_enabled_summary"
+            app:defaultValue="false">
+        </CheckBoxPreference>
     </PreferenceCategory>
+
+    <EditTextPreference
+        app:key="ports_usb_prefix"
+        app:title="@string/usb_prefix_title"
+        app:summary = "@string/usb_prefix_summary"
+        app:dependency="ports_usb_is_prefix_enabled"
+        app:defaultValue="C0FFEE">
+    </EditTextPreference>
+
 </PreferenceScreen>