🚸 UUID fallback to STM32 device SN (#24759)

Co-authored-by: Scott Lahteine <thinkyhead@users.noreply.github.com>

Marlin/src/gcode/host/M115.cpp

   #include "../../feature/caselight.h"
 #endif
 
+#if ENABLED(HAS_STM32_UID) && !defined(MACHINE_UUID)
+  #include "../../libs/hex_print.h"
+#endif
+
 //#define MINIMAL_CAP_LINES // Don't even mention the disabled capabilities
 
 #if ENABLED(EXTENDED_CAPABILITIES_REPORT)
  *       the capability is not present.
  */
 void GcodeSuite::M115() {
-  SERIAL_ECHOLNPGM(
-    "FIRMWARE_NAME:Marlin " DETAILED_BUILD_VERSION " (" __DATE__ " " __TIME__ ") "
-    "SOURCE_CODE_URL:" SOURCE_CODE_URL " "
-    "PROTOCOL_VERSION:" PROTOCOL_VERSION " "
-    "MACHINE_TYPE:" MACHINE_NAME " "
-    "EXTRUDER_COUNT:" STRINGIFY(EXTRUDERS) " "
+  SERIAL_ECHOPGM("FIRMWARE_NAME:Marlin"
+    " " DETAILED_BUILD_VERSION " (" __DATE__ " " __TIME__ ")"
+    " SOURCE_CODE_URL:" SOURCE_CODE_URL
+    " PROTOCOL_VERSION:" PROTOCOL_VERSION
+    " MACHINE_TYPE:" MACHINE_NAME
+    " EXTRUDER_COUNT:" STRINGIFY(EXTRUDERS)
     #if NUM_AXES != XYZ
-      "AXIS_COUNT:" STRINGIFY(NUM_AXES) " "
+      " AXIS_COUNT:" STRINGIFY(NUM_AXES)
     #endif
     #ifdef MACHINE_UUID
-      "UUID:" MACHINE_UUID
+      " UUID:" MACHINE_UUID
     #endif
   );
 
+  // STM32UID:111122223333
+  #if ENABLED(HAS_STM32_UID) && !defined(MACHINE_UUID)
+    // STM32 based devices output the CPU device serial number
+    // Used by LumenPnP / OpenPNP to keep track of unique hardware/configurations
+    // https://github.com/opulo-inc/lumenpnp
+    // Although this code should work on all STM32 based boards
+    SERIAL_ECHOPGM(" UUID:");
+    uint32_t *uid_address = (uint32_t*)UID_BASE;
+    LOOP_L_N(i, 3) {
+      const uint32_t UID = uint32_t(READ_REG(*(uid_address)));
+      uid_address += 4U;
+      for (int B = 24; B >= 0; B -= 8) print_hex_byte(UID >> B);
+    }
+  #endif
+
+  SERIAL_EOL();
+
   #if ENABLED(EXTENDED_CAPABILITIES_REPORT)
 
     // The port that sent M115

Marlin/src/pins/stm32f4/pins_OPULO_LUMEN_REV3.h

 
 // I2C MCP3426 (16-Bit, 240SPS, dual-channel ADC)
 #define HAS_MCP3426_ADC
+#ifdef STM32F4
+  #define HAS_STM32_UID
+#endif
 
 //
 // Servos