topic Re: MPC574x CANFD @4MBPS in MPC5xxx

MPC574x CANFD @4MBPS

akshay_hv — Tue, 23 May 2017 12:23:11 GMT

Hello,

I have been trying to test the CANFD with different speeds. currently I am able to work the CANFD at 2 MBPS. The register initialization is as follows.
the Baudrate resgisters are configured to 500 kbps and Data rate registers are configured with 2 MBPS. The fcanclk is 40Mhz.

lp_FlexCan_fd->CTRL1.B.PRESDIV = 0x03;
lp_FlexCan_fd->CTRL1.B.PROPSEG = 0x07;
lp_FlexCan_fd->CTRL1.B.PSEG1 = 0x05;
lp_FlexCan_fd->CTRL1.B.PSEG2 = 0x04;
lp_FlexCan_fd->CTRL1.B.RJW = 0x02;
lp_FlexCan_fd->FDCBT.B.FPRESDIV = 0x01 ;
lp_FlexCan_fd->FDCBT.B.FPROPSEG = 0x03 ;
lp_FlexCan_fd->FDCBT.B.FPSEG1 = 0x02 ;
lp_FlexCan_fd->FDCBT.B.FPSEG2 = 0x02 ;
lp_FlexCan_fd->FDCBT.B.FRJW = 0x02 ;

I want to test the CANFD with 4 MBPS so ... I did the calculations using this algorithms by keeping PRESDIV to 0 and I got the N0Tq as 10. And I kept the initialzation as below

lp_FlexCan_fd->CTRL1.B.PRESDIV = 0x03;
lp_FlexCan_fd->CTRL1.B.PROPSEG = 0x07;
lp_FlexCan_fd->CTRL1.B.PSEG1 = 0x05;
lp_FlexCan_fd->CTRL1.B.PSEG2 = 0x04;
lp_FlexCan_fd->CTRL1.B.RJW = 0x02;
lp_FlexCan_fd->FDCBT.B.FPRESDIV = 0x00;
lp_FlexCan_fd->FDCBT.B.FPROPSEG = 0x03;
lp_FlexCan_fd->FDCBT.B.FPSEG1 = 0x02;
lp_FlexCan_fd->FDCBT.B.FPSEG2 = 0x02;
lp_FlexCan_fd->FDCBT.B.FRJW = 0x02;

But this configuration is not working for me.. So please have look into my intialization and correct me if I am doing anything wrong in here

And I would be nice if you can clarify me how the PROPSEG, PSEG1,PSEG2 is calculated once we get the N0Tq = 10,12..... etc

Re: MPC574x CANFD @4MBPS

PetrS — Tue, 23 May 2017 13:18:58 GMT

Hi,

Do you have Transceiver Delay Compensation enabled (FDCTRL[TDCEN]=1)?

If not (FDCTRL[TDCEN]=0) then the transceiver loop delay time could be longer than the actual sample point delay (200ns with your setting). The FlexCAN then detect a bit error in data phase.

That’s why the Secondary Sample Point is defined and used when TDC is enabled.

If TDC is used, what is FDCTRL[TDCOFF] setting in fact? What is read from FDCTRL[TDCVAL]?

Theoretically the TDCOFF should be set to the middle of the data bit time, so

TDCOFF = bit_time/2 * PEclock = 250ns/2 * 40MHz = 5.

BR, Petr

Re: MPC574x CANFD @4MBPS

akshay_hv — Tue, 23 May 2017 13:56:27 GMT

Hello Petr,

That really was helpful. Thanks for that assistance.

I have a further question. How to configure the data rate to 3Mbps..

I tried calculating this formulas.. But its not working for me..

I would really appreciate if you can help me on this. to initlaize my Data rate registers.

regards

Akshay H V

Re: MPC574x CANFD @4MBPS

PetrS — Tue, 23 May 2017 14:08:30 GMT

Hi Akshay,

from the formulas, you gave, you can get

(PRESDIV+1) * No_Tq = f_CANCLK / BR

Then assuming PRESDIV and No_Tqare integer values only, there is no possible setting for given PE clock and baudrate.

Different PE clock has to be used.

BR, Petr

Re: MPC574x CANFD @4MBPS

akshay_hv — Tue, 23 May 2017 14:15:31 GMT

Hello Petr,

Just for my understanding you are mentioning that the fcanclk has to be

changes from current 40Mhz.. to something else.. to achieve the 3 MBPS

data rate..??

Regards

Akshay H V

SWP FBL developer

Interior-Body and Security

Re: MPC574x CANFD @4MBPS

PetrS — Wed, 24 May 2017 06:01:05 GMT

Yes, you are right.

BR, Petr