X-Git-Url: http://git.rot13.org/?p=goodfet;a=blobdiff_plain;f=client%2FGoodFETMCPCAN.py;h=7182d3706d7e9cf80a5a8d0f296aa78649aeb871;hp=d4dc1590cc4f5fad9de1cd08d9aa8146a1e97b91;hb=4ac8acb7df57251bc53db2102da617269801e793;hpb=9565c64a06b7302cd820214f58ea0970d4f1e07a

diff --git a/client/GoodFETMCPCAN.py b/client/GoodFETMCPCAN.py
index d4dc159..7182d37 100644
--- a/client/GoodFETMCPCAN.py
+++ b/client/GoodFETMCPCAN.py
@@ -24,8 +24,104 @@ class GoodFETMCPCAN(GoodFETSPI):
         self.SPIsetup();
         self.MCPreset(); #Reset the chip.
         
-        #Loopback mode for testing.
+        # We're going to set some registers, so we must be in config
+        # mode.
         self.MCPreqstatConfiguration();
+        
+        # If we don't enable promiscous mode, we'll miss a lot of
+        # packets.  It can be manually disabled later.
+        #self.poke8(0x60,0xFF); #TODO Does this have any unpleasant side effects?
+        self.poke8(0x60,0x66); #Wanted FF, but some bits are reserved.
+        
+        #Set the default rate.
+        self.MCPsetrate();
+    
+    #Array of supported rates.
+    MCPrates=[83.3, 100, 125,
+              250, 500, 1000];
+    
+    def MCPsetrate(self,rate=125):
+        """Sets the data rate in kHz."""
+        # Now we need to set the timing registers.  See chapter 5 of
+        # the MCP2515 datasheet to get some clue as to how this
+        # arithmetic of this works, as my comments here will likely be
+        # rambling, incoherent, and unchanged after I get the infernal
+        # thing working.
+        
+        # First, we must chose a Time Quanta (QT) which is used to
+        # define the durations of these segments.  Section 5.3
+        # suggests setting BRP<5:0> to 0x04 to get a TQ=500ns, as a 20
+        # MHz crystal gives a clock period of 50ns.  This way, for 125
+        # kHz communication, the bit time must be 16 TQ.
+        
+        # A bit consists of four parts:
+        # 1: SyncSeg             1 TQ
+        # 2: PropSeg             2 TQ
+        # 3: PhaseSeg1 (PS1)     7 TQ
+        # 4: PhaseSeg2 (PS2)     6 TQ
+        
+        # CNF1 with a prescaler of 4 and a SJW of 1 TQ.  SJW of 4
+        # might be more stable.
+        #self.poke8(0x2a,0x04);
+        
+        # CNF2 with a BLTMODE of 1, SAM of 0, PS1 of 7TQ, and PRSEG of 2TQ
+        #self.poke8(0x29,
+        #           0x80   |  # BTLMODE=1
+        #           (6<<3) |  # 6+1=7TQ for PHSEG1
+        #           (1)       # 1+1=2TQ for PRSEG
+        #           );
+        
+        #CNF3 with a PS2 length of 6TQ.
+        #self.poke8(0x28,
+        #           5      #5+1=6TQ
+        #           );
+        
+        
+        print "Setting rate of %i kHz." % rate;
+        
+        #These are the new examples.
+        if rate==125:
+            #125 kHz, 16 TQ, not quite as worked out above.
+            CNF1=0x04;
+            CNF2=0xB8;
+            CNF3=0x05;
+        elif rate==100:
+            #100 kHz, 20 TQ
+            CNF1=0x04;
+            CNF2=0xBA;
+            CNF3=0x07;
+        elif rate>83 and rate<83.5:
+            #83+1/3 kHz, 8 TQ
+            # 0.04% error from 83.30
+            CNF1=0x0E;
+            CNF2=0x90;
+            CNF3=0x02;
+        elif rate==250:
+            #256 kHz, 20 TQ
+            CNF1=0x01;
+            CNF2=0xBA;
+            CNF3=0x07;
+        elif rate==500:
+            #500 kHz, 20 TQ
+            CNF1=0x00;
+            CNF2=0xBA;
+            CNF3=0x07;
+        elif rate==1000:
+            #1,000 kHz, 10 TQ
+            CNF1=0x00;
+            CNF2=0xA0;
+            CNF3=0x02;
+            print "WARNING: Because of chip errata, this probably won't work."
+        else:
+            print "Given unsupported rate of %i kHz." % rate;
+            print "Defaulting to 125kHz.";
+            CNF1=0x04;
+            CNF2=0xB8;
+            CNF3=0x05;
+        self.poke8(0x2a,CNF1);
+        self.poke8(0x29,CNF2);
+        self.poke8(0x28,CNF3);
+        
     def MCPreset(self):
         """Reset the MCP2515 chip."""
         self.SPItrans([0xC0]);
@@ -129,4 +225,8 @@ class GoodFETMCPCAN(GoodFETSPI):
     def poke8(self,adr,val):
         """Poke a value into RAM.  Untested"""
         self.SPItrans([0x02,adr&0xFF,val&0xFF]);
+        newval=self.peek8(adr);
+        if newval!=val:
+            print "Failed to poke %02x to %02x.  Got %02x." % (adr,val,newval);
+            print "Are you not in idle mode?";
         return val;