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Cyclone Max mini-20/mini-10 cable connection required for programming?!?!
Tommy B. Feb 19, 2015 at 09:18 AM (09:18 hours)
Staff: Takao Y.

  • Strange issue:
    If I connect my Cyclone Max to my board using the 20 pin standard ribbon cable to SWD/JTAG adapter board to either the mini-20 or mini-10 connections, I can program just fine. If I connect the standard 20 pin ribbon cable directly to my board (no adapter, no mini ribbon cable), I get an immediate programming error. Verified connections a hundred times. Using SWD. Very strange.

    On top of that, if I have the standard ribbon cable connected to my board, then plug in the adapter board and the mini-20 connection (free-hanging, not connected to anything), it works! Literally just the presence of this cable makes it start working!

    I've scoped the traces and don't see any considerable difference between the two. I was thinking the reflections could have something to do with it.

    In the meantime, I can get my production environment up by leaving the mini-20 cable and adapter connected and free-floating but I would like to understand why this is happening.


  • Greetings,

    That is because the adapter board is wired up correctly where it shorts TDO to TMS for SWD. The 20 pin standard is the same as 20 pin mini for JTAG. The 3-pin jumper on the adapter is there for a reason.

    If you want to use the standard 20 pin, then short TMS (pin 7) and TDO (pin 13) for SWD and you will not need the adapter board anymore. Then remove this short for JTAG communication.

    Takao Yamada

    • My apologies, I did do this short on the standard ribbon cable

      • Greetings,

        So is everything working for you now?

        Takao Yamada

  • No, I had those lines tied all along and getting the above mentioned issue

  • Greetings,

    I do not understand the statement "if I have the standard ribbon cable connected to my board, then plug in the adapter board and the mini-20 connection (free-hanging, not connected to anything), it works! "

    Explain to me what is connected from the cyclone to the board.

    Normal connection is as follows:

    Cyclone Max -> Standard 20 -> Adapter board SWD -> 20 or 10 pin mini -> Target board.

    How is your setup different that makes it work?

    Takao Yamada

  • Starting from the Cyclone Max, I have a 20 pin ribbon cable connected to it that has a total of three 20 pin connectors (one connected to the Cyclone Max), one in the middle of the cable, one at the end of the cable).  This cable has the TDO and TMS wires shorted on it (verified continuity).  The middle connector has a header on it where I am routing power, ground, SWD data and clock, and reset to my target board.  With this configuration, I get immediate programming errors.  If I plug the connector at the end of the cable into the adapter board with the mini-20 cable connected (but not connected to anything on the other end), I can program just fine

    • It would be ideal to show you pictures or even a video of my setup

  • Greetings,

    No need for pictures. I now understand what it looks like.

    Any customer who customize their ribbon cables I always suggest shielding their cables to reduce noise.

    By adding the adapter and extra ribbon cable, you are extending the length and resistance to the wiring like an antenna.

    Have you tried connecting to the target towards the end of the cable instead of the middle? Have you tried decreasing the debug shift speed/frequency to see if the problem is just communication is too fast?

    Takao Yamada

  • I have tried both the middle and end of the cable, but I have not tried changing the shift speed/frequency.  Will give that a shot and report back.  Thank you

  • Greetings,

    Any update on this?

    Takao Yamada

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