move `enter dfu` to submenu of config

NANOVNA_STM32_F072/board.c

@@ -73,12 +73,16 @@ void __early_init(void) {
   if ( *((unsigned long *)BOOT_FROM_SYTEM_MEMORY_MAGIC_ADDRESS) == BOOT_FROM_SYTEM_MEMORY_MAGIC ) {
     // require irq
     __enable_irq();
+    // reset magic bytes
     *((unsigned long *)BOOT_FROM_SYTEM_MEMORY_MAGIC_ADDRESS) = 0;
     // remap memory. unneeded for F072?
     // RCC->APB2ENR |= RCC_APB2ENR_SYSCFGEN;
     // SYSCFG->CFGR1 = 0x01;
+    // set msp for system memory
     __set_MSP(SYSTEM_BOOT_MSP); 
+    // jump to system memory
     ( (void (*)(void)) (*((uint32_t *)(STM32F072xB_SYSTEM_MEMORY+4))) )();
+    while (1);
   }
 
   //si5351_setup();

ui.c

@@ -421,11 +421,12 @@ enter_dfu(void)
 
   int x = 5, y = 5;
 
+  // leave a last message 
   ili9341_fill(0, 0, 320, 240, 0);
   ili9341_drawstring_5x7("DFU: Device Firmware Update Mode", x, y += 10, 0xffff, 0x0000);
-  ili9341_drawstring_5x7("To exit DFU, please reset device yourself.", x, y += 10, 0xffff, 0x0000);
+  ili9341_drawstring_5x7("To exit DFU mode, please reset device yourself.", x, y += 10, 0xffff, 0x0000);
 
-  // see __early_init in NANOVNA_STM32_F072/board.c
+  // see __early_init in ./NANOVNA_STM32_F072/board.c
   *((unsigned long *)BOOT_FROM_SYTEM_MEMORY_MAGIC_ADDRESS) = BOOT_FROM_SYTEM_MEMORY_MAGIC;
   NVIC_SystemReset();
 }
@@ -541,7 +542,14 @@ menu_config_cb(int item)
       redraw_frame();
       request_to_redraw_grid();
       draw_menu();
-  case 4:
+  }
+}
+
+static void
+menu_dfu_cb(int item)
+{
+  switch (item) {
+  case 0:
       enter_dfu();
   }
 }
@@ -916,12 +924,18 @@ const menuitem_t menu_recall[] = {
   { MT_NONE, NULL, NULL } // sentinel
 };
 
+const menuitem_t menu_dfu[] = {
+  { MT_CALLBACK, "\2RESET AND\0ENTER DFU", menu_dfu_cb },
+  { MT_CANCEL, S_LARROW"CANCEL", NULL },
+  { MT_NONE, NULL, NULL } // sentinel
+};
+
 const menuitem_t menu_config[] = {
   { MT_CALLBACK, "TOUCH CAL", menu_config_cb },
   { MT_CALLBACK, "TOUCH TEST", menu_config_cb },
   { MT_CALLBACK, "SAVE", menu_config_cb },
   { MT_CALLBACK, "VERSION", menu_config_cb },
-  { MT_CALLBACK, "ENTER DFU", menu_config_cb },
+  { MT_SUBMENU, S_RARROW"DFU", menu_dfu },
   { MT_CANCEL, S_LARROW" BACK", NULL },
   { MT_NONE, NULL, NULL } // sentinel
 };