In addition to the firmware version number, store the "PRUSA3D"

magic at the beginning of the EEPROM,
so at the upgrade the firmware would know, if the previous firmware
was a Prusa3D firmware.

Firmware/Configuration.h

@@ -7,7 +7,8 @@
 // Firmware version
 #define FW_version "3.0.5"
 
-
+#define FW_PRUSA3D_MAGIC "PRUSA3DFW"
+#define FW_PRUSA3D_MAGIC_LEN 10
 
 // The total size of the EEPROM is
 // 4096 for the Atmega2560
@@ -30,6 +31,16 @@
 // The offsets are saved as 16bit signed int, scaled to tenths of microns.
 #define EEPROM_BED_CALIBRATION_Z_JITTER   (EEPROM_BED_CALIBRATION_VEC_Y-2*8)
 
+
+// Currently running firmware, each digit stored as uint16_t.
+// The flavor differentiates a dev, alpha, beta, release candidate or a release version.
+#define EEPROM_FIRMWARE_VERSION_FLAVOR    (FW_PRUSA3D_MAGIC_LEN+6)
+#define EEPROM_FIRMWARE_VERSION_REVISION  (FW_PRUSA3D_MAGIC_LEN+4)
+#define EEPROM_FIRMWARE_VERSION_MINOR     (FW_PRUSA3D_MAGIC_LEN+2)
+#define EEPROM_FIRMWARE_VERSION_MAJOR     FW_PRUSA3D_MAGIC_LEN
+// Magic string, indicating that the current or the previous firmware running was the Prusa3D firmware.
+#define EEPROM_FIRMWARE_PRUSA_MAGIC
+
 // This configuration file contains the basic settings.
 // Advanced settings can be found in Configuration_adv.h
 // BASIC SETTINGS: select your board type, temperature sensor type, axis scaling, and endstop configuration

Firmware/util.cpp

@@ -12,6 +12,13 @@ const char* FW_VERSION_STR_P()
     return FW_VERSION_STR;
 }
 
+const char FW_PRUSA3D_MAGIC_STR[] PROGMEM = FW_PRUSA3D_MAGIC;
+
+const char* FW_PRUSA3D_MAGIC_STR_P()
+{
+    return FW_PRUSA3D_MAGIC_STR;
+}
+
 const char STR_REVISION_DEV  [] PROGMEM = "dev";
 const char STR_REVISION_ALPHA[] PROGMEM = "alpha";
 const char STR_REVISION_BETA [] PROGMEM = "beta";
@@ -268,6 +275,8 @@ bool show_upgrade_dialog_if_version_newer(const char *version_string)
 
 void update_current_firmware_version_to_eeprom()
 {
+    for (int8_t i = 0; i < FW_PRUSA3D_MAGIC_LEN; ++ i)
+        eeprom_update_byte((uint8_t*)(EEPROM_FIRMWARE_PRUSA_MAGIC+i), pgm_read_byte(FW_PRUSA3D_MAGIC_STR+i));
     uint16_t ver_current[4];
     if (parse_version_P(FW_VERSION_STR, ver_current)) {
         eeprom_update_word((uint16_t*)EEPROM_FIRMWARE_VERSION_MAJOR,    ver_current[0]);