I’ve tried to enable CAN on my BeagleBone Green board. I had to stop the work before verification, because my logic analyzer is unavailable now. I record what I did in this article to make things reproducible when the logic analyzer is back.

There are several helpful links:

http://www.embedded-things.com/bbb/enable-canbus-on-the-beaglebone-black/

http://electronics.stackexchange.com/questions/195416/beaglebone-black-can-bus-setup

https://groups.google.com/forum/embed/?place=forum/beagleboard&showsearch=true&showpopout=true&showtabs=false&hideforumtitle=true&parenturl=http%3A%2F%2Fbeagleboard.org%2Fdiscuss%23bone_forum_embed#!category-topic/beagleboard/can/SjWwVngIPh8

Readings to understand device tree overlay:

Device Tree for Dummies:
http://events.linuxfoundation.jp/sites/events/files/slides/petazzoni-device-tree-dummies.pdf

Device Tree Overlays (in adafruit)
https://learn.adafruit.com/introduction-to-the-beaglebone-black-device-tree/device-tree-overlays

Here are what I did:

# make a workspace
root@beaglebone:~# mkdir can
root@beaglebone:~# cd can
root@beaglebone:~/can# pwd
/root/can

# check if CAN is enabled ... no
root@beaglebone:~/can# dmesg | grep can

# take backup of the original device tree blob file for CAN
root@beaglebone:~/can# cp /lib/firmware/BB-CAN1-00A0.dtbo BB-CAN1-00A0.dtbo.orig

# make the device tree overlay
root@beaglebone:~/can# vi BB-DCAN1-00A0.dts
root@beaglebone:~/can# cat !$
cat BB-DCAN1-00A0.dts
/dts-v1/;
/plugin/;
 
/ {
    compatible = "ti,beaglebone", "ti,beaglebone-black";
 
    /* identification */
    part-number = "dcan1pinmux";
 
    fragment@0 {
        target = <&am33xx_pinmux>;
        __overlay__ {
            dcan1_pins_s0: dcan1_pins_s0 {
                pinctrl-single,pins = <
                    0x180 0x12  /* d_can1_tx, SLEWCTRL_FAST | INPUT_PULLUP | MODE2 */
                    0x184 0x32  /* d_can1_rx, SLEWCTRL_FAST | RECV_ENABLE | INPUT_PULLUP | MODE2 */
                >;
            };
        };
    };
 
    fragment@1 {
        target = <&dcan1>;
        __overlay__ {
             #address-cells = <1>;
             #size-cells = <0>;
 
             status = "okay";
             pinctrl-names = "default";
             pinctrl-0 = <&dcan1_pins_s0>;
        };
    };
};

# install the new device tree blob for CAN
root@beaglebone:~/can# dtc -O dtb -o BB-DCAN1-00A0.dtbo -b 0 -@ BB-DCAN1-00A0.dts
root@beaglebone:~/can# ls
BB-CAN1-00A0.dtbo.orig    BB-DCAN1-00A0.dtbo  BB-DCAN1-00A0.dts
root@beaglebone:~/can# cp BB-DCAN1-00A0.dtbo /lib/firmware/
root@beaglebone:~/can# cmp BB-DCAN1-00A0.dtbo /lib/firmware/BB-DCAN1-00A0.dtbo

# add the device
root@beaglebone:/lib/firmware# cat /sys/devices/platform/bone_capemgr/slots
 0: PF----  -1 
 1: PF----  -1 
 2: PF----  -1 
 3: PF----  -1 
root@beaglebone:~/can# echo BB-DCAN1 > /sys/devices/platform/bone_capemgr/slots 
root@beaglebone:~/can# cat !$
cat /sys/devices/platform/bone_capemgr/slots
 0: PF----  -1 
 1: PF----  -1 
 2: PF----  -1 
 3: PF----  -1 
 4: P-O-L-   0 Override Board Name,00A0,Override Manuf,BB-DCAN1

# check dmesg ... looks fine
root@beaglebone:~/can# dmesg | tail -n15
[   25.499860] wlan0: send auth to 00:1d:73:33:47:a0 (try 1/3)
[   25.522620] wlan0: authenticated
[   25.524815] wl18xx_driver wl18xx.2.auto wlan0: disabling HT/VHT due to WEP/TKIP use
[   25.528911] wlan0: associate with 00:1d:73:33:47:a0 (try 1/3)
[   25.538576] wlan0: RX AssocResp from 00:1d:73:33:47:a0 (capab=0x431 status=0 aid=4)
[   25.764831] wlan0: associated
[   25.765114] IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
[   26.579282] wlcore: Association completed.
[ 3395.588267] bone_capemgr bone_capemgr: part_number 'BB-DCAN1', version 'N/A'
[ 3395.588337] bone_capemgr bone_capemgr: slot #4: override
[ 3395.588380] bone_capemgr bone_capemgr: Using override eeprom data at slot 4
[ 3395.588425] bone_capemgr bone_capemgr: slot #4: 'Override Board Name,00A0,Override Manuf,BB-DCAN1'
[ 3395.613523] bone_capemgr bone_capemgr: slot #4: dtbo 'BB-DCAN1-00A0.dtbo' loaded; overlay id #0
[ 3395.648848] CAN device driver interface
[ 3395.689001] c_can_platform 481d0000.can: c_can_platform device registered (regs=fa1d0000, irq=192)

# load CAN modules
root@beaglebone:~/can# sudo modprobe can
root@beaglebone:~/can# sudo modprobe can-dev
root@beaglebone:~/can# sudo modprobe can-raw
root@beaglebone:~/can# lsmod | grep can
can_raw                 5852  0 
can                    28397  1 can_raw
c_can_platform          6602  0 
c_can                   9577  1 c_can_platform
can_dev                11663  1 c_can

# Startup the CAN interface. Set CAN channel rate 500kbps.
root@beaglebone:~# ip link set can0 up type can bitrate 500000
root@beaglebone:~# ifconfig can0
can0      Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  
          UP RUNNING NOARP  MTU:16  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:10 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
          Interrupt:192 

# Check the device status. Status UNKNOWN doesn't sound right...
root@beaglebone:~/can# ip -d -s link show can0
4: can0: <NOARP,UP,LOWER_UP,ECHO> mtu 16 qdisc pfifo_fast state UNKNOWN mode DEFAULT group default qlen 10
    link/can  promiscuity 0 
    can state ERROR-ACTIVE (berr-counter tx 0 rx 0) restart-ms 0 
      bitrate 125000 sample-point 0.875 
      tq 500 prop-seg 6 phase-seg1 7 phase-seg2 2 sjw 1
      c_can: tseg1 2..16 tseg2 1..8 sjw 1..4 brp 1..1024 brp-inc 1
      clock 24000000
      re-started bus-errors arbit-lost error-warn error-pass bus-off
      0          0          0          0          0          0         
    RX: bytes  packets  errors  dropped overrun mcast   
    0          0        0       0       0       0      
    TX: bytes  packets  errors  dropped carrier collsns 
    0          0        0       0       0       0      

Then I have to stop here.