From abc0edc6356e266e7aff0e5ea1d09c5b0f72aef7 Mon Sep 17 00:00:00 2001
From: Markus Hitter <mah@jump-ing.de>
Date: Sat, 3 Jul 2010 02:24:13 +0200
Subject: [PATCH] Add the option to not include the asterisk in checksum
 calculation. RepRap host software does it this way.

---
 mendel/gcode.c | 11 +++++++++--
 mendel/gcode.h |  4 ++++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/mendel/gcode.c b/mendel/gcode.c
index 645f21c..23faa5c 100644
--- a/mendel/gcode.c
+++ b/mendel/gcode.c
@@ -17,6 +17,8 @@ uint8_t last_field = 0;
 
 const char alphabet[] = "GMXYZEFSPN*";
 
+#define crc(a, b)		(a ^ b)
+
 decfloat read_digit					__attribute__ ((__section__ (".bss")));
 
 GCODE_COMMAND next_target		__attribute__ ((__section__ (".bss")));
@@ -103,10 +105,10 @@ void SpecialMoveE(int32_t e, uint32_t f) {
 ****************************************************************************/
 
 void scan_char(uint8_t c) {
-	// move this below switch(c) if the asterisk isn't included in the checksum
-	#define crc(a, b)		(a ^ b)
+	#ifdef ASTERISK_IN_CHECKSUM_INCLUDED
 	if (next_target.seen_checksum == 0)
 		next_target.checksum_calculated = crc(next_target.checksum_calculated, c);
+	#endif
 
 	// uppercase
 	if (c >= 'a' && c <= 'z')
@@ -290,6 +292,11 @@ void scan_char(uint8_t c) {
 		}
 	}
 
+	#ifndef ASTERISK_IN_CHECKSUM_INCLUDED
+	if (next_target.seen_checksum == 0)
+		next_target.checksum_calculated = crc(next_target.checksum_calculated, c);
+	#endif
+
 	// end of line
 	if ((c == 10) || (c == 13)) {
 		if (debug_flags & DEBUG_ECHO)
diff --git a/mendel/gcode.h b/mendel/gcode.h
index 461036a..075099d 100644
--- a/mendel/gcode.h
+++ b/mendel/gcode.h
@@ -5,6 +5,10 @@
 
 #include	"dda.h"
 
+// wether the asterisk (checksum-command) is included for checksum calculation
+// undefined for RepRap host software
+//#define ASTERISK_IN_CHECKSUM_INCLUDED
+
 // wether to insist on N line numbers
 // if not defined, N's are completely ignored
 //#define	REQUIRE_LINENUMBER