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/DoxyGen/RTOS/src/RTX/cmsis_os_rtx_extensions.h

@@ -0,0 +1,16 @@
+//  ==== RTX Extensions ====
+
+/// Suspend the RTX task scheduler.
+/// \return number of ticks, for how long the system can sleep or power-down.
+uint32_t os_suspend (void);
+
+/// Resume the RTX task scheduler.
+/// \param[in]     sleep_time    specifies how long the system was in sleep or power-down mode.
+void os_resume (uint32_t sleep_time);
+
+/// OS idle demon (running when no other thread is ready to run).
+__NO_RETURN void os_idle_demon (void);
+
+/// OS error callback (called when a runtime error is detected).
+/// \param[in]     error_code    actual error code that has been detected.
+__NO_RETURN void os_error (uint32_t error_code);