+
+ def writetxbuffer(self,packet,packbuf=0):
+ """Writes the transmit buffer."""
+
+ self.SPItrans([0x40|(packbuf<<1)]+packet);
+ #READ BACK BUFFER 0 to check what we're about to send out
+ data=self.SPItrans([0x03, 0x31,
+ 0x00,0x00, #SID
+ 0x00,0x00, #EID
+ 0x00, #DLC
+ 0x00, 0x00, 0x00, 0x00,
+ 0x00, 0x00, 0x00, 0x00
+ ]);
+ print "about to transmit:" + self.packet2str(data[2:len(data)]);
+
+ 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.SPItrans([0x81]);
+ self.MCPrts(TXB0=True);
+
+
+ ############### UTILITY FUNCTIONS #################
+
+ 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 packet2parsed(self,data):
+ dp1 = ord(data[0])
+ dp2 = ord(data[1])
+ dp5 = ord(data[4])
+
+ #converts the CAN message to a string
+ msg="";
+ for bar in data:
+ msg=msg+("%02x"%ord(bar))
+
+ packet = {'msg':msg}
+
+ #get the ide bit. allows us to check to see if we have an extended
+ #frame
+ packet['ide'] = (dp2 & 0x0f)>>3
+ #we have an extended frame
+ if( packet['ide'] != 0):
+ #get lower nibble, last 2 bits
+ eId = dp2 & 0x03
+ eId = eId<<8 | ord(data[2])
+ packet['eID'] = eId<<8 | ord(data[3])
+ packet['rtr'] = dp5>>6 & 0x01
+
+ else:
+ packet['rtr'] = dp2>>4 & 0x01
+
+ #error check, 2nd msb of the lower nibble of byte 2 should be 0
+ if( (dp2 & 0x04) == 4 ):
+ packet['error'] = 1
+ #error check an always 0 bit
+ if( (dp5 & 0xf0) == 240):
+ packet['error'] = 1
+
+ # Create the standard ID. from the message
+ packet['sID'] = dp1<<3 | dp2>>5
+
+
+ length = dp5 & 0x0f
+ packet['length'] = length
+
+ if( length > 8):
+ packet['error'] = 1
+
+ #generate the data section
+ for i in range(0,length):
+ idx = 5+i
+ dbidx = 'db%d' % i
+ packet[dbidx] = data[idx]
+ return packet
+
+
+