Jason Gaunt / GMLAN

Libraries to support working with GMLAN - General Motors CAN BUS network in most of their vehicles between 2007-present day. Please note this is a work in progress and not guaranteed to be correct, use at your own risk! Read commit logs / subscribe to see what has been added, it's a work in progress after all ;)

Files at this revision

API Documentation at this revision

Revision 3:09fdfec053cd, committed 2013-02-20

Comitter:
foxdie
Date:
Wed Feb 20 20:10:50 2013 +0000
Parent:
2:1a2cb289f24d
Child:
4:486fec88517e
Commit message:
Added basic support for 11-bit frame headers, changing function names to support

Changed in this revision

GMLAN.cpp Show annotated file Show diff for this revision Revisions of this file
GMLAN.h Show annotated file Show diff for this revision Revisions of this file 
--- a/GMLAN.cpp	Tue Feb 19 22:28:25 2013 +0000
+++ b/GMLAN.cpp	Wed Feb 20 20:10:50 2013 +0000
@@ -19,11 +19,18 @@
 #include "GMLAN.h"
 
 void CANHeader::decode(int _header) {
-    priorityID = (_header >> 26) & 0x7;
-    arbitrationID = (_header >> 13) & 0x1FFF;
-    senderID = (_header >> 0)  & 0x1FFF;
+    if (_header < 0x800)
+    {
+        // 11-bit header
+        arbitrationID = _header;
+    } else {
+        // 29-bit header
+        priorityID = (_header >> 26) & 0x7;
+        arbitrationID = (_header >> 13) & 0x1FFF;
+        senderID = (_header >> 0) & 0x1FFF;
+    }
 }
-int CANHeader::encode(void) {
+int CANHeader::encode29bit(void) {
     long int buffer = 0;
     buffer = (buffer << 3) | 0x0; // 3 bit padding
     buffer = (buffer << 3) | priorityID;

--- a/GMLAN.h	Tue Feb 19 22:28:25 2013 +0000
+++ b/GMLAN.h	Wed Feb 20 20:10:50 2013 +0000
@@ -29,12 +29,24 @@
 #define GMLAN_BAUD_HS 500000
 
 class CANHeader {
-    // Example header packet for Steering Wheel Switches:
-    // Hexadecimal:    0x10     0x0D     0x00     0x60
-    // Binary:       00010000 00001101 00000000 01100000
-    // Priority:        ---
-    // Arbitration:        -- -------- ---
-    // Sending ECU:                       ----- --------
+    /*
+    CANHeader was designed solely for 29-bit frames but supports 11-bit too by just setting the ArbID
+    
+    Example 29-bit header packet from Steering Wheel Switches:
+    
+    Hexadecimal:    0x10     0x0D     0x00     0x60
+    Binary:       00010000 00001101 00000000 01100000
+    Priority:        ---
+    Arbitration:        -- -------- ---
+    Sending ECU:                       ----- --------
+    
+    Example 11-bit header packet from Head Unit:
+    
+    Hexadecimal:    0x02     0x44
+    Binary:       00000010 01000100
+    Identifier:        --- --------
+    
+    */
 
     private:
         int priorityID, arbitrationID, senderID;
@@ -42,22 +54,24 @@
     public:
         // Main function
         CANHeader() { }
-
-        //// 29-bit frames
+        
         // Methods for getting / setting priority, both integers
         int priority(void) { return priorityID; }
         void priority(int _priority) { priorityID = _priority; }
+        
         // Method for getting / setting arbitration id aka arbid, both integers
         int arbitration(void) { return arbitrationID; }
         void arbitration(int _arbitration) { arbitrationID = _arbitration; }
+        
         // Method for getting / setting sender id, both integers
         int sender(void) { return senderID; }
         void sender(int _sender) { senderID = _sender; }
     
-        // Function to decode a header packet and store values in respective variables
+        // Function to decode either an 11-bit or 29-bit header packet and store values in respective variables
         void decode(int _header);
-        // Function to encode stored values and return header packet as int
-        int encode(void);
+        
+        // Function to encode stored values as 29-bit header and return header packet as int
+        int encode29bit(void);
 };
 
 #endif
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