Re: [Socketcan-users] socketcan in barebox bootloader

[Oliver Hartkopp <socketcan@hartkopp.net>]

On 10.02.2012 09:55, Marc Kleine-Budde wrote:

> Now with linux-can on Cc :)
> 
> 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.


Hi,

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 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.

Probably that helps to get an impression ;-)

Regards,
Oliver