On 02/10/2012 10:33 AM, Oliver Hartkopp wrote:

quoted

On 02/09/2012 10:57 PM, Max S. wrote:

quoted

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.

quoted

quoted

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

-- 
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   |