FDCAN H7 BRS failure with Kvaser Leaf 3

[LCE]

Heyho,

after some *** CAN beginner mistakes on my side, I got the FDCAN BRS 8 Mbit working.

Or so I thought. It's only working between my custom boards, as I found out after connecting a Kvaser Leaf v3.

With the Kvaser (directly connected to the board's D-sub, termination on, signals on the scope look good (enough)) and BRS on, it only works with max 2 Mbit, and only if the Kvaser's bit timing is set below 70% sampling point.

So far I played with changes to TDC, sampling point, SJW, and all bit timings (checked the Kvaser timing website).

Any ideas welcome!

[mƎALLEm]

So it's a "Kvaser" issue as FDCAN BRS 8 Mbit is working between your custom boards.

Did you remove the terminating resistor inside that Kvaser device? you need only two terminating resistors on the CAN lines.

[LCE]

Thanks for the quick answer!

I only have the Kvaser connected to one of my boards.
The termination resistor is switchable on my boards (with an isolated low capacitance opto relay).

[mƎALLEm]

Do you confirm FDCAN is working well between the boards without that kvaser device?

[LCE]

> Do you confirm FDCAN is working well between the boards without that kvaser device?

Yes, at all bit rates.

Scope confirms bit timings.

I thought that the Kvaser stuff - coming from the market leader (I think) - is the impeccable reference.

So maybe I got something wrong?

Here's the CAN register settings for 8M (hex):

(for the segment times below the complete register, e.g. DTSEG1, the "+1" is already included)

FDCAN 1->
Clock = 80.000 MHz - PLL 1 Q
CREL = 32141218
ENDN = 87654321
DBTP = 00800521
        TDC = 1
        DBRP   = 1
        DTSEG1 = 6
        DTSEG2 = 3
        DSJW   = 2
NBTP = 24008A13
        NBRP   = 1
        NTSEG1 = 139
        NTSEG2 = 20
        NSJW   = 19
TEST = 00000080
RWD  = 00000000
CCCR = 00004300
        INIT = 0
        CCE  = 0
        ASM  = 0
        CSA  = 0
        CSR  = 0
        MON  = 0
        DAR  = 0
        TEST = 0
        FDOE = 1
        BRSE = 1
        PXHD = 0
        EFBI = 0
        TXP  = 1
        NISO = 0
TSCC = 00000001
TSCV = 0000BA51
TOCC = 0000FFFF
TOCV = 0000FFFF
ECR  = 00000000
PSR  = 0000070F
GFC  = 00000007

[mƎALLEm]

---

@LCE wrote:

> Do you confirm FDCAN is working well between the boards without that kvaser device?

Yes, at all bit rates.

---

So that's not a STM32 issue, that's "kvaser" related one which I cannot help you on that.

Check again your kvaser device config, your wiring etc ..

[mƎALLEm]

A question: What is the clock source of PLL1Q? HSE?

Are you using a crystal?

If not, please use HSE as source clock for PLL1Q and use crystal (XTAL) or crystal oscillator (XO).

[LCE]

HSE, ultra stable 10 ppm crystal

PTP running on that successfully, lots of timing relevant stuff in that application.

[mƎALLEm]

According to "Kvaser Leaf v3" specification, it can reach up to 8Mbit/s

So it should work.

Still not clear about the terminating resistor inside that device. Ensure that -if available- the internal terminating resistor on that kvaser device is disconnected.

What about the configuration of the tool: the bitrate the mode.. etc ?

Or raise a support ticket to kvaser over this link: https://kvaser.com/support/

[LCE]

> terminating resistor inside that device

I don't want to fiddle with the Kvaser hardware.
And as I said: there's a switchable terminating resistor on my board, and when that one is turned off, not even non-BRS is working.