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/RTOS2/RTX/Config/RTX_Config.c

@@ -0,0 +1,67 @@
+/*
+ * Copyright (c) 2013-2023 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.
+ *
+ * -----------------------------------------------------------------------------
+ *
+ * $Revision:   V5.2.0
+ *
+ * Project:     CMSIS-RTOS RTX
+ * Title:       RTX Configuration
+ *
+ * -----------------------------------------------------------------------------
+ */
+ 
+#include "cmsis_compiler.h"
+#include "rtx_os.h"
+ 
+// OS Idle Thread
+__WEAK __NO_RETURN void osRtxIdleThread (void *argument) {
+  (void)argument;
+
+  for (;;) {}
+}
+ 
+// OS Error Callback function
+__WEAK uint32_t osRtxErrorNotify (uint32_t code, void *object_id) {
+  (void)object_id;
+
+  switch (code) {
+    case osRtxErrorStackOverflow:
+      // Stack overflow detected for thread (thread_id=object_id)
+      break;
+    case osRtxErrorISRQueueOverflow:
+      // ISR Queue overflow detected when inserting object (object_id)
+      break;
+    case osRtxErrorTimerQueueOverflow:
+      // User Timer Callback Queue overflow detected for timer (timer_id=object_id)
+      break;
+    case osRtxErrorClibSpace:
+      // Standard C/C++ library libspace not available: increase OS_THREAD_LIBSPACE_NUM
+      break;
+    case osRtxErrorClibMutex:
+      // Standard C/C++ library mutex initialization failed
+      break;
+    case osRtxErrorSVC:
+      // Invalid SVC function called (function=object_id)
+      break;
+    default:
+      // Reserved
+      break;
+  }
+  for (;;) {}
+//return 0U;
+}