From 67d824d914e16cdbcea59c0b861967bfbb949051 Mon Sep 17 00:00:00 2001
From: Ted Hess <thess@kitschensync.net>
Date: Sat, 14 Oct 2017 11:39:25 -0400
Subject: [PATCH] Fix parsing of M110 command

---
 Firmware/Marlin_main.cpp | 32 ++++++++++++++++++--------------
 1 file changed, 18 insertions(+), 14 deletions(-)

diff --git a/Firmware/Marlin_main.cpp b/Firmware/Marlin_main.cpp
index d2e098205..66cad9630 100644
--- a/Firmware/Marlin_main.cpp
+++ b/Firmware/Marlin_main.cpp
@@ -1497,14 +1497,16 @@ void get_command()
       }
       cmdbuffer[bufindw+serial_count+1] = 0; //terminate string
       if(!comment_mode){
-		if ((strchr_pointer = strstr(cmdbuffer+bufindw+1, "PRUSA")) == NULL && (strchr_pointer = strchr(cmdbuffer+bufindw+1, 'N')) != NULL) {
-            if ((strchr_pointer = strchr(cmdbuffer+bufindw+1, 'N')) != NULL)
-            {
+	    // Line numbers must be first in buffer
+	    if ((strstr(cmdbuffer+bufindw+1, "PRUSA") == NULL) && 
+		(cmdbuffer[bufindw + 1] == 'N')) {
+
             // Line number met. When sending a G-code over a serial line, each line may be stamped with its index,
             // and Marlin tests, whether the successive lines are stamped with an increasing line number ID.
-            gcode_N = (strtol(strchr_pointer+1, NULL, 10));
-            if(gcode_N != gcode_LastN+1 && (strstr_P(cmdbuffer+bufindw+1, PSTR("M110")) == NULL) ) {
-                // M110 - set current line number.
+            gcode_N = (strtol(cmdbuffer + bufindw + 2, NULL, 10));
+            if ((gcode_N != gcode_LastN + 1) &&
+                (strstr_P(cmdbuffer+bufindw+1, PSTR("M110")) == NULL))
+            {
                 // Line numbers not sent in succession.
                 SERIAL_ERROR_START;
                 SERIAL_ERRORRPGM(MSG_ERR_LINE_NO);
@@ -1542,21 +1544,23 @@ void get_command()
                 return;
             }
 
-            gcode_LastN = gcode_N;
+            // Don't parse N again with code_seen('N')
+            cmdbuffer[bufindw + 1] = '$';
             //if no errors, continue parsing
-            } // end of 'N' command
-        }
-        else  // if we don't receive 'N' but still see '*'
+            gcode_LastN = gcode_N;
+         }
+
+        // if we don't receive 'N' but still see '*'
+        if((cmdbuffer[bufindw + 1] != 'N') && (cmdbuffer[bufindw + 1] != '$') &&
+	   (strchr(cmdbuffer + bufindw + 1, '*') != NULL))
         {
-          if((strchr(cmdbuffer+bufindw+1, '*') != NULL))
-          {
             SERIAL_ERROR_START;
             SERIAL_ERRORRPGM(MSG_ERR_NO_LINENUMBER_WITH_CHECKSUM);
             SERIAL_ERRORLN(gcode_LastN);
             serial_count = 0;
             return;
-          }
-        } // end of '*' command
+        }
+
         if ((strchr_pointer = strchr(cmdbuffer+bufindw+1, 'G')) != NULL) {
       		  if (! IS_SD_PRINTING) {
         			  usb_printing_counter = 10;