add CDC mode only for use with Arduino touch 1200

fix issue with reading current.uf2 size when flashed with jlink

src/usb/uf2/ghostfat.c

@@ -135,7 +135,14 @@ static uint32_t get_flash_size(void)
       const bootloader_settings_t * boot_setting;
       bootloader_util_settings_get(&boot_setting);
 
+      // if bank0 size is not valid, happens when flashed with jlink
+      // use maximum application size
+
       flash_sz = boot_setting->bank_0_size;
+      if ( (flash_sz == 0) || (flash_sz == 0xFFFFFFFFUL) )
+      {
+        flash_sz = FLASH_SIZE;
+      }
     }
   }
 

src/usb/usb.c

@@ -44,11 +44,16 @@
 
 #include "nrf_usbd.h"
 #include "tusb.h"
+#include "usb_desc.h"
 
 //--------------------------------------------------------------------+
 // MACRO TYPEDEF CONSTANT ENUM DECLARATION
 //--------------------------------------------------------------------+
 
+// from usb_desc.c for dynamic descriptor
+extern tusb_desc_device_t usb_desc_dev;
+extern usb_desc_cfg_t     usb_desc_cfg;
+
 /* tinyusb function that handles power event (detected, ready, removed)
  * We must call it within SD's SOC event handler, or set it as power event handler if SD is not enabled. */
 extern void tusb_hal_nrf_power_event(uint32_t event);
@@ -95,6 +100,16 @@ void usb_init(bool cdc_only)
     tusb_hal_nrf_power_event(NRFX_POWER_USB_EVT_READY);
   }
 
+  if ( cdc_only )
+  {
+    // Change PID to CDC only
+    usb_desc_dev.idProduct = USB_DESC_SERIAL_ONLY_PID;
+
+    // Remove MSC interface = reduce total interface + adjust config desc length
+    usb_desc_cfg.config.bNumInterfaces--;
+    usb_desc_cfg.config.wTotalLength -= sizeof(usb_desc_cfg.msc);
+  }
+
   // Init tusb stack
   tusb_init();
 }

src/usb/usb_desc.h

@@ -85,9 +85,6 @@ typedef struct ATTR_PACKED
 } usb_desc_cfg_t;
 
 
-extern tusb_desc_device_t usb_desc_dev;
-extern usb_desc_cfg_t     usb_desc_cfg;
-
 #ifdef __cplusplus
  }
 #endif