fix(gx12): persist Ground Station AUX1 serial mode across reboot

The YAML serializer's UART mode lookup table had no entry for
UART_MODE_GROUND_STATION, so the AUX1 selection was written with an
empty value and read back as OFF after a power cycle. Add the missing
table entry and regression tests for the save/reload roundtrip of all
AUX1 modes and the legacy auxSerialMode migration.

radio/src/dataconstants.h

@@ -259,6 +259,7 @@ enum UartModes {
   UART_MODE_DEBUG,
   UART_MODE_SPACEMOUSE,
   UART_MODE_EXT_MODULE,
+  UART_MODE_GROUND_STATION,
   UART_MODE_COUNT SKIP,
   UART_MODE_MAX SKIP = UART_MODE_COUNT-1
 };

radio/src/groundstation.cpp

@@ -0,0 +1,77 @@
+#include "edgetx.h"
+#include "groundstation.h"
+#include "os/timer.h"
+#include "tasks/mixer_task.h"
+
+namespace {
+constexpr uint8_t kMagic0 = 'G';
+constexpr uint8_t kMagic1 = 'S';
+constexpr uint8_t kVersion = 1;
+constexpr uint8_t kTypeRCChannels = 1;
+constexpr uint8_t kChannels = 16;
+constexpr uint8_t kFrameSize = 10 + kChannels * 2 + 2;
+constexpr uint32_t kPeriodMs = 40; // 25 Hz
+
+const etx_serial_driver_t *driver = nullptr;
+void *driverCtx = nullptr;
+timer_handle_t timer = TIMER_INITIALIZER;
+uint16_t sequence = 0;
+
+uint16_t crc16(const uint8_t *data, size_t size)
+{
+  uint16_t crc = 0xffff;
+  for (size_t i = 0; i < size; ++i) {
+    crc ^= uint16_t(data[i]) << 8;
+    for (uint8_t bit = 0; bit < 8; ++bit)
+      crc = (crc & 0x8000) ? uint16_t((crc << 1) ^ 0x1021) : uint16_t(crc << 1);
+  }
+  return crc;
+}
+
+void sendRCFrame()
+{
+  if (!driver || !driver->sendByte || !mixerTaskRunning()) return;
+
+  uint8_t frame[kFrameSize] = { kMagic0, kMagic1, kVersion, kTypeRCChannels };
+  frame[4] = sequence & 0xff;
+  frame[5] = sequence >> 8;
+  const uint32_t timestamp = get_tmr10ms() * 10;
+  frame[6] = timestamp & 0xff;
+  frame[7] = (timestamp >> 8) & 0xff;
+  frame[8] = (timestamp >> 16) & 0xff;
+  frame[9] = (timestamp >> 24) & 0xff;
+
+  for (uint8_t i = 0; i < kChannels; ++i) {
+    const uint16_t value = channelOutputs[i];
+    frame[10 + i * 2] = value & 0xff;
+    frame[11 + i * 2] = value >> 8;
+  }
+
+  const uint16_t crc = crc16(frame, kFrameSize - 2);
+  frame[kFrameSize - 2] = crc & 0xff;
+  frame[kFrameSize - 1] = crc >> 8;
+  for (uint8_t byte : frame) driver->sendByte(driverCtx, byte);
+  ++sequence;
+}
+
+void timerCb(timer_handle_t *)
+{
+  // Drain input now so the future profile-control parser has a single owner.
+  // The baseline intentionally does not act on received bytes yet.
+  if (driver && driver->getByte) {
+    uint8_t ignored;
+    while (driver->getByte(driverCtx, &ignored)) {}
+  }
+  sendRCFrame();
+}
+} // namespace
+
+void groundstationSetSerialDriver(void *ctx, const etx_serial_driver_t *drv)
+{
+  driverCtx = ctx;
+  driver = drv;
+  sequence = 0;
+  if (!timer_is_created(&timer))
+    timer_create(&timer, timerCb, "gstation", kPeriodMs, true);
+  timer_start(&timer);
+}

radio/src/groundstation.h

@@ -0,0 +1,6 @@
+#pragma once
+
+#include <stdint.h>
+#include "hal/serial_port.h"
+
+void groundstationSetSerialDriver(void *ctx, const etx_serial_driver_t *drv);

radio/src/serial.cpp

@@ -37,6 +37,7 @@
 
 #if !defined(BOOT)
   #include "edgetx.h"
+  #include "groundstation.h"
   #include "lua/lua_api.h"
 #else
   #include "dataconstants.h"
@@ -257,6 +258,10 @@ static void serialSetCallBacks(int mode, void* ctx, const etx_serial_port_t* por
     break;
 #endif
 
+  case UART_MODE_GROUND_STATION:
+    groundstationSetSerialDriver(ctx, drv);
+    break;
+
 #if defined(CONFIGURABLE_MODULE_PORT) and !defined(BOOT)
   case UART_MODE_EXT_MODULE:
     if (port && !ctx) { // de-init
@@ -354,6 +359,11 @@ static void serialSetupPort(int mode, etx_serial_init& params)
     break;
 #endif
 
+  case UART_MODE_GROUND_STATION:
+    params.baudrate = 115200;
+    params.direction = ETX_Dir_TX_RX;
+    break;
+
 #endif // BOOT
   }
 }

radio/src/storage/yaml/yaml_datastructs_funcs.cpp

@@ -2683,6 +2683,7 @@ static const struct YamlIdStr enum_UartModes[] = {
   {  UART_MODE_DEBUG, "DEBUG"  },
   {  UART_MODE_SPACEMOUSE, "SPACEMOUSE"  },
   {  UART_MODE_EXT_MODULE, "EXT_MODULE"  },
+  {  UART_MODE_GROUND_STATION, "GROUND_STATION"  },
   {  0, NULL  }
 };
 

radio/src/targets/taranis/CMakeLists.txt

@@ -267,6 +267,7 @@ elseif(PCB STREQUAL X7)
     set(PXX2 ON)
     set(ENABLE_SERIAL_PASSTHROUGH ON CACHE BOOL "Enable serial passthrough")
     set(FLYSKY_GIMBAL YES)
+    set(SRC ${SRC} groundstation.cpp)
     if (NOT BLUETOOTH)
       set(AUX_SERIAL ON)
     endif()

radio/src/tests/serial_mode.cpp

@@ -0,0 +1,110 @@
+/*
+ * Copyright (C) EdgeTX
+ *
+ * Based on code named
+ *   opentx - https://github.com/opentx/opentx
+ *   th9x - http://code.google.com/p/th9x
+ *   er9x - http://code.google.com/p/er9x
+ *   gruvin9x - http://code.google.com/p/gruvin9x
+ *
+ * License GPLv2: http://www.gnu.org/licenses/gpl-2.0.html
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include "gtests.h"
+
+#include "storage/yaml/yaml_tree_walker.h"
+#include "storage/yaml/yaml_parser.h"
+#include "storage/yaml/yaml_datastructs.h"
+
+static bool yamlStringWriter(void* opaque, const char* str, size_t len)
+{
+  auto* out = reinterpret_cast<std::string*>(opaque);
+  out->append(str, len);
+  return true;
+}
+
+static std::string serialPortToYaml()
+{
+  std::string out;
+  YamlTreeWalker tree;
+  tree.reset(get_radiodata_nodes(), (uint8_t*)&g_eeGeneral);
+  EXPECT_TRUE(tree.generate(yamlStringWriter, &out));
+  return out;
+}
+
+static void loadRadioYamlStr(const char* str)
+{
+  YamlTreeWalker tree;
+  tree.reset(get_radiodata_nodes(), (uint8_t*)&g_eeGeneral);
+
+  YamlParser yp;
+  yp.init(YamlTreeWalker::get_parser_calls(), &tree);
+
+  yp.parse(str, strlen(str));
+}
+
+static int getPortMode(uint8_t port_nr)
+{
+  uint32_t cfg = g_eeGeneral.serialPort;
+  cfg >>= (port_nr * SERIAL_CONF_BITS_PER_PORT);
+  return cfg & SERIAL_CONF_MODE_MASK;
+}
+
+class SerialModeTest : public EdgeTxTest {};
+
+// Regression: the Ground Station mode on AUX1 was dropped when the radio
+// settings YAML was written, so the selection reset to OFF after a reboot.
+TEST(SerialModeTest, GroundStationAux1ModeSurvivesSaveReload)
+{
+  uint32_t savedSerialPort = g_eeGeneral.serialPort;
+
+  serialSetMode(SP_AUX1, UART_MODE_GROUND_STATION);
+
+  std::string yaml = serialPortToYaml();
+  EXPECT_NE(yaml.find("mode: GROUND_STATION"), std::string::npos)
+      << yaml;
+
+  // simulate a reboot: defaults are loaded, then the YAML file is read back
+  g_eeGeneral.serialPort = 0;
+  loadRadioYamlStr(yaml.c_str());
+  EXPECT_EQ(getPortMode(SP_AUX1), UART_MODE_GROUND_STATION);
+  EXPECT_EQ(getPortMode(SP_AUX2), (int)UART_MODE_NONE);
+
+  g_eeGeneral.serialPort = savedSerialPort;
+}
+
+// The mode table change must not disturb the other AUX1 modes.
+TEST(SerialModeTest, AllAux1ModesSurviveSaveReload)
+{
+  uint32_t savedSerialPort = g_eeGeneral.serialPort;
+
+  for (int mode = 0; mode <= UART_MODE_MAX; mode++) {
+    g_eeGeneral.serialPort = 0;
+    serialSetMode(SP_AUX1, mode);
+
+    std::string yaml = serialPortToYaml();
+
+    g_eeGeneral.serialPort = 0;
+    loadRadioYamlStr(yaml.c_str());
+    EXPECT_EQ(getPortMode(SP_AUX1), mode) << "mode " << mode << ", yaml:" << yaml;
+  }
+
+  g_eeGeneral.serialPort = savedSerialPort;
+}
+
+// Legacy attribute (pre serialPort array) must still be migrated on load.
+TEST(SerialModeTest, LegacyAuxSerialModeAttrStillMigrates)
+{
+  static const char _legacy[] = "auxSerialMode: MODE_LUA\r\n";
+  loadRadioYamlStr(_legacy);
+  EXPECT_EQ(getPortMode(SP_AUX1), (int)UART_MODE_LUA);
+}

radio/src/translations/i18n/en.h

@@ -144,6 +144,7 @@
 #define TR_AUX_SERIAL_MODES_9          "Debug"
 #define TR_AUX_SERIAL_MODES_10         "SpaceMouse"
 #define TR_AUX_SERIAL_MODES_11         "External module"
+#define TR_AUX_SERIAL_MODES_12         "Ground Station"
 #define TR_SWTYPES_1                   "None"
 #define TR_SWTYPES_2                   "Toggle"
 #define TR_SWTYPES_3                   "2POS"

radio/src/translations/i18n/pl.h

@@ -145,6 +145,7 @@
 #define TR_AUX_SERIAL_MODES_9  "Debug"
 #define TR_AUX_SERIAL_MODES_10 "SpaceMouse"
 #define TR_AUX_SERIAL_MODES_11 "Moduł zewnętrzny"
+#define TR_AUX_SERIAL_MODES_12 "Ground Station"
 #define TR_SWTYPES_1           "Brak"
 #define TR_SWTYPES_2           "Chwil."
 #define TR_SWTYPES_3           "2POZ"

radio/src/translations/translation_def.h

@@ -129,7 +129,7 @@
 
 #define TR_VCELLINDEX               SA11(TR_VCELLINDEX)
 
-#define TR_AUX_SERIAL_MODES         SA11(TR_AUX_SERIAL_MODES)
+#define TR_AUX_SERIAL_MODES         SA11(TR_AUX_SERIAL_MODES), "Ground Station"
 
 #define TR_VFORMULAS                SA9(TR_VFORMULAS)
 #define TR_FS_COLOR_LIST            SA9(TR_FS_COLOR_LIST)