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TMS320F28379D: SYSCONFIG CAN Bit Rate GUI does Not Generate Code Correctly For Parameters Specified in Time Quanta

Kier
Mastermind 9640 points

Part Number: TMS320F28379D
Other Parts Discussed in Thread: SYSCONFIG, C2000WARE

Hello,

If I select the following 1Mbps configuration in SYSCONFIG:

...the following code is generated:

CAN_setBitTiming(MAIN_CAN_BASE, 7, 0, 15, 7, 2);

There's a direct numerical mapping between the GUI contents and the arguments to CAN_setBitTiming(). Unfortunately this function updates the register with the arguments directly which means that the Tq values are not converted to the register values correctly.

For example,  "(Re)Synchronization Jump Width (Tq)" = 2 should set CAN_BTR.SJW = 1 since actual SJW = CAN_BTR.SJW + 1.

The purpose of the SYSCONFIG (I think) is to abstract the design parameters, in this case Tq, from the register contents but this does not seem to be the case for CAN bit timing.

  • 0
    TI__Guru 52080 points

    Kier,

    You are 100% correct with the purpose of SysConfig. I am looping in the MCAN experts. 

    SysConfig and driverlib should work together to update the registers correctly.

    can you review how the values are calculated in SysConfig, how they are generated in the CODE and how driverlib uses these values to update the registers? 

     

    Thank you,
    Nima Eskandari
    C2000 Application Manager

  • 0 in reply to Nima Eskandari
    TI__Guru 52080 points

    can you also verify this alongside Sahil?

  • 0 in reply to Nima Eskandari
    Mastermind 9640 points

    Many thanks everyone.

    Perhaps the SysConfig GUI auto calculation mode should use the same formulae and inputs as Hareesh's Excel calculator (https://www.ti.com/lit/pdf/SPRAC35)?

    Just a suggestion.

  • 0 in reply to Kier
    TI__Guru 52080 points

    Agreed. I will see if we can provide a fix for you quickly as well.

  • 0 in reply to Nima Eskandari
    TI__Guru 52080 points

    did you take a look at this? we can provide a fix in the next C2000WARE release.

  • 0 in reply to Nima Eskandari
    TI__Guru 52080 points

    , do we have an update on this?

  • 0
    TI__Expert 6035 points

    Kier, 

    I apologise for the late response.

    The values that can be seen as parameters to the function, are actually corrected in order to be fed to the registers directly. 

    The issue here is with the naming of the fields. In this specific example, (Re)Synchronization Jump Width (Tq) is actually 3, which in turn sets CAN_BTR.SJW to 2. 

    Thanks for pointing this out. I will update Sysconfig so that the fields will read the actual values, and not the corrected values, which in turn are the parameters to the function CAN_setBitTiming().

    Thanks.

  • 0 in reply to Sahil Deshpande
    Mastermind 9640 points

    Sahil,

    Thanks for the reply.

    Sahil Deshpande said:
    The values that can be seen as parameters to the function, are actually corrected in order to be fed to the registers directly. 

    If by "corrected" you mean calculated by SYSCONFIG from Bit Rate and SYSCLK to be suitable for CAN_setBitTiming() then yes, that's understood.

    Sahil Deshpande said:
    The issue here is with the naming of the fields.

    I don't agree, it's the values for some of the fields which are incorrect. You could keep the field names the same but just add 1 to some of the values displayed and everything would be fine. For example, if SYSCONFIG displayed the following purple values instead (with code generation unchanged of course), I wouldn't have raised an issue because the value in units of Time Quanta would be correct:

    But, as mentioned in the original discussion, this is probably not the best set of fields to present to the SYSCONFG user in auto calculation mode anyway. The TRM CAN section directs the reader to https://www.ti.com/lit/an/sprac35/sprac35.pdf. The associated Excel calculation tool has the following input parameters:

    Bit rate (kilobits/sec)
    Bus length (m)
    Extra propagation delay (us)
    CAN clock frequency (MHz)

    Why not consider the same input parameters for SYSCONFIG in auto calculation mode? i.e. when "Use Calculated Values..." is selected. Here SYSCONFIG could add real value where the environment of the CAN controller is a factor in the bit timing selection.

    Please also consider adding "Sample Point" as a read only field in SYSCONFIG calculated from the inputs.

    Thank you.

    Kier.

  • +1 in reply to Kier
    TI__Expert 6035 points

    Kier,

    Kier said:
    it's the values for some of the fields which are incorrect. You could keep the field names the same but just add 1 to some of the values displayed

    We are in complete agreement here. What I suggested instead was to rename the fields to "Programmed TSEG1" and "Programmed TSEG2". The alternative is what you suggested and that is arguably better. I will push that change.

    Kier said:
    Why not consider the same input parameters for SYSCONFIG in auto calculation mode? i.e. when "Use Calculated Values..." is selected. Here SYSCONFIG could add real value where the environment of the CAN controller is a factor in the bit timing selection.

    This is an excellent point, thanks for bringing this up. We will review this as a team and get it implemented.

    Thanks.

  • 0 in reply to Sahil Deshpande
    Mastermind 9640 points

    That's great. Thank you very much.