thispostwalksthroughsettingupacancontrollerontheraspberrypi.mygoalistohelpdemystifytheprocess， andprovidesimpleinstructionsthatarelativebeginnershouldbeabletofollow.particularly，includinginformationthatiwishwasmoresmorerereareare
bytheendofthistutorialyoushouldhaveaworkingcanconnectedtotheraspberrypiviathespibus.usingsocketcanitwilbepossible tosendandandresible linuxipstack.thismeansyoucanalysecanpacketsjustasyouwouldwithtcp/IP，usingstandardutilitiesliketcpdumpandwireshark.add usingutilitieslikecandump/cansendprovidedbycan-utils，youcanremoveanextralayerofabstraction，andfocuspurelyonthecandatalecandatals
Getting the Hardware
youhaveafairamountofchoiceswhenitcomestohardware.themostdiscussedandmostpopularmodulesusethemcp 2515 can-SPI chip，soI'llFCP
Some options are:
-picanbySKyydz32.28Incvat(~$46 ) -链接
- can-bussheldbysparkfun---- $ 25-link
- ebay-less than $2(search for ' MCP 2515 module ' ) )。
ichosetogowiththecheapebaymodule (pictured above )、 notthattheotheralternativesweren ' t great.thesparkfunshieldlookedveryinterestingwithamicrosdslotfordatalogging，and hook up fup butsinceiwaslearninganddidn ' twanttoendupbrickinganicepieceofhardwarejustyet，I went the cheaper route。
youshouldbeabletofollowthisguidefortheothermodulesaswell，you ' lljusthavetodeterminethewiringbylookingattheschematicsforyour
ifoundsomeschematicsfortheebaymodule-pdf
Note，theebaymoduleusesthetja 1050 can transceiver，whiletheothersusethemcp 2551.notsureifitmakesmuchofadifference，butthoughoughetthorence
Wiring it Up
thisshouldapplytoallthemodulesimentioned，thoughthelabelingmaybeabitdifferent.pinout.xyzhasasupercoolinteractiveractiverpipinout
RPi Pin RPi Label CAN Module
02------ 5v-----VCC
06------ gnd-----gnd
19--------gpio10----mosi () ) ) )。
21------ gpio9---
-----MISO (SO)22---------GPIO25--------INT
23---------GPIO11--------SCK
24---------GPIO8---------CS
Enabling the SPI Bus and Loading the Kernel Modules
Edit /boot/config.txt and add the following lines, setting the oscillator parameter to that of the oscillator present on the module. Most of the modules use a 16MHz oscillator for the clock, though the Ebay module uses 8MHz oscillator=8000000. You can determine the frequency by looking at the chip.
Reboot.
If everything is hooked up and working the can0 interface should be visible with ifconfig can.
pi@raspberrypi:~ $ ifconfig can
can0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
NOARP MTU:16 Metric:1
collisions:0 txqueuelen:10
The MCP2515 device tree overlay parameters are described in /boot/overlays/README.
Name: mcp2515-can0
Info: Configures the MCP2515 CAN controller on spi0.0
Load: dtoverlay=mcp2515-can0,=
Params: oscillator Clock frequency for the CAN controller (Hz)
spimaxfrequency Maximum SPI frequence (Hz)
interrupt GPIO for interrupt signal
Compiling Can-utils
You may need to install some prerequisites:
sudo apt-get install git autoconf libtool
Run the following commands to compile can-utils:
git clone https://github.com/linux-can/can-utils.git
cd can-utils
./autogen.sh
./configure
make
sudo make install
You may also install via the repository:
sudo apt-get install can-utils
Bring Up the Interface
You can bring up the interface with:
sudo ip link set can0 up type can bitrate 50000
You'll need to select the proper bitrate for the network you're connecting to. Common bitrates are: 10000, 20000, 50000, 100000, 125000, 250000, 500000, 800000, 1000000.
If you need to change a setting, first bring down the interface:
sudo ip link set can0 down
You can see a list of available settings by appending help to the command:
pi@raspberrypi:~ $ ip link set can0 up type can bitrate 50000 help
Usage: ip link set DEVICE type can
phase-seg2 PHASE-SEG2 [ sjw SJW ] ]
dphase-seg2 PHASE-SEG2 [ dsjw SJW ] ]
Where: BITRATE := { 1..1000000 }
SAMPLE-POINT := { 0.000..0.999 }
TQ := { NUMBER }
PROP-SEG := { 1..8 }
PHASE-SEG1 := { 1..8 }
PHASE-SEG2 := { 1..8 }
SJW := { 1..4 }
RESTART-MS := { 0 | NUMBER }
The loopback setting enables loopback mode on the MCP2515, which can be useful for verifying that the RPi is communicating with the CAN module without having to connect to an actual CAN bus. All messages transmitted in loopback mode will be echoed back over the interface.
Listen-only can be useful if you're interested in sniffing CAN traffic, and want to lessen the risk of messing something up by ensuring the device doesn't send any packets.
Send and Receive CAN Messages
Using cansend/candump it's possible to respectively send and receive CAN messages.
Send
cansend can0 001#1122334455667788
And receive:
candump can0
On some cars you may not see any traffic through the CAN-bus on the OBD2 port. This is due to the fact that there is a 'gateway' present between the OBD2 port and the various CAN networks. The gateway acts like a firewall between the networks, and it's necessary to send a request for data before it can be received.