UA1ZBE Custom Firmware v1.0

Features:
- VFO mode with direct frequency input
- POCSAG decoder (512/1200 baud) with BCH(31,21) correction
- Full-screen Spectrum analyzer
- FM Radio receiver
- RSSI signal indicator overlay
- Custom boot splash (UA1ZBE / POCSAG pager / build date)

Architecture:
- app/mode.c — mode dispatcher (VFO/POCSAG/Spectrum/FM)
- app/boot_splash.c — 2-second boot splash
- app/pocsag/ — POCSAG decoder + BCH correction
- app/display_rssi.c — RSSI indicator
- main.c — entry point with custom init
- syscalls.c — bare-metal _sbrk stub

Build: arm-none-eabi-gcc -Os -flto -Wall -Werror -Wextra
Size: 57.9KB Flash / 3.6KB RAM

Controls:
- 0-9: Direct frequency input (VFO)
- SK2: POCSAG mode
- SK1: Spectrum analyzer
- 0: FM Radio
- EXIT: Return to VFO
- F/*: Toggle 512/1200 baud (in POCSAG)

ui/ui.c

@@ -0,0 +1,97 @@
+/* Copyright 2023 Dual Tachyon
+ * https://github.com/DualTachyon
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *     Unless required by applicable law or agreed to in writing, software
+ *     distributed under the License is distributed on an "AS IS" BASIS,
+ *     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *     See the License for the specific language governing permissions and
+ *     limitations under the License.
+ */
+
+#include <assert.h>
+#include <string.h>
+
+#include "app/chFrScanner.h"
+#include "app/dtmf.h"
+#ifdef ENABLE_FMRADIO
+	#include "app/fm.h"
+#endif
+#include "driver/keyboard.h"
+#include "misc.h"
+#ifdef ENABLE_AIRCOPY
+	#include "ui/aircopy.h"
+#endif
+#ifdef ENABLE_FMRADIO
+	#include "ui/fmradio.h"
+#endif
+#include "ui/inputbox.h"
+#include "ui/main.h"
+#include "ui/menu.h"
+#include "ui/scanner.h"
+#include "ui/ui.h"
+#include "../misc.h"
+
+GUI_DisplayType_t gScreenToDisplay;
+GUI_DisplayType_t gRequestDisplayScreen = DISPLAY_INVALID;
+
+uint8_t           gAskForConfirmation;
+bool              gAskToSave;
+bool              gAskToDelete;
+
+
+void (*UI_DisplayFunctions[])(void) = {
+	[DISPLAY_MAIN] = &UI_DisplayMain,
+	[DISPLAY_MENU] = &UI_DisplayMenu,
+	[DISPLAY_SCANNER] = &UI_DisplayScanner,
+
+#ifdef ENABLE_FMRADIO
+	[DISPLAY_FM] = &UI_DisplayFM,
+#endif
+
+#ifdef ENABLE_AIRCOPY
+	[DISPLAY_AIRCOPY] = &UI_DisplayAircopy,
+#endif
+};
+
+static_assert(ARRAY_SIZE(UI_DisplayFunctions) == DISPLAY_N_ELEM);
+
+void GUI_DisplayScreen(void)
+{
+	if (gScreenToDisplay != DISPLAY_INVALID) {
+		UI_DisplayFunctions[gScreenToDisplay]();
+	}
+}
+
+void GUI_SelectNextDisplay(GUI_DisplayType_t Display)
+{
+	if (Display == DISPLAY_INVALID)
+		return;
+
+	if (gScreenToDisplay != Display)
+	{
+		DTMF_clear_input_box();
+
+		gInputBoxIndex       = 0;
+		gIsInSubMenu         = false;
+		gCssBackgroundScan         = false;
+		gScanStateDir        = SCAN_OFF;
+		#ifdef ENABLE_FMRADIO
+			gFM_ScanState    = FM_SCAN_OFF;
+		#endif
+		gAskForConfirmation  = 0;
+		gAskToSave           = false;
+		gAskToDelete         = false;
+		gWasFKeyPressed      = false;
+
+		gUpdateStatus        = true;
+	}
+
+	gScreenToDisplay = Display;
+	gUpdateDisplay   = true;
+}