Re: AW: [Socketcan-users] [socketcan]problem to using CAN with BeagleBone Black A5A

[Oliver Hartkopp <socketcan@hartkopp.net>]

On 08.06.2013 23:45, Michael Luxen wrote:

> Did you or anybody else have already some experience on the BeagleBone Black with using the SPI-Interface with MCP2515?

Not yet.

> I'm thinking about to use 1-2 additional CAN-Interfaces to my BeagleBone Black! That means two internal CAN-Interfaces and 2x SPI CAN-Interfaces.
> For example the Cape TT3201 uses two MCP2515 via SPI but I don't know if there are issues with CAN busload above 30% at 500 kbit/s
> http://www.towertech.it/en/products/hardware/tt3201-can-cape/

We were discussing exactly about this board.
AFAIK the CAN Capes have a I2C EEPROM for configuration data which conflicts
with one of the internal DCAN mux pins:

http://circuitco.com/support/index.php?title=TT3201_CAN_Cape#EEPROM

My first idea was to to modify the board in a way that both internal DCAN
interfaces and only one MCP2515 would be connected to the three CAN
transceivers available on the board.

That's why i was happy to see how you made the second DCAN working.

> 
> I'm not sure about the cpu-load, latency and messages lost problems. My experience on the RasperryPi is that 2x MCP2515 on one SPI-Channel doesn't work with busload above 10% at 500kbit/s.

That's not that much. But it's an interesting information to get an estimation
what one might get with this setup.

> IMO the BeagleBone Black has the advantage to use two independent SPI-Channels SPI1 and SPI2 for using a MCP2515 on each SPI channel.

This might be better. But IMO sending all the small messages for the register
accesses is the problem. When serial (e.g. SPI) attached CAN controllers had a
message based programming interface (instead of a register based) using the
SPI would be a real alternative.

Regards,
Oliver


> 
> -----Ursprüngliche Nachricht-----
> Von:	Oliver Hartkopp <socketcan@hartkopp.net>
> Gesendet:	Sa 08.06.2013 13:46
> Betreff:	Re: AW: [Socketcan-users] [socketcan]problem to using CAN with BeagleBone Black A5A
> An:	Michael Luxen <mluxen@gmx.net>; 
> CC:	linux-can@vger.kernel.org; 
>> Hello Mike,
>>
>> thanks for pointing to that comprehensive documentation.
>>
>> I was asked by a colleague how to get both internal CAN controllers working
>> instead of adding SPI-based MCP2515 interfaces.
>>
>> Good job!
>>
>> Best regards,
>> Oliver
>>
>> On 07.06.2013 21:46, Michael Luxen wrote:
>>> Hello Mohamed,
>>>
>>> is you question still open or answered already?
>>>
>>> If still open, please have a look on this page where you can find how to 
>> enable the CAN-Devices on BeagleBone Black.
>>> http://www.aero-box.co.uk/beaglebone-black#TOC-Enable-CANbus-device
>>>
>>> The only thing you have to do is to edit the am335x-bone-common.dtsi file for 
>> enabling dcan0 and/or dcan1.
>>> Please have in mind that dcan0 is normaly used for the optional Capes, as 
>> they use the I2C2 pins which are muxed on the same pins than dcan0.
>>> Nevertheless I've edited am335x-bone-common.dtsi successfully to enable dcan0 
>> and dcan1. On my BeagleBone Black (Hardware A5A) eveything is running fine on 
>> both internal CAN-Interfaces with latest Angstrom and latest Debian as well.
>>> Keep in mind that you have to put a CAN-transceiver on the Pins 20/19 (DCAN0) 
>> an 24/26 (DCAN1) on your BeagleBone Black.
>>>
>>> Regards
>>> Mike
>>>
>>> -----Ursprüngliche Nachricht-----
>>> Von:	Martin Gysel <m.gysel@gmail.com>
>>> Gesendet:	Di 04.06.2013 13:32
>>> Betreff:	Re: [Socketcan-users] [socketcan]problem to using CAN with 
>> BeagleBone Black A5A
>>> An:	linux-can@vger.kernel.org; 
>>> CC:	socketcan-users@lists.berlios.de; 
>>>> Am 25.05.2013 00:49, schrieb Mohamed HAMZAOUI:
>>>>> Hi,
>>>>>
>>>>> I started with beaglebone black A5A, i installed on it the latest
>>>>> Angstrom image with : Linux beaglebone 3.8.13 #1 SMP Mon May 20
>>>>> 17:07:58 CEST 2013 armv7l GNU/Linux
>>>>>
>>>>> I have a problem when I try to add a can device, i load with modprobe
>>>>> all necessary kernel module (can, ti_hecc, c_can, c_can_platform,
>>>>> can-raw, can-bcm) but when i execute
>>>>>> ip link add can0 type can
>>>>> I have : RTNETLINK answers: Operation not supported
>>>>> I used a recent version of iproute2.
>>>>
>>>> did you initialize the can module? do you use a can cape? if yes, does
>>>> your kernel already include the needed dts to enable the can module?
>>>>
>>>> /martin
>>>>
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