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/Mutex.c

@@ -0,0 +1,52 @@
+#include "cmsis_os2.h"                          // CMSIS RTOS header file
+ 
+/*----------------------------------------------------------------------------
+ *      Mutex creation & usage
+ *---------------------------------------------------------------------------*/
+ 
+osMutexId_t mid_Mutex;                          // mutex id
+ 
+osThreadId_t tid_Thread_Mutex;                  // thread id
+ 
+void Thread_Mutex (void *argument);             // thread function
+ 
+int Init_Mutex (void) {
+ 
+  mid_Mutex = osMutexNew(NULL);
+  if (mid_Mutex == NULL) {
+    ; // Mutex object not created, handle failure
+  }
+ 
+  tid_Thread_Mutex = osThreadNew(Thread_Mutex, NULL, NULL);
+  if (tid_Thread_Mutex == NULL) {
+    return(-1);
+  }
+ 
+  return(0);
+}
+ 
+void Thread_Mutex (void *argument) {
+  osStatus_t status;
+ 
+  while (1) {
+    ; // Insert thread code here...
+ 
+    status = osMutexAcquire(mid_Mutex, 0U);
+    switch (status) {
+      case osOK:
+        ; // Use protected code here...
+        osMutexRelease(mid_Mutex);
+        break;
+      case osErrorResource:
+        break;
+      case osErrorParameter:
+        break;
+      case osErrorISR:
+        break;
+      default:
+        break;
+    }
+ 
+    osThreadYield();                            // suspend thread
+  }
+}