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)

helper/boot.c

@@ -0,0 +1,111 @@
+/* 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 <string.h>
+
+#ifdef ENABLE_AIRCOPY
+	#include "app/aircopy.h"
+#endif
+#include "bsp/dp32g030/gpio.h"
+#include "driver/bk4819.h"
+#include "driver/keyboard.h"
+#include "driver/gpio.h"
+#include "driver/system.h"
+#include "helper/boot.h"
+#include "misc.h"
+#include "radio.h"
+#include "settings.h"
+#include "ui/menu.h"
+#include "ui/ui.h"
+
+BOOT_Mode_t BOOT_GetMode(void)
+{
+	unsigned int i;
+	KEY_Code_t   Keys[2];
+
+	for (i = 0; i < 2; i++)
+	{
+		if (GPIO_CheckBit(&GPIOC->DATA, GPIOC_PIN_PTT))
+			return BOOT_MODE_NORMAL;   // PTT not pressed
+		Keys[i] = KEYBOARD_Poll();
+		SYSTEM_DelayMs(20);
+	}
+
+	if (Keys[0] == Keys[1])
+	{
+		gKeyReading0 = Keys[0];
+		gKeyReading1 = Keys[0];
+
+		gDebounceCounter = 2;
+
+		if (Keys[0] == KEY_SIDE1)
+			return BOOT_MODE_F_LOCK;
+
+		#ifdef ENABLE_AIRCOPY
+			if (Keys[0] == KEY_SIDE2)
+				return BOOT_MODE_AIRCOPY;
+		#endif
+	}
+
+	return BOOT_MODE_NORMAL;
+}
+
+void BOOT_ProcessMode(BOOT_Mode_t Mode)
+{
+	if (Mode == BOOT_MODE_F_LOCK)
+	{
+		GUI_SelectNextDisplay(DISPLAY_MENU);
+	}
+	#ifdef ENABLE_AIRCOPY
+		else
+		if (Mode == BOOT_MODE_AIRCOPY)
+		{
+			gEeprom.DUAL_WATCH               = DUAL_WATCH_OFF;
+			gEeprom.BATTERY_SAVE             = 0;
+			#ifdef ENABLE_VOX
+				gEeprom.VOX_SWITCH           = false;
+			#endif
+			gEeprom.CROSS_BAND_RX_TX         = CROSS_BAND_OFF;
+			gEeprom.AUTO_KEYPAD_LOCK         = false;
+			gEeprom.KEY_1_SHORT_PRESS_ACTION = ACTION_OPT_NONE;
+			gEeprom.KEY_1_LONG_PRESS_ACTION  = ACTION_OPT_NONE;
+			gEeprom.KEY_2_SHORT_PRESS_ACTION = ACTION_OPT_NONE;
+			gEeprom.KEY_2_LONG_PRESS_ACTION  = ACTION_OPT_NONE;
+			gEeprom.KEY_M_LONG_PRESS_ACTION  = ACTION_OPT_NONE;
+
+			RADIO_InitInfo(gRxVfo, FREQ_CHANNEL_LAST - 1, 41002500);
+
+			gRxVfo->CHANNEL_BANDWIDTH        = BANDWIDTH_WIDE;
+			gRxVfo->OUTPUT_POWER             = OUTPUT_POWER_LOW;
+
+			RADIO_ConfigureSquelchAndOutputPower(gRxVfo);
+
+			gCurrentVfo = gRxVfo;
+
+			RADIO_SetupRegisters(true);
+			BK4819_SetupAircopy();
+			BK4819_ResetFSK();
+
+			gAircopyState = AIRCOPY_READY;
+
+			GUI_SelectNextDisplay(DISPLAY_AIRCOPY);
+		}
+	#endif
+	else
+	{
+		GUI_SelectNextDisplay(DISPLAY_MAIN);
+	}
+}