From ecc09e0b5455ccc4131c6efebf194c2dac4906dc Mon Sep 17 00:00:00 2001
From: Rob Giseburt <giseburt@gmail.com>
Date: Mon, 6 Feb 2017 16:53:11 -0600
Subject: [PATCH] Marlin: *fake* support for SD M-codes (M20, M21, M22, M23)

---
 g2core/gcode_parser.cpp         | 10 ++++++++++
 g2core/marlin_compatibility.cpp | 35 +++++++++++++++++++++++++++++++++
 g2core/marlin_compatibility.h   |  3 +++
 3 files changed, 48 insertions(+)

diff --git a/g2core/gcode_parser.cpp b/g2core/gcode_parser.cpp
index e840d283..469e8264 100644
--- a/g2core/gcode_parser.cpp
+++ b/g2core/gcode_parser.cpp
@@ -751,6 +751,16 @@ stat_t _parse_gcode_block(char *buf, char *active_comment)
                 case 111: return STAT_OK; // ignore M111, and don't process contents of the line further
 
                 case 115: SET_NON_MODAL (next_action, NEXT_ACTION_MARLIN_REPORT_VERSION);
+
+                case 20: // List SD card
+                    return marlin_list_sd_response();
+                case 21: // Initialize SD card
+                case 22: // Release SD card
+                    return STAT_OK;
+
+                case 23: // Select SD file
+                    return marlin_select_sd_response(pstr);
+
 #endif // MARLIN_COMPAT_ENABLED
 
                 default: status = STAT_MCODE_COMMAND_UNSUPPORTED;
diff --git a/g2core/marlin_compatibility.cpp b/g2core/marlin_compatibility.cpp
index e1625f19..6a189972 100644
--- a/g2core/marlin_compatibility.cpp
+++ b/g2core/marlin_compatibility.cpp
@@ -588,4 +588,39 @@ stat_t marlin_report_version()
     return (STAT_OK);
 }
 
+/*
+ * marlin_list_sd_response() - M20
+ *
+ */
+stat_t marlin_list_sd_response()
+{
+    char buffer[128];
+    char *str = buffer;
+
+    str_concat(str, "Begin file list\nEnd file list\n");
+    *str = 0;
+    xio_writeline(buffer);
+
+    return (STAT_OK);
+}
+
+/*
+ * marlin_select_sd_response() - M23
+ *
+ */
+stat_t marlin_select_sd_response(const char *file)
+{
+    char buffer[128];
+    char *str = buffer;
+
+    str_concat(str, "open failed, File: ");
+    strncpy(str, file, Motate::strlen(file));
+    str += Motate::strlen(file);
+    str_concat(str, "\n");
+    *str = 0;
+    xio_writeline(buffer);
+
+    return (STAT_OK);
+}
+
 #endif // MARLIN_COMPAT_ENABLED == true
diff --git a/g2core/marlin_compatibility.h b/g2core/marlin_compatibility.h
index 1f6d50c6..41ef0a3b 100644
--- a/g2core/marlin_compatibility.h
+++ b/g2core/marlin_compatibility.h
@@ -51,4 +51,7 @@ stat_t marlin_disable_motors(); // M84
 stat_t marlin_set_motor_timeout(float s); // M18 Sxxx, M84 Sxxx, M85 Sxxx
 
 stat_t marlin_report_version(); // M115
+
+stat_t marlin_list_sd_response(); // M20
+stat_t marlin_select_sd_response(const char *file); // M23
 #endif  // End of include guard: MARLIN_COMPAT_H_ONCE