2 # GoodFET MCP2515 CAN Bus Client
4 # (C) 2012 Travis Goodspeed <travis at radiantmachines.com>
6 # This code is being rewritten and refactored. You've been warned!
9 # The MCP2515 is a CAN Bus to SPI adapter from Microchip Technology,
10 # as used in the Goodthopter series of boards. It requires a separate
11 # chip for voltage level conversion, such as the MCP2551.
13 import sys, time, string, cStringIO, struct, glob, os;
15 from GoodFETSPI import GoodFETSPI;
17 class GoodFETMCPCAN(GoodFETSPI):
18 """This class uses the regular SPI app to implement a CAN Bus
19 adapter on the Goodthopter10 hardware."""
22 """Sets up the ports."""
24 self.MCPreset(); #Reset the chip.
27 """Reset the MCP2515 chip."""
28 self.SPItrans([0xC0]);
30 def MCPrxstatus(self):
31 """Reads the RX Status by the SPI verb of the same name."""
32 data=self.SPItrans([0xB0,0x00]);
35 def MCPreadstatus(self):
36 """Reads the Read Status by the SPI verb of the same name."""
37 #See page 67 of the datasheet for the flag names.
38 data=self.SPItrans([0xA0,0x00]);
41 def MCPrts(self,TXB0=False,TXB1=False,TXB2=False):
42 """Requests to send one of the transmit buffers."""
44 if TXB0: flags=flags|1;
45 if TXB1: flags=flags|2;
46 if TXB2: flags=flags|4;
49 print "Warning: Requesting to send no buffer.";
51 self.SPItrans([0x80|flags]);
52 def readrxbuffer(self,packbuf=0):
53 """Reads the RX buffer. Might have old data."""
54 data=self.SPItrans([0x90|(packbuf<<2),
58 0x00, 0x00, 0x00, 0x00,
59 0x00, 0x00, 0x00, 0x00
61 return data[1:len(data)];
63 """Reads the next incoming packet from either buffer.
64 Returns None immediately if no packet is waiting."""
65 status=self.MCPrxstatus()&0xC0;
67 #Buffer 0 has higher priority.
68 return self.rxbuffer(0);
70 #Buffer 1 has lower priority.
71 return self.rxbuffer(1);
74 def packet2str(self,packet):
75 """Converts a packet from the internal format to a string."""
78 toprint=toprint+("%02x "%ord(bar))
81 """Read a byte from the given address. Untested."""
82 data=self.SPItrans([0x03,adr&0xFF,00]);
84 def MCPbitmodify(self,adr,mask,data):
85 """Writes a byte with a mask. Doesn't work for many registers."""
86 data=self.SPItrans([0x05,adr&0xFF,mask&0xFF,data&0xFF]);
88 def poke8(self,adr,val):
89 """Poke a value into RAM. Untested"""
90 self.SPItrans([0x02,adr&0xFF,val&0xFF]);