X-Git-Url: http://git.rot13.org/?p=goodfet;a=blobdiff_plain;f=client%2FGoodFETMCPCAN.py;h=0441ecb7b2b78e283213b090606b685f064bd1cc;hp=c00af14307fc509c33ed4599fc140bbd4546818a;hb=5c28c526177571d53654b2a1e47ab5584a399fdf;hpb=d116d8de78feaf5c7a8bb0260c15543298e3d5d2

diff --git a/client/GoodFETMCPCAN.py b/client/GoodFETMCPCAN.py
index c00af14..0441ecb 100644
--- a/client/GoodFETMCPCAN.py
+++ b/client/GoodFETMCPCAN.py
@@ -17,16 +17,86 @@ from GoodFETSPI import GoodFETSPI;
 class GoodFETMCPCAN(GoodFETSPI):
     """This class uses the regular SPI app to implement a CAN Bus
     adapter on the Goodthopter10 hardware."""
-    
+    MCPMODES=["Normal","Sleep","Loopback","Listen-only","Configuration",
+              "UNKNOWN","UNKNOWN","PowerUp"];
     def MCPsetup(self):
         """Sets up the ports."""
         self.SPIsetup();
         self.MCPreset(); #Reset the chip.
         
+        # 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?
+        
+        # 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
+                   );
     def MCPreset(self):
         """Reset the MCP2515 chip."""
         self.SPItrans([0xC0]);
-
+    def MCPcanstat(self):
+        """Get the CAN Status."""
+        return self.peek8(0x0E);
+    def MCPreqstatNormal(self):
+        """Set the CAN state."""
+        state=0x0;
+        self.MCPbitmodify(0x0F,0xE0,(state<<5));
+    def MCPreqstatSleep(self):
+        """Set the CAN state."""
+        state=0x1;
+        self.MCPbitmodify(0x0F,0xE0,(state<<5));
+    def MCPreqstatLoopback(self):
+        """Set the CAN state."""
+        state=0x2;
+        self.MCPbitmodify(0x0F,0xE0,(state<<5));
+    def MCPreqstatListenOnly(self):
+        """Set the CAN state."""
+        state=0x3;
+        self.MCPbitmodify(0x0F,0xE0,(state<<5));
+    def MCPreqstatConfiguration(self):
+        """Set the CAN state."""
+        state=0x4;
+        self.MCPbitmodify(0x0F,0xE0,(state<<5));
+    
+    def MCPcanstatstr(self):
+        """Read the present status as a string."""
+        status=self.MCPcanstat();
+        opmod=(status&0xE0)>>5;
+        return self.MCPMODES[opmod];
     def MCPrxstatus(self):
         """Reads the RX Status by the SPI verb of the same name."""
         data=self.SPItrans([0xB0,0x00]);
@@ -59,6 +129,34 @@ class GoodFETMCPCAN(GoodFETSPI):
                        0x00, 0x00, 0x00, 0x00
                        ]);
         return data[1:len(data)];
+    def writetxbuffer(self,packet,packbuf=0):
+        """Writes the transmit buffer."""
+        self.SPItrans([0x40|(packbuf<<1)]+packet);
+        
+    def rxpacket(self):
+        """Reads the next incoming packet from either buffer.
+        Returns None immediately if no packet is waiting."""
+        status=self.MCPrxstatus()&0xC0;
+        if status&0x40:
+            #Buffer 0 has higher priority.
+            return self.readrxbuffer(0);
+        elif status&0x80:
+            #Buffer 1 has lower priority.
+            return self.readrxbuffer(1);
+        else:
+            return None;
+    def txpacket(self,packet):
+        """Transmits a packet through one of the outbound buffers.
+        As usual, the packet should begin with SIDH.
+        For now, only TXB0 is supported."""
+        self.writetxbuffer(packet,0);
+        self.MCPrts(TXB0=True);
+    def packet2str(self,packet):
+        """Converts a packet from the internal format to a string."""
+        toprint="";
+        for bar in packet:
+            toprint=toprint+("%02x "%ord(bar))
+        return toprint;
     def peek8(self,adr):
         """Read a byte from the given address.  Untested."""
         data=self.SPItrans([0x03,adr&0xFF,00]);