CAN FD does not work correct after 2.5Mbit

[apeter]

Hello everyone,

I am  currently using a custom board where a CYT4BB5CEBES and a TLE9471ES is placed on it.

For testing purposes I have a Y-Cable which uses 2 CAN FD Controllers to communicate against each other like a selftest. On each end there is the CAN termination (Only 2 used).

This works fine with CAN FD and for example 2.5Mbit (Checked with CanEasy) but when I try to for example send over 4Mbit i only get a message from 1 CAN FD Controller  and when I try 5Mbit settings no CAN FD Controller works.

So my question now is, if I have a clock frequency of 40MHz and following settings:

.prescaler = 1u - 1u,
.timeSegment1 = 5u - 1u,
.timeSegment2 = 2u - 1u,
.syncJumpWidth = 2u - 1u,

It should output 5MBit with 75% sample point and 25% Sync jump width. Can you please confirm if this setting is correct?

And if not could you please explain where I am wrong here and tell me the correct values for it.

PS: I have also checked TX messages on an oscilloscope and cyclic messages are working for 2,5Mbit but not for 5Mbit. I also get an TxErr in the CanEasy application.

Would appreciate any help.

Best regards,
apeter

[Apurva_S]

Hi @apeter 

• The hardware setup described by you is not completely clear to us. Could you please elaborate more about the hardware setup? It would be helpful if you could provide a high level block diagram for your system.
• You could try increasing the clock frequency and do a quick check if that works. You could try increasing the freq to 80MHz.
• Please check if the CAN Transceiver supports the required frequency.
• Could you please share the register settings for Nominal Bit Rate and Data Bit Rate configuration.

Regards.

[apeter]

Hi @Apurva_S ,

Please find here the high level block diagram.
I hope this helps to know what I mean.
If you want to know something else just ask then i can elaborate more.

My Goal is just to send a CANFD message with 5Mbit with a certain data pattern from CAN0_1 to CAN1_0 and from CAN1_0 to CAN0_1 and check if it was possible to send or it run into errors and counter them for an EMC test.

This setup works with 2,5Mbit but I do not know why it does not for 5Mbit. As already mentionend I got 2 TX signals but afterwards just got TXerr from CAN bus.

I have also tried to increase clock frequency to 80MHz but it had the same effect. 2,5Mbit worked and 5Mbit doesn't.

TLE9471ES and TJA1044 does support 5Mbit.

Please find register settings below (40MHz):

CAN_0_1 Nominal Bit Rate (0x4052021C)

0000 0010 0000 1001 0000 0100 0000 0001

NTSEG2 = 1
NTSEG1 = 4
NBRP = 9
NSJW = 1

CAN0_1 Data Bit Rate (0x4052020C)

with 2,5Mbit: 0000 0000 0000 0001 0000 0100 0001 0001

DSJW = 1
DTSEG2 = 1
DTSEG1 = 4
DBRP = 1
TDC = 0

with 5Mbit: 0000 0000 0000 0000 0000 0100 0001 0001

DSJW = 1
DTSEG2 = 1
DTSEG1 = 4
DBRP = 0
TDC = 0

CAN_1_0 Nominal Bit Rate (0x4054001C)

0000 0010 0000 1001 0000 0100 0000 0001
NTSEG2 = 1
NTSEG1 = 4
NBRP = 9
NSJW = 1

CAN1_0 Data Bit Rate (0x4054000C)

with 2,5Mbit: 0000 0000 0000 0001 0000 0100 0001 0001

DSJW = 1
DTSEG2 = 1
DTSEG1 = 4
DBRP = 1
TDC = 0

with 5Mbit: 0000 0000 0000 0000 0000 0100 0001 0001

DSJW = 1
DTSEG2 = 1
DTSEG1 = 4
DBRP = 0
TDC = 0

Thank you and best regards,
apeter

[apeter · Accepted solution]

Hi @Apurva_S ,

We will try with an EVAL Board to achieve the 5MBit and will get back to you.
When this will work then we might have a HW problem on our custom board.

Thank you and best regards,
apeter