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TINA/Spice/PROCESSOR-SDK-AM335X: PTO solution questions

yude zhang9
Prodigy 180 points

Part Number: PROCESSOR-SDK-AM335X
Other Parts Discussed in Thread: TINA-TI,

Tool/software: TINA-TI or Spice Models

i am working to desing a PTO soluton on PRU. FAE give me a pto soluton pdf, but i don't understand the Pulse_position_raster and the Dma_slot_per_sec meaning?

www.ti.com/.../tidu707.pdf

  • 0
    TI__Guru**** 393215 points
    The factory team have been notified. They will respond here.
  • 0 in reply to Biser Gatchev-XID
    Prodigy 180 points

    Haven't receive their reply! Could you urge them? Our project need it at once! 

  • 0 in reply to yude zhang9
    TI__Expert 5490 points
    We look into your question and provide a respond soon.
  • 0
    TI__Expert 5490 points
    Hi,

    Let me give some further information to address your question:

    1) The PRU PTO implementation is operating with a 50ns pulse-to-edge calculation, which means the PRU firmware can decide every 50ns if a pulse-edge needs to get generated.
    2) One complete pulse can be on a 100ns pulse position raster (referred in the documentation as Pulse_position_raster) – this is basically the pulse granularity. Note also that in the TI design documentation has an errata, the parameter is not in micro-second but Hz.
    3) Only one pulse can occur within 1us, which derives the maximum pulse frequency of 1MHz.
    4) The smallest segment of an PTO profile is 1us, i.e. if you plan to create an S-curve acceleration profile then the smallest segment is 1 us.
    5) The Dma_slot_per_sec is used for ARM calculation for this smallest segment

    You can contact your FAE to get further information about the ARM based source code.
  • 0 in reply to Thomas Mauer
    Prodigy 180 points
    Hi， thanks Thomas. i still have a question, for the acceleartion stage. I don't understand why the acceleartion is 1. i try to use the code to do inverse. The compare speed is add 1 pre 1us. How to change it to 2000step/s2?
  • 0 in reply to Thomas Mauer
    Prodigy 180 points

    i still  have a last question. The compare value is 500 000 000. The next consumption are my personal view. i want you to check it right or not.

    =====

    The 1 step is divded as 1 000 000 000 small steps. As the PTO is 50%, so the compare value is half of this value.

    If this consumption is right, does it means that if i change the PTO one block time from 50ns to 100ns(as we want to use 2 PTOs), this value can still keep the same?

    If not, how to change the compare value? Or does this value is define by yourself, it has no relation ship with other?

  • 0
    Prodigy 180 points

    Part Number: PROCESSOR-SDK-AM335X

    Hi,

        FAE give me a reffence for PRU running PTO.www.ti.com/.../tidu707.pdf  In this solution, i have a question. How to caculate the compare value?

    In your example, the value is 500 000 000. In my view, i think it dived 1 step into 1 000 000 000 small steps. As pto is 50%, so the compare value is half of it.

    Is my understand correct or not?

    For our project, we want to run 2 PTOs on one core, so the block time will become 100ns. Does this change will affect the compare vlaue?

  • 0 in reply to yude zhang9
    TI__Expert 5490 points
    The TI design PTO implementation has been developed to support one PTO per one PRU.
  • 0 in reply to Thomas Mauer
    Prodigy 180 points

    ok. i don't understand the compare vlaue 's caculation method. Could you expain it?