erasing MBR table before creating a new partitioning scheme

Author: andreagilardoni

Diff for: libraries/STM32H747_System/examples/QSPIFormat/QSPIFormat.ino

@@ -60,6 +60,33 @@ void setup() {
   Serial.println("Do you want to proceed? Y/[n]");
 
   if (true == waitResponse()) {
+    if (root.init() != QSPIF_BD_ERROR_OK) {
+      Serial.println(F("Error: QSPI init failure."));
+      return;
+    }
+
+    const size_t pts = 512; // MBR partition table size = 512b
+    const size_t erase_size = root.get_erase_size(0x0);
+
+    size_t remainder = pts % erase_size;
+    size_t division = pts / erase_size;
+
+    uint8_t *buf = nullptr;
+
+    // save the data that exceeded the size of MBR partition table and write it back
+    if(remainder != 0) {
+      buf = (uint8_t*) malloc(erase_size - remainder);
+      root.read(buf, division*erase_size, sizeof(buf));
+    }
+
+    root.erase(0x0, erase_size*(division + remainder == 0? 0 : 1)); // clear the MBR partition table
+
+    if(remainder != 0) {
+      root.program(buf, division*erase_size, sizeof(buf));
+      free(buf);
+      buf = nullptr;
+    }
+
     mbed::MBRBlockDevice::partition(&root, 1, 0x0B, 0, 1024 * 1024);
     if(default_scheme) {
       mbed::MBRBlockDevice::partition(&root, 3, 0x0B, 14 * 1024 * 1024, 14 * 1024 * 1024);