Merge pull request #4092 from thinkyhead/rc_sd_error

Output a message for SD read errors

Marlin/Marlin_main.cpp

@@ -1140,6 +1140,10 @@ inline void get_serial_commands() {
           card.printingHasFinished();
           card.checkautostart(true);
         }
+        else if (n == -1) {
+          SERIAL_ERROR_START;
+          SERIAL_ECHOLNPGM(MSG_SD_ERR_READ);
+        }
         if (sd_char == '#') stop_buffering = true;
 
         sd_comment_mode = false; //for new command

Marlin/language.h

@@ -171,6 +171,7 @@
 #define MSG_SD_PRINTING_BYTE                "SD printing byte "
 #define MSG_SD_NOT_PRINTING                 "Not SD printing"
 #define MSG_SD_ERR_WRITE_TO_FILE            "error writing to file"
+#define MSG_SD_ERR_READ                     "SD read error"
 #define MSG_SD_CANT_ENTER_SUBDIR            "Cannot enter subdir: "
 
 #define MSG_STEPPER_TOO_HIGH                "Steprate too high: "