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/CMSIS/RTOS/RTX/SRC/rt_System.h

@@ -0,0 +1,42 @@
+/*----------------------------------------------------------------------------
+ *      CMSIS-RTOS  -  RTX
+ *----------------------------------------------------------------------------
+ *      Name:    RT_SYSTEM.H
+ *      Purpose: System Task Manager definitions
+ *      Rev.:    V4.79
+ *----------------------------------------------------------------------------
+ *
+ * Copyright (c) 1999-2009 KEIL, 2009-2017 ARM Germany GmbH. 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.
+ *---------------------------------------------------------------------------*/
+
+/* Variables */
+#define os_psq  ((P_PSQ)&os_fifo)
+extern S32 os_tick_irqn;
+
+/* Functions */
+extern U32  rt_suspend    (void);
+extern void rt_resume     (U32 sleep_time);
+extern void rt_tsk_lock   (void);
+extern void rt_tsk_unlock (void);
+extern void rt_psh_req    (void);
+extern void rt_pop_req    (void);
+extern void rt_systick    (void);
+extern void rt_stk_check  (void);
+
+/*----------------------------------------------------------------------------
+ * end of file
+ *---------------------------------------------------------------------------*/