Re: read() question from newbie

[Wolfgang Grandegger <wg@grandegger.com>]

Hi Michael,

On 04/18/2012 10:13 PM, Michael Economides wrote:
> Hi Oliver,
> 
> Looking on my scope, it does seem like the baudrate is a little off.
> 
> Here are the commands I use to set up my CAN interface on my Linux board:
> 
> insmod -m candev;

Oops, you are using a very very old version of insmod. Are you using
Linux 2.4.x? I do remember using "-m" with old Linux 2.4 distributions.

> insmod -m mscan-mpc52xx;
> insmod -m can;
> insmod -m can-raw
> ifconfig can0 up;
> 
> ./cantest can0 baud 1000000;
> 
> This "cantest" program uses:
> 
>  ifr.ifr_ifru.ifru_ivalue = baudrate;
> ret = ioctl(s, SIOCSCANBAUDRATE, &ifr);
> 
> to set the baudrate.  But it seems from reading other discussions,
> that this is not the correct way to set baud rate.

That's right, in case you are using a recent kernel version.

> I am using the MPC5121 from Freescale, in case that is relevant.

What Linux kernel version do you use? Where did you get the drivers
above from?

Wolfgang.

> On Mon, Apr 16, 2012 at 11:08 PM, Oliver Hartkopp
> <socketcan@hartkopp.net> wrote:
>> On 17.04.2012 06:16, Michael Economides wrote:
>>
>>
>>>>
>>>> I assume there is a CAN bus problem:
>>>>
>>>> - wiring (CAN_L/CAN_H)
>>>> - correct CAN termination (2x 120 Ohms)
>>>> - different bitrate
>>>>
>>>
>>> I think you are right, but I have checked that, it looks ok.  I will
>>> check again.
>>>
>>> I am using a PCAN USB adapter, and the PCAN software says there is an
>>> "acknowledge error" when it sends a frame to my Linux board.
>>
>>
>> This is an indication for a missing counterpart CAN node:
>>
>> - Wrong connection wiring
>> - Wrong termination
>> - Wrong bitrate
>>
>>>
>>> When the Linux board tries to send a frame to PCAN, the PCAN software
>>> says "form error acknowledge delimiter".
>>>
>>> It seems this is the same error in both cases, just worded differently.
>>
>>
>> Yes. But this means the same regarding the obvious problems.
>>
>>>
>>> In your opinion, is this most likely a hardware issue?  Or is there
>>> still some way I could be doing something wrong at the software level?
>>
>>
>> Did you swap CAN_H / CAN_L ??
>>
>> It's definitely one of the three points above. No SW problem ...
>>
>> Try to add a third CAN node - if you have one.
>>
>> Regards,
>> Oliver
> --
> To unsubscribe from this list: send the line "unsubscribe linux-can" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 
>