CAN on 18F2580

Joules · Joined: 02 Mar 2006 Posts: 9

Hi, I'm new to the board.

I'm developing a system using a 18F2580 and am having no luck getting it to recieve CAN messages. I can send them just fine, and when I only have 2 nodes on the bus I don't get any error frames (kvaser leaf is one node, the 2580 is the other), so I don't think it's hardware or the BRGCON registers.

The recieve functions in the EX_CAN program don't even work (only changes I made where specifying the correct device.h and the clock). again, xmit works fine.

any thoughts on this?

sjbaxter · Joined: 26 Jan 2006 Posts: 141 Location: Cheshire, UK

Have you terminated the bus correctly ? Error frames are usually created from either bus termination being incorrect or a node on the bus is the wrong bit rate.

What kind of interval are you messages being sent at and what is the bus load ?

Give us some more info and a snippet of the program you are using to rx/tx can messages.

What is the other node that you are putting on the bus as that may be causing the error frames ?

What clock freq are you using, what bit rate are you after and what have you set the BRGCON registers to ?
_________________
Regards,
Simon.

Joules · Joined: 02 Mar 2006 Posts: 9

That's just it, I'm not getting any error frames, it's just not receiving data. I've got the 120-ohm resistor on the 2580. When I send data from the 2580 I can receive it on the other node. The CAN transceiver I'm using on this node is a TI SN65HVD251. The reason I thought it wasn't hardware or bus timing is because no errors are being generated.

The other node is a kvaser leaf (connected to a pc), I've tried sending messages one at a time and timed at a few different intervals (100 ms is what I'm using this instant).

Clock is 4mHz, bus speed is 125kbit/sec, and I've tried these 2 settings for the BRGCON registers (shooting for 125k bus speed, 75% sp, sjw = 1):
BRGCON1 = 0x01
BRGCON2 = 0x91
BRGCON3 = 0x01

and
BRGCON1 = 0x00
BRGCON2 = 0xAC
BRGCON3 = 0x03
again, both seem to work for xmit, neither for receive.

thanks for your help!

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

See threads like this one and the links within it:
http://www.ccsinfo.com/forum/viewtopic.php?t=20387

Also try the code for loopback mode, as described in one
of the links.

Joules · Joined: 02 Mar 2006 Posts: 9

PCM programmer, thanks so much!

problem was the extended ID, looks like others had the same problem, so I don't feel so stupid.

Thanks again.