Re: [Socketcan-users] socketcan in barebox bootloader

[Marc Kleine-Budde <mkl@pengutronix.de>]

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On 02/10/2012 10:33 AM, Oliver Hartkopp wrote:
>> On 02/09/2012 10:57 PM, Max S. wrote:
>>> CAN is meant for control messages, not for media, or data transfer.
>>
>> In the automotive world it's quite common to do firmware updates over CAN.

> indeed e.g. the ISO 15765-2 protocol is used to segment PDUs up to 4095 byte
> into the 8 byte payload of CAN frames.
> 
> If you want to play with ISO TP on SocketCAN - it's located here:
> 
> https://gitorious.org/linux-can/can-modules/blobs/master/net/can/isotp.c
> 
> But then you would need to implement ISO-TP inside the bootloader too.

That's why I argued to boot into an update linux from the bootloader and
use the existing CAN stack and protocols.

>>> That aside, I do use CAN to flash AVR microchips. It can take a few
>>> minutes though.
>>
>> What throughput do you usually get when updating over CAN?
> 
> 
> I implemented a IP-over-ISOTP tunnel for fun:
> 
> https://gitorious.org/linux-can/can-utils/blobs/master/isotptun.c
> 
> and taking into account that ISO-TP uses the first byte inside the CAN frame
> payload for protocol purposes (1/8 = 12.5% overhead) and the TCP/IP-header of
> 40 byte within the IP communication i got ~26 kByte/s on a 500kbit/s CAN as
> throughput.

There are people that haver narrower DSL lines :)

> Probably that helps to get an impression ;-)

Marc

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