Changeset 742 for trunk/electronics

Timestamp:

06/04/10 22:01:33 (20 months ago)

Author:

kleinjt

Message:

commented MCP setup

Files:

• trunk/electronics/can_killboard/can_killboard.c (modified) (3 diffs)

trunk/electronics/can_killboard/can_killboard.c

@@ -23 +23 @@
         }
 }
+
+// set pin 0 of port C as input for physical kill switch
+// broken out on IO header, see schematic/board layout
 void init_io(void)
 {
@@ -28 +31 @@
 }
 
-// initializes serial
+// initializes serial for 9600 baud
 void init_usart(void)
 {
@@ -122 +125 @@
     mcp_reset();
     mcp_set_mode(ModeConfig);
-        mcp_write_byte(RegCNF1, 0x00);
-    mcp_write_byte(RegCNF2, 0x12);
-    mcp_write_byte(RegCNF3, 0x02);
+        /* QUOTH THE DATSHEET:
+        However, a large SJW is typically
+        only necessary when the clock generation of the different
+        nodes is inaccurate or unstable, such as using
+        ceramic resonators. So a SJW of 1 is usually enough.
+        */
+        mcp_write_byte(RegCNF1, 0x00); //[ SJW1 , SJW0 , BRP5 , BRP4 , BRP3 , BRP2 , BRP1 , BRP0 ], want BRP = 0, TQ = 2 * (BRP + 1) / f_{osc}, TQ = 100ns
+    mcp_write_byte(RegCNF2, 0x12); //[ BTLMODE , SAM , PHSEG12 , PHSEG11 , PHSEG1 , PRSEG2 , PRSEG1 , PRSEG0 ], want PHSEG and PRSEG to be 2 (2 + 1 = 3)
+    mcp_write_byte(RegCNF3, 0x02); //[ SOF , WAKFIL , - , - , - , PHSEG22, PHSEG21 , PHSEG20 ], want PHSEG2 = 2  (PHSEG2 time is = (PHSEG2 + 1) x TQ)
     mcp_set_mode(ModeNormal);
 }