Re: read() question from newbie

[Oliver Hartkopp <socketcan@hartkopp.net>]

On 06.03.2012 19:53, Michael Economides wrote:


> Yes, we removed that line of code with the filtering in cansend.c


fine.

> I ran "candump any", it just sits there, nothing is printed to the
> screen.  So it looks like it thinks nothing is coming across on the
> CAN bus(?)  But like I already stated, on the scope I can see some CAN
> frames being sent to me.


You can check either

cat /proc/net/dev

and

cat /proc/net/can/stats

to see if really any CAN frame entered your system.

I assume there is a CAN bus problem:

- wiring (CAN_L/CAN_H)
- correct CAN termination (2x 120 Ohms)
- different bitrate

> 
> I will be using a Can analyzer tools today, to further my investigation.


Adding some more CAN nodes can help too - so adding another tool and testing
is always a good idea.

> 
> Bascially, all I was asking of you is what could cause read() to wait
> forever... or candump to just sit there and wait?


Well yes. It does a blocking read to get and print receive CAN frames. What do
you expect?

> Maybe the CAN data being sent is not valid (garbage)?


Yes. Please check the three points mentioned above.

Best regards,
Oliver