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TMS320F28379D: Can F28379 read SSI Encoder?

Hakan B
Expert 1100 points
Part Number: TMS320F28379D

Hello everyone,

As far as I know, F28379 can read BISS encoders and BISS interface is a derivative of SSI interface. So, can F28379 read SSI encoders as well? 

Thanks in advance,

Hakan

  • 0
    TI__Mastermind 24095 points

    Hakan,

    BiSS-C and SSI digital formats are similar, though BiSS-C has several additional features. But they are not fully compatible to each other.
    We do not have a library for SSI on F28379, but we do support BiSS-C - you can refer to position manager, if you've not already done so.

    -Bharathi.

  • 0 in reply to Subrahmanya
    Expert 1100 points
    Dear Bharathi,

    Thank you for the answer. Although BISS-C and SSI are very similar, I couldn't achieve to read SSI encoder using position manager libraries. It is because of clock timing difference between encoder and SPI lines. It has been mentioned in this topic.

    e2e.ti.com/.../628358

    So, in order to use CLB for SSI encoder reading, we need a specific SSI library (like the BISS library in the position manager) or a generic CLB library that we can program. In the link above, you told that you were working on a specific SSI library almost 6 months ago. What is the progress of it? When do you plan to release the new library?

    Hakan
  • 0 in reply to Hakan B
    TI__Mastermind 24095 points

    Hakan,

    The Position Manager library addresses BiSS-C protocol. Though BiSS-C and SSI are similar, same library will not work for both.
    Currently, there is no plan to release SSI.

    Thanks for linking the previous post - as I already said in the post you've mentioned,
    Product updates will be communicated and will available at www.ti.com/c2000drives. 

    -Bharathi.

  • 0 in reply to Subrahmanya
    Expert 1100 points
    Bharathi,

    In the mentioned post you were saying "We are working on a separate library for SSI interface. Please watch the www.ti.com/c2000drives page for updates."

    Now you are saying "Currently, there is no plan to release SSI." Don't they conflict each other?

    Nevertheless, I can not understand why TI does not support SSI in F28379. As far as I know, the main difference between F28377 (which was the top end of Delfino family) and F28379 (new king) is the absolute encoder reading capability.In older motor driver designs we were using a DSP + a small FPGA for absolute encoder interface, but now we can use only the F28379. That is the biggest advantage of F28379. But TI loses this advantage by NOT supporting a common used, well-known encoder interface like SSI. The thing is, TI can support SSI with a very little changes of existing BISS-C library (no HW change is required). Even TI does not want to do it, it can simply make BISS-C or F2837xD_Clb_drivers public, so the community can implement their own SSI library.

    Bharathi, could you please deliver my message to the decision-makers, maybe they can change their minds.


    I hope you do not fall behind of your competitors: www.youtube.com/watch

    Regards,
    Hakan
  • 0 in reply to Hakan B
    TI__Mastermind 24095 points
    Hi Hakan,

    BiSS-C and other interface protocols are delivered as compiled libraries - so, it's not possible to tweak the library to support for SSI by the user directly. What you said is absolutely correct - F28379 has capability to support SSI, not just SSI but several other encoder protocols as well. We prioritized the development of these interfaces based on the need and opportunities. We are certainly aware and investigating the possibility of giving open source drivers for CLB to let customers develop their own custom implementation. Any updates/releases related this will be available on the links I referred above. Thanks a lot for your valuable inputs.

    -Bharathi.