clock configuration for CAN on Launchpad XL2

user4125449

Other Parts Discussed in Thread: HALCOGEN

Hello,

I am using a Launchpad XL2 and I am trying to configure CAN. As clock configuration I am using the default values from Halcogen for my processor (RM46L852PGE).I did configure a bitrate of 50 kBit with Halcogen. I am sending CAN Tx frames and I am measuring these frames on a scope. I see the bitclock is not as expected 50kBit but around 36kBit. It seems as if the clock input for the CAN modules is somehow slower than expected from the processor. The clock input for CAN is VCLKA1 and the input for VCLKA1 is VCLK. (Everything as generated by HalcoGen).

Any ideas?

best regards

Matthias

over 9 years ago

0 Bob Crosby over 9 years ago

TI__Guru 72500 points

So using the default settings, but changing the default baud rate from 500Kb to 50Kb your settings look like these?

0 user4125449 over 9 years ago in reply to Bob Crosby

Intellectual 330 points

Hi Bob,

yes that's true. And CAN is working fine when I am using the external clock as reference for CAN and not VCLKA1.

best

Matthias

0 Bob Crosby over 9 years ago in reply to user4125449

TI__Guru 72500 points

Would you please attach your .hcg file?

0 user4125449 over 9 years ago in reply to Bob Crosby

Intellectual 330 points

sure, no problem1680.hcg_file_as_test.hcg.txt

0 user4125449 over 9 years ago in reply to user4125449

Intellectual 330 points

I also did debug the problem on a brand new launchpad and its gone, no problems anymore with the default HalcoGen code. But what hardware error on the Launchpad could lead to such a strange effects?

0 Bob Crosby over 9 years ago in reply to user4125449

TI__Guru 72500 points

If you were using the OSCIN clock to run the CAN module and there was an oscillator fault (problem with the connection to the crystal) the device would run at the HFLPO frequency. That frequency varies, but is generally between 10 and 12MHz. An 11Mhz clock (instead of the expected 16MHz) would give you the 36K baud instead of the expected 50K baud. The oscillator fault flag is bit 0 (OSCFAIL) in the GLBSTAT register (0xFFFFFFEC).

0 user4125449 over 9 years ago in reply to Bob Crosby

Intellectual 330 points

Hi,

With the OCSIN as clock source for the CAN module the CAN is working fine. I am having the problem when I am using the (HalcoGen) default VCLK as source.

best
Matthias

0 Bob Crosby over 9 years ago in reply to user4125449

TI__Guru 72500 points

OK, I am at a loss. If you want to look further, I suggest you output VCLK on the ECLK pin (J10-19) . You can do this in HALCoGen:

Check the ECLK frequency on a scope. That way we can determine if it is a PLL/CLK problem or a CAN module problem.

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clock configuration for CAN on Launchpad XL2