18F26K80 CAN bit rates 250 and 500

[oxo]

Hi all,

I have this chip working at 125kbit/s, but no matter what I try, I can't get it to work at 250 or 500 kbit/s.

I have a 16 MHz xtal, ad 4x pll, so clock is 64 MHz.

Settings for 125 kbit:

CAN_BRG_PRESCALAR 15
CAN_BRG_PROPAGATION_TIME 2
CAN_BRG_PHASE_SEGMENT_1 7
CAN_BRG_PHASE_SEGMENT_2 3

Can anyone share their working settings for 250 and 500 please?

[oxo]

OK, so now i have settings for 250kbit, #

I dropped the pll, so clock is now 16 MHz.

[temtronic]

I don't have that PIC but general comments...

It could be a 'bug' in your compiler version, that's why it's important to tell us what you're running.

Also, dump out the listing and confirm the correct register is being set/cleared according to the PICs datasheet.

Since you're only changing...#define CAN_BRG_PRESCALAR 1 ...
it should be easy to find and see what's happening.

It might be that ' CAN_BRG_PRESCALAR ' is being changed twice unknown to you, from 'extra' code that shouldn't be there....

hth
jay

[oxo]

Compiler 5.012

And all the code is from the j1939 example of ccs

[PCM programmer]

[newguy]

Further to what PCM has posted, I had a lot of trouble with the CCS CAN functions with later version 4 compilers (4.100+) and dsPICs. I ended up having to completely set up the CAN registers myself. I have no experience with the version 5 compiler yet.

[oxo]

[Ttelmah]

Other thing to remember is that as frequencies get higher, so do the requirements to keep bus capacitance's low, terminate properly, etc. etc..

Best Wishes