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Fast Serial Interface

Balaji Appadurai45
Prodigy 200 points
Other Parts Discussed in Thread: TMS320F28388D, TMDSFSIADAPEVM

We are also exploring Fast Serial Interface for the board to board communication . I’m referring to the document “Using the Fast Serial Interface (FSI) With Multiple Devices in an Application” to understand FSI.

Star Topology is preferred over Daisy Chain(refer below picture), TMS320F28388D Controller is capable of supporting 8 receivers and 2 transmitter. However 2 or 3 Nodes and 1 lead are needed as per our requirements. Kindly request you to address the following queries on FSI

 

Questions:

1) Lead/Host should have number of transmitter connectors which should be based on number of nodes and they get shorted internally as shown in the below pictures. Is my understanding correct?

2) What is the advantage of FSI over SPI?

3) How much distance does FSI can support?

4) How is the immunity level of FSI during high frequency data transmission?

5) How is the delay managed when we use Isolator & LVDS?

  

                  

  • 0
    TI__Mastermind 47047 points

    HI Balaji,

    Hi I am looping someone from our C2000 team as they will be able to better support on information about FSI.

    Best,

    Parker Dodson

  • 0 in reply to Parker Dodson
    TI__Mastermind 41726 points

    HI Balaji,

    Balaji Appadurai45 said:
    Star Topology is preferred over Daisy Chain(refer below picture), TMS320F28388D Controller is capable of supporting 8 receivers and 2 transmitter. However 2 or 3 Nodes and 1 lead are needed as per our requirements. Kindly request you to address the following queries on FSI

    You may also be interested in considering a bus-style design with FSI. While we haven't tested the topology ourselves we've noticed it seems possible by leveraging M-LVDS devices, which enable multi-drop/point typologies. See https://www.ti.com/lit/slla108 for more info on M-LVDS device capabilities.

    Balaji Appadurai45 said:
    1) Lead/Host should have number of transmitter connectors which should be based on number of nodes and they get shorted internally as shown in the below pictures. Is my understanding correct?

    There would be a number of ways the TX connections from the Lead/Host to the different Node devices can be designed. What you have shown is one way that could be made to work, but signal integrity considerations need to be made and the FSI clock speed may have some limitations. It may be necessary to buffer the signals to the nodes depending on desired FSI speed, cable distance, etc.

    Balaji Appadurai45 said:
    2) What is the advantage of FSI over SPI?

    There are quite a few advantages over SPI. Overall throughput can be higher (200Mbps is possible), FSI is more ideal for communicating over isolation, HW implemented CRC, and more. I'd suggest reviewing section 5.3 Distributed Real-Time Control Across an Isolation Boundary in the document below, it gives a good overview.

    https://www.ti.com/lit/spracn0

    Balaji Appadurai45 said:
    3) How much distance does FSI can support?

    We have some cable length data tested with the TMDSFSIADAPEVM hardware. 10M cable was achievable in some cases, see the User's Guide below for more details. We don't have Star connection data available unfortunately.

    https://www.ti.com/lit/swru555

    Balaji Appadurai45 said:
    4) How is the immunity level of FSI during high frequency data transmission?

    It is quite good, especially when you properly leverage differential devices (RS-485/422 or LVDS) for the physical layer. There will of course be dependence on the overall noise in your system environment. You may like to reference the "Distributed multi-axis servo drive over fast serial interface (FSI) reference design" linked below to see FSI being used in a more real application.

    https://www.ti.com/tool/TIDM-02006

    Balaji Appadurai45 said:
    5) How is the delay managed when we use Isolator & LVDS?

    The FSI receiver modules have integrated delay line control feature to compensate for channel-to-channel skew on any of the FSI data/clock signals. See block diagram and App Note below for more details.

    https://www.ti.com/lit/spracj9

    Best,

    Kevin