serial can or socket can ?

serial can or socket can ?

[bruce bushby]

Hi

I wanted to confirm my understanding of "socketcan" in terms "slcan0" and "can0"

I've been playing with a Beaglebone board the a usb-can adaptor from
mictronics.de:
http://www.mictronics.de/projects/usb-can-bus/
Purchased from:
http://shop.greenstage.co.nz/product/usb-can-bus-interface

1. Is my understanding correct that "slcan" will ALWAYS be used when
connecting a USB based CANBUS adapter?

I am able to bringup slcan0 using the following commands:
# slcan_attach -o -s6 /dev/ttyUSB0
attached tty /dev/ttyUSB0 to netdevice slcan0
# slcand ttyUSB0
# ifconfig slcan0 up
# ifconfig slcan0
slcan0    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)

#


2. AM335x has an internal D_CAN, but the Beaglebone is missing any CAN
transceiver...would the lack of the transceiver prevent the kernel
from creating the "can0" device?


# lsmod
Module                  Size  Used by    Not tainted
d_can                   5470  0
can_raw                 3679  0
can_dev                 4414  1 d_can
can                    16648  1 can_raw
slcan                   3437  1
ftdi_sio               24056  1
usbserial              18026  3 ftdi_sio

# ip link set can0 up
ip: SIOCGIFFLAGS: No such device

# ifconfig can0
ifconfig: can0: error fetching interface information: Device not found

# ifconfig -a
eth0      Link encap:Ethernet  HWaddr D4:94:A1:89:BC:FF
          inet addr:192.100.1.13  Bcast:0.0.0.0  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:70 errors:0 dropped:0 overruns:0 frame:0
          TX packets:16 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:21678 (21.1 KiB)  TX bytes:1392 (1.3 KiB)
          Interrupt:40

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:3 errors:0 dropped:0 overruns:0 frame:0
          TX packets:3 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:166 (166.0 B)  TX bytes:166 (166.0 B)

slcan0    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)

#


FYI: This is probably a better board if you want to play with CANBUS:
http://www.ti.com/tool/tmdxice3359


Cheers
Bruce

Re: serial can or socket can ?

[Oliver Hartkopp]

On 12.06.2012 14:55, bruce bushby wrote:

> Hi
> 
> I wanted to confirm my understanding of "socketcan" in terms "slcan0" and "can0"
> 


Ok, let's go ...

> I've been playing with a Beaglebone board the a usb-can adaptor from
> mictronics.de:
> http://www.mictronics.de/projects/usb-can-bus/
> Purchased from:
> http://shop.greenstage.co.nz/product/usb-can-bus-interface
> 
> 1. Is my understanding correct that "slcan" will ALWAYS be used when
> connecting a USB based CANBUS adapter?


No.

The slcan driver provides a CAN network device for CAN interfaces that are
controlled by the ASCII protocol first brought up by LAWICEL (www.can232.com,
www.canusb.com). The slcan driver converts the ASCII frames to struct
can_frame which is used in the Linux CAN subsystem (aka SocketCAN).

You may have a CAN device supporting the SLCAN protocol on RS232, USB-serial
adapters, whatever.

See

http://lxr.linux.no/#linux+v3.4.2/drivers/net/can/Kconfig#L13

and

http://lxr.linux.no/#linux+v3.4.2/drivers/net/can/slcan.c#L99

There are CAN USB drivers in the tree, that do not use the SLCAN protocol:

http://lxr.linux.no/#linux+v3.4.2/drivers/net/can/usb/Kconfig


> 
> I am able to bringup slcan0 using the following commands:


Use this

> # slcan_attach -o -s6 /dev/ttyUSB0
> attached tty /dev/ttyUSB0 to netdevice slcan0


OR this

> # slcand ttyUSB0


!

Running slcand and slcan_attach together doesn't make sense.


> # ifconfig slcan0 up
> # ifconfig slcan0
> slcan0    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)
> 
> #
> 
> 
> 2. AM335x has an internal D_CAN, but the Beaglebone is missing any CAN
> transceiver...would the lack of the transceiver prevent the kernel
> from creating the "can0" device?


No. A missing CAN transceiver is not detected (so far).

I assume you need a platform driver specification for your board to find and
access the CAN controller. If you have it, the CAN controller can be accessed
and initialized => can0 appears.

> 
> 
> # lsmod
> Module                  Size  Used by    Not tainted
> d_can                   5470  0
> can_raw                 3679  0
> can_dev                 4414  1 d_can
> can                    16648  1 can_raw
> slcan                   3437  1
> ftdi_sio               24056  1
> usbserial              18026  3 ftdi_sio
> 
> # ip link set can0 up
> ip: SIOCGIFFLAGS: No such device
> 
> # ifconfig can0
> ifconfig: can0: error fetching interface information: Device not found


As expected: Not platform definition => no hardware access => no device

> 
> # ifconfig -a
> eth0      Link encap:Ethernet  HWaddr D4:94:A1:89:BC:FF
>           inet addr:192.100.1.13  Bcast:0.0.0.0  Mask:255.255.255.0
>           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>           RX packets:70 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:16 errors:0 dropped:0 overruns:0 carrier:0
>           collisions:0 txqueuelen:1000
>           RX bytes:21678 (21.1 KiB)  TX bytes:1392 (1.3 KiB)
>           Interrupt:40
> 
> lo        Link encap:Local Loopback
>           inet addr:127.0.0.1  Mask:255.0.0.0
>           UP LOOPBACK RUNNING  MTU:16436  Metric:1
>           RX packets:3 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:3 errors:0 dropped:0 overruns:0 carrier:0
>           collisions:0 txqueuelen:0
>           RX bytes:166 (166.0 B)  TX bytes:166 (166.0 B)
> 
> slcan0    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)
> 
> #
> 
> 
> FYI: This is probably a better board if you want to play with CANBUS:
> http://www.ti.com/tool/tmdxice3359
> 
> 
> Cheers
> Bruce


Regards,
Oliver

Re: serial can or socket can ?

[Marc Kleine-Budde]

[-- Attachment #1: Type: text/plain, Size: 2717 bytes --]

On 06/12/2012 03:44 PM, Oliver Hartkopp wrote:
> On 12.06.2012 14:55, bruce bushby wrote:
> 
>> Hi
>>
>> I wanted to confirm my understanding of "socketcan" in terms "slcan0" and "can0"
>>
> 
> 
> Ok, let's go ...
> 
>> I've been playing with a Beaglebone board the a usb-can adaptor from
>> mictronics.de:
>> http://www.mictronics.de/projects/usb-can-bus/
>> Purchased from:
>> http://shop.greenstage.co.nz/product/usb-can-bus-interface
>>
>> 1. Is my understanding correct that "slcan" will ALWAYS be used when
>> connecting a USB based CANBUS adapter?
> 
> 
> No.
> 
> The slcan driver provides a CAN network device for CAN interfaces that are
> controlled by the ASCII protocol first brought up by LAWICEL (www.can232.com,
> www.canusb.com). The slcan driver converts the ASCII frames to struct
> can_frame which is used in the Linux CAN subsystem (aka SocketCAN).
> 
> You may have a CAN device supporting the SLCAN protocol on RS232, USB-serial
> adapters, whatever.
> 
> See
> 
> http://lxr.linux.no/#linux+v3.4.2/drivers/net/can/Kconfig#L13
> 
> and
> 
> http://lxr.linux.no/#linux+v3.4.2/drivers/net/can/slcan.c#L99
> 
> There are CAN USB drivers in the tree, that do not use the SLCAN protocol:
> 
> http://lxr.linux.no/#linux+v3.4.2/drivers/net/can/usb/Kconfig
> 
> 
>>
>> I am able to bringup slcan0 using the following commands:
> 
> 
> Use this
> 
>> # slcan_attach -o -s6 /dev/ttyUSB0
>> attached tty /dev/ttyUSB0 to netdevice slcan0
> 
> 
> OR this
> 
>> # slcand ttyUSB0
> 
> 
> !
> 
> Running slcand and slcan_attach together doesn't make sense.
> 
> 
>> # ifconfig slcan0 up
>> # ifconfig slcan0
>> slcan0    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)
>>
>> #
>>
>>
>> 2. AM335x has an internal D_CAN, but the Beaglebone is missing any CAN
>> transceiver...would the lack of the transceiver prevent the kernel
>> from creating the "can0" device?

As Oliver said, you need a platform device definition in your board file
and a kernel that supports the d_can hardware. You can use David
Miller's net-next/master tree.

regards, Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
Industrial Linux Solutions        | Phone: +49-231-2826-924     |
Vertretung West/Dortmund          | Fax:   +49-5121-206917-5555 |
Amtsgericht Hildesheim, HRA 2686  | http://www.pengutronix.de   |


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