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)

app/boot_splash.c

@@ -0,0 +1,53 @@
+/* UA1ZBE Custom Firmware - Boot Splash Screen
+ * Displays:
+ *   Line 1 (top, large):  UA1ZBE
+ *   Line 2 (center):       POCSAG pager
+ *   Line 3 (bottom):       YYYY-MM-DD (build date)
+ * Then fades to VFO mode after 2 seconds.
+ */
+
+#include <string.h>
+#include "driver/st7565.h"
+#include "driver/system.h"
+#include "ui/helper.h"
+#include "font.h"
+
+#ifndef BUILD_DATE
+#define BUILD_DATE "unknown"
+#endif
+
+void BOOT_SplashShow(void)
+{
+    /* Clear screen */
+    ST7565_FillScreen(0x00);
+    memset(gStatusLine, 0, sizeof(gStatusLine));
+    for (int line = 0; line < FRAME_LINES; line++)
+        memset(gFrameBuffer[line], 0, LCD_WIDTH);
+
+    /* Line 1: UA1ZBE — large font, centered, top */
+    UI_PrintString("UA1ZBE", 0, LCD_WIDTH, 0, 12);
+
+    /* Line 2: "POCSAG pager" — small font, centered */
+    /* Small font is 6 pixels tall, at y-offset line 3 (~24px) */
+    const char *line2 = "POCSAG pager";
+    int len2 = 0;
+    while (line2[len2]) len2++;
+    int x2 = (LCD_WIDTH - len2 * 6) / 2;
+    if (x2 < 0) x2 = 0;
+    UI_PrintStringSmallNormal(line2, x2, LCD_WIDTH, 24);
+
+    /* Line 3: BUILD_DATE — small font, centered, bottom */
+    const char *date_str = BUILD_DATE;
+    int len3 = 0;
+    while (date_str[len3]) len3++;
+    int x3 = (LCD_WIDTH - len3 * 6) / 2;
+    if (x3 < 0) x3 = 0;
+    UI_PrintStringSmallNormal(date_str, x3, LCD_WIDTH, 48);
+
+    /* Blit to screen */
+    ST7565_BlitStatusLine();
+    ST7565_BlitFullScreen();
+
+    /* Hold for 2 seconds */
+    SYSTEM_DelayMs(2000);
+}