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/Template/Events.c

@@ -0,0 +1,51 @@
+#include "cmsis_os2.h"                          // CMSIS RTOS header file
+ 
+/*----------------------------------------------------------------------------
+ *  Event Flags creation & usage
+ *---------------------------------------------------------------------------*/
+ 
+#define FLAGS_MSK1 0x00000001U
+ 
+osEventFlagsId_t evt_id;                        // event flasg id
+ 
+osThreadId_t tid_Thread_EventSender;            // thread id 1
+osThreadId_t tid_Thread_EventReceiver;          // thread id 2
+ 
+void Thread_EventSender   (void *argument);     // thread function 1
+void Thread_EventReceiver (void *argument);     // thread function 2
+ 
+int Init_Events (void) {
+ 
+  evt_id = osEventFlagsNew(NULL);
+  if (evt_id == NULL) {
+    ; // Event Flags object not created, handle failure
+  }
+ 
+  tid_Thread_EventSender = osThreadNew(Thread_EventSender, NULL, NULL);
+  if (tid_Thread_EventSender == NULL) {
+    return(-1);
+  }
+  tid_Thread_EventReceiver = osThreadNew(Thread_EventReceiver, NULL, NULL);
+  if (tid_Thread_EventReceiver == NULL) {
+    return(-1);
+  }
+
+  return(0);
+}
+ 
+void Thread_EventSender (void *argument) {
+ 
+  while (1) {    
+    osEventFlagsSet(evt_id, FLAGS_MSK1);
+    osThreadYield();                            // suspend thread
+  }
+}
+ 
+void Thread_EventReceiver (void *argument) {
+  uint32_t flags;
+ 
+  while (1) {
+    flags = osEventFlagsWait(evt_id, FLAGS_MSK1, osFlagsWaitAny, osWaitForever);
+    //handle event
+  }
+}