PRUSA SN in eeprom

Firmware/Marlin_main.cpp

@@ -407,6 +407,7 @@ static void gcode_M105(uint8_t extruder);
 static void temp_compensation_start();
 static void temp_compensation_apply();
 
+static bool get_PRUSA_SN(char* SN);
 
 uint16_t gcode_in_progress = 0;
 uint16_t mcode_in_progress = 0;
@@ -1075,6 +1076,21 @@ void setup()
           if(!(eeprom_read_byte((uint8_t*)EEPROM_FAN_CHECK_ENABLED)))
                eeprom_update_byte((unsigned char *)EEPROM_FAN_CHECK_ENABLED,true);
 	}
+
+
+    if (eeprom_read_byte((uint8_t*)EEPROM_PRUSA_SN + 19)) //saved EEPROM SN is not valid. Try to retrieve it.
+    {
+        char SN[20];
+        if (get_PRUSA_SN(SN))
+        {
+            eeprom_update_block(SN, (uint8_t*)EEPROM_PRUSA_SN, 20);
+            puts_P(PSTR("SN updated"));
+        }
+        else
+            puts_P(PSTR("SN update failed"));
+    }
+
+
 #ifndef W25X20CL
 	SERIAL_PROTOCOLLNPGM("start");
 #else
@@ -3386,25 +3402,26 @@ void gcode_M701()
  *
  * Typical format of S/N is:CZPX0917X003XC13518
  *
- * Command operates only in farm mode, if not in farm mode, "Not in farm mode." is written to MYSERIAL.
- *
  * Send command ;S to serial port 0 to retrieve serial number stored in 32U2 processor,
- * reply is transmitted to serial port 1 character by character.
+ * reply is transmitted to the selected serial port.
  * Operation takes typically 23 ms. If the retransmit is not finished until 100 ms,
  * it is interrupted, so less, or no characters are retransmitted, only newline character is send
  * in any case.
+ * The command will fail if the 32U2 processor is unpowered via USB since it is isolated from the rest of the electronics.
+ * In that case the value that is stored in the EEPROM should be used instead.
+ *
+ * @return 1 on success
  */
-static void gcode_PRUSA_SN()
+static bool get_PRUSA_SN(char* SN)
 {
     uint8_t selectedSerialPort_bak = selectedSerialPort;
-    char SN[20];
     selectedSerialPort = 0;
     SERIAL_ECHOLNRPGM(PSTR(";S"));
     uint8_t numbersRead = 0;
     ShortTimer timeout;
     timeout.start();
 
-    while (numbersRead < (sizeof(SN) - 1)) {
+    while (numbersRead < 19) {
         if (MSerial.available() > 0) {
             SN[numbersRead] = MSerial.read();
             numbersRead++;
@@ -3413,7 +3430,7 @@ static void gcode_PRUSA_SN()
     }
     SN[numbersRead] = 0;
     selectedSerialPort = selectedSerialPort_bak;
-    SERIAL_ECHOLN(SN);
+    return (numbersRead == 19);
 }
 //! Detection of faulty RAMBo 1.1b boards equipped with bigger capacitors
 //! at the TACH_1 pin, which causes bad detection of print fan speed.
@@ -3950,7 +3967,12 @@ void process_commands()
         card.openFile(strchr_pointer+4,false);
 
 	} else if (code_seen("SN")) { // PRUSA SN
-        gcode_PRUSA_SN();
+        char SN[20];
+        eeprom_read_block(SN, (uint8_t*)EEPROM_PRUSA_SN, 20);
+        if (SN[19])
+            puts_P(PSTR("SN invalid"));
+        else
+            puts(SN);
 
 	} else if(code_seen("Fir")){ // PRUSA Fir
 

Firmware/eeprom.h

@@ -316,6 +316,7 @@ static_assert(sizeof(Sheets) == EEPROM_SHEETS_SIZEOF, "Sizeof(Sheets) is not EEP
 | 0x0D29 3369		| uint8		| EEPROM_PINDA_TEMP_COMPENSATION   		| ffh 255		| ffh 255				| PINDA temp compensation unknown state	            | LCD menu		| D3 Ax0d29 C1
 | ^					| ^			| ^										| 00h 0			| ^						| PINDA has no temp compensation PINDA v1/2    		| ^				| ^
 | ^					| ^			| ^										| 01h 1			| ^						| PINDA has temp compensation aka SuperPINDA       	| ^				| ^
+| 0x0D15 3349		| char[20]	| EEPROM_PRUSA_SN						| SN[19] == 0	| ffffffffffffffff...	| PRUSA Serial number string						| PRUSA SN		| D3 Ax0d15 C20
 
   
 | Address begin		| Bit/Type 	| Name 									| Valid values	| Default/FactoryReset	| Description 										| Gcode/Function| Debug code
@@ -521,8 +522,9 @@ static Sheets * const EEPROM_Sheets_base = (Sheets*)(EEPROM_SHEETS_BASE);
 #define EEPROM_ALTFAN_OVERRIDE (EEPROM_UVLO_LA_K-1) //uint8
 #define EEPROM_EXPERIMENTAL_VISIBILITY (EEPROM_ALTFAN_OVERRIDE-1) //uint8
 #define EEPROM_PINDA_TEMP_COMPENSATION (EEPROM_EXPERIMENTAL_VISIBILITY-1) //uint8
+#define EEPROM_PRUSA_SN (EEPROM_PINDA_TEMP_COMPENSATION-20) //char[20]
 //This is supposed to point to last item to allow EEPROM overrun check. Please update when adding new items.
-#define EEPROM_LAST_ITEM EEPROM_PINDA_TEMP_COMPENSATION
+#define EEPROM_LAST_ITEM EEPROM_PRUSA_SN
 // !!!!!
 // !!!!! this is end of EEPROM section ... all updates MUST BE inserted before this mark !!!!!
 // !!!!!