Emulate M21 SD card response

prusa3d · Jan 27, 2025 · ebe7455 · ebe7455
1 parent 136fb25
commit ebe7455
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Showing 2 changed files with 7 additions and 1 deletion.
diff --git a/lib/Marlin/Marlin/src/core/language.h b/lib/Marlin/Marlin/src/core/language.h
@@ -225,6 +225,7 @@
 #define MSG_SD_VOL_INIT_FAIL                "volume.init failed"
 #define MSG_SD_OPENROOT_FAIL                "openRoot failed"
 #define MSG_SD_CARD_OK                      "SD card ok"
+#define MSG_SD_CARD_FAIL                    "No SD card"
 #define MSG_SD_WORKDIR_FAIL                 "workDir open failed"
 #define MSG_SD_OPEN_FILE_FAIL               "open failed, File: "
 #define MSG_SD_FILE_OPENED                  "File opened: "

diff --git a/src/marlin_stubs/sdcard/M20-M30_M32-M34.cpp b/src/marlin_stubs/sdcard/M20-M30_M32-M34.cpp
@@ -30,7 +30,12 @@ void GcodeSuite::M20() {
  * M21 - Initialize SD card
  */
 void GcodeSuite::M21() {
-    // not necessary - empty implementation
+    // required for Octoprint / third party tools to simulate an inserted SD card when using USB
+    if (marlin_vars()->media_inserted) {
+        SERIAL_ECHOLNPGM(MSG_SD_CARD_OK);
+    } else {
+        SERIAL_ECHOLNPGM(MSG_SD_CARD_FAIL);
+    }
 }
 
 /**