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)

external/CMSIS_5/Device/ARM/ARMv8MML/Include/system_ARMv8MML.h

@@ -0,0 +1,65 @@
+/**************************************************************************//**
+ * @file     system_ARMv8MML.h
+ * @brief    CMSIS Device System Header File for
+ *           ARMv8MML Device
+ * @version  V5.3.3
+ * @date     11. July 2022
+ ******************************************************************************/
+/*
+ * Copyright (c) 2009-2022 Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * 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
+ *
+ * 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.
+ */
+
+#ifndef SYSTEM_ARMv8MML_H
+#define SYSTEM_ARMv8MML_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stdint.h>
+
+/**
+  \brief Exception / Interrupt Handler Function Prototype
+*/
+typedef void(*VECTOR_TABLE_Type)(void);
+
+/**
+  \brief System Clock Frequency (Core Clock)
+*/
+extern uint32_t SystemCoreClock;
+
+
+/**
+  \brief Setup the microcontroller system.
+
+   Initialize the System and update the SystemCoreClock variable.
+ */
+extern void SystemInit (void);
+
+
+/**
+  \brief  Update SystemCoreClock variable.
+
+   Updates the SystemCoreClock with current core Clock retrieved from cpu registers.
+ */
+extern void SystemCoreClockUpdate (void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* SYSTEM_ARMv8MML_H */