AWR1843: DCAN sample point configuration

Hi,

Please give us some time to check with the design team

thank you
Cesar

Hi Cesar,

Thanks for help. Hope this topic get solved ASAP!

sincerely,

EricHuang 

I have contacted the sw development team.

Will get back to you as soon as I have an updated

thank you

Cesar

Hi,

Here is the information I have received from the sw development team.

Below are the calculation for the 20MHz CAN Clock.

CAN clock (can_clk)=20Mhz

time Quanta(tq)=1 / can_clk =1/20M = 50ns

Eg: bit rate =500kbps

bit time=1/500kbps=2us

no of tq=2us/50ns=40tq.

Configure TSEG1 and TSEG2 to set sampling at 80% of a bit time.

(Tsync_seg+TSEG1) / (Tsync_seg+TSEG1+TSEG2) =80%

as we calculated above: bit time = Tsync_seg+TSEG1+TSEG2=40tq

so , (1+TSEG1)/(40)=80%

TSEG1=32-1=31

TSEG2 = 8

Tsync_seg=1(fixed)

TSEG1=31

TSEG2=8

Thank you

Cesar

Hi Cesar,

I browse the file "AWR18_16_14_68_Tech_Reference_Manual".

The file shows (fig.1) that the valid value of TSEG1 = 1~15, TSEG2 = 0~7.

I am confused the configuration you mentioned above was reasonable because the TSEG1 and TSEG2 both exceed the valid value.

Moreover, the parameters I set are CAN clock = 20Mhz, baudrate = 500kbps, propagation delay = 700ns, sample point = 70% (shown as fig.2).

How can I set sample point I want (e.g. 80%, 87.5%) under the condition CAN clock = 20Mhz, baudrate = 500kbps. 

Is propagation delay related to sample point? If so, what is the formula or transformation between them.

Thank you!

Sincerely,

EricHuang

                                            fig.1

                                           fig.2

I also configure sample point according to the method you mentioned above.

I try three settings in total which are shown below:

====================Set 1====================

baudRatePrescaler =  4;

timeSegment1 = 7;

timeSegment2 = 2;

baudRatePrescalerExt = 0;

syncJumpWidth  =  2;

Sample point in theory (fig.1) = 80%. However, measured by instrument (CANoe) is 75%.

         fig.1: Sample point configuration in theory

              fig.2: Configuration sample point in code

====================Set 2====================

baudRatePrescaler =  2;

timeSegment1 = 16;

timeSegment2 = 3;

baudRatePrescalerExt = 0;

syncJumpWidth  =  2;

Sample point in theory (fig.3) = 85%. However, measured by instrument (CANoe) is 87.5%.

          fig.3: Sample point configuration in theory

             fig.4: Configuration sample point in code

====================Set 3====================

baudRatePrescaler =  5;

timeSegment1 = 6;

timeSegment2 = 1;

baudRatePrescalerExt = 0;

syncJumpWidth  =  2;

Sample point in theory (fig.5) = 87.5%. Measured by instrument (CANoe) is 87.5%.

         fig.5: Sample point configuration in theory

            fig.6: Configuration dample point in code

============================================

I want to control sample point between 75~87.5%. Therefore, the safe value I desire is 80%.

I try the way you mentioned above to configure sample point. However, the sample point that instrument measured is either 75% or 87.5%.

I have no idea now, do I misunderstand something or is there any constraint on device?

Thank you!

Sincerely,

EricHuang  

Hi,

I am still working on this issue.

Will provide you feedback as soon as possible

thank you

cesar