Using JTAG with the Duet Wifi



  • Hello everyone,
    I am starting a small coding project using my duet wifi and intended to connect a J-Link to the JTAG port of the duet wifi to do some debugging.

    I'm using a Duet 2 Wifi v1.02

    Looking through the schematic I found that the pullups for the JTAG lines are not populated on the production boards, and also that one of the JTAG pins is reassigned to do VSSA sensing.

    My PCB and schematic knowledge is limited, do I need to make any changes to the board to be able to use a JTAG probe with it? I imagine I'll need those pullup resistors, but I'm also worried about the VSSA sensing bit (as I understand VSSA will be near ground level) and don't want to fry anything.

    If you can spare the time, I'd appreciate some guidance.

    Bests,

    aMpeX

    edit: After doing some more digging I found that TCK(VSSA sensing pin) is also fine with a pull-down so my current state of knowledge is that I'll have to add the two pull-ups for TMS (R52)and TDI (R36) and MUST NOT ADD the pullup for TCK (R49) if I want to ensure stable JTAG operation, correct? Also, I imagine the SG_TST signal will interfere with TDO if I try to do stallguard stuff whilst JTAG debugging.


  • administrators

    We've never used JTAG debugging on the Duet WiFi, so you are on your own!

    A couple of suggestions;

    • If you find the use of TCK for VSSA sensing problematic, you can remove the 10K series resistor (and add the pullup);
    • If you have a revision 1.03 Duet then I think you will need to remove U13 to prevent it pulling TDO low.

    HTH David



  • @dc42 you as a seasoned firmware dev for TMC2660, can they only be used after they have been configured (to some degree) ? I (think) I have proper signals on ENN, STEP and DIR but the drivers are not moving at all.


  • administrators

    @ampex_fhm said in Using JTAG with the Duet Wifi:

    @dc42 you as a seasoned firmware dev for TMC2660, can they only be used after they have been configured (to some degree) ? I (think) I have proper signals on ENN, STEP and DIR but the drivers are not moving at all.

    I have never tried to use TMC2660 drivers without setting them up via SPI. How are you trying to set the motor current?



  • I had hoped the drivers would reset to some default state that was usable, but your reply confirmed that this is most likely not the case. Thanks for your reply!


 

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