usb and sdcard sharing improvements

* Add traceback after watchdog timeout

Add the cpability to perform a traceback following a watchdog timeout.

* Enhanced hardware SPI

Allow use of either SSP0 or SSP1.
Ensure that no data is left in I/O buffers after calls to enable sharing of SSP hardware.

* Make flash emulation of eeprom the default

Make use of flash for eeprom storage the default. This means that usage of eeprom will not cause USB drive mount/unmount operations.

* Allow sharing of SD card

SD card I/O operations from the USB stack take place in idle loop, rather than at interrupt time. Allowing sharing of the SPI bus.

New configuration options to allow usage of the SD card to be specified.

* Fix problem with hardware SPI pins

Marlin/src/HAL/HAL_LPC1768/main.cpp

@@ -9,7 +9,13 @@
 #include <usb/cdcuser.h>
 #include <usb/mscuser.h>
 #include <CDCSerial.h>
+#include <usb/mscuser.h>
 
+extern "C" {
+  #include <debug_frmwrk.h>
+}
+
+#include "../../sd/cardreader.h"
 #include "../../inc/MarlinConfig.h"
 #include "HAL.h"
 #include "HAL_timers.h"
@@ -41,15 +47,28 @@ void HAL_init() {
       delay(100);
     }
   #endif
-
-  (void)MSC_SD_Init(0);
-
-  USB_Init();
+  //debug_frmwrk_init();
+  //_DBG("\n\nDebug running\n");
+  // Initialise the SD card chip select pins as soon as possible
+  #ifdef SS_PIN
+    digitalWrite(SS_PIN, HIGH);
+    pinMode(SS_PIN, OUTPUT);
+  #endif
+  #ifdef ONBOARD_SD_CS
+    digitalWrite(ONBOARD_SD_CS, HIGH);
+    pinMode(ONBOARD_SD_CS, OUTPUT);
+  #endif
+  USB_Init();                               // USB Initialization
+  USB_Connect(FALSE);                       // USB clear connection
+  delay(1000);                              // Give OS time to notice
   USB_Connect(TRUE);
-
+  #ifndef USB_SD_DISABLED
+    MSC_SD_Init(0);                         // Enable USB SD card access
+  #endif
   const uint32_t usb_timeout = millis() + 2000;
   while (!USB_Configuration && PENDING(millis(), usb_timeout)) {
     delay(50);
+    HAL_idletask();
     #if PIN_EXISTS(LED)
       TOGGLE(LED_PIN);     // Flash quickly during USB initialization
     #endif
@@ -68,4 +87,23 @@ void HAL_init() {
   LPC1768_PWM_init();
 }
 
+// HAL idle task
+void HAL_idletask(void) {
+  #if ENABLED(SDSUPPORT) && defined(SHARED_SD_CARD)
+    // If Marlin is using the SD card we need to lock it to prevent access from
+    // a PC via USB.
+    // Other HALs use IS_SD_PRINTING and IS_SD_FILE_OPEN to check for access but
+    // this will not reliably detect delete operations. To be safe we will lock
+    // the disk if Marlin has it mounted. Unfortuately there is currently no way
+    // to unmount the disk from the LCD menu.
+    // if (IS_SD_PRINTING || IS_SD_FILE_OPEN)
+    if (card.cardOK)
+      MSC_Aquire_Lock();
+    else
+      MSC_Release_Lock();
+  #endif
+  // Perform USB stack housekeeping
+  MSC_RunDeferredCommands();
+}
+
 #endif // TARGET_LPC1768