SOLVED External stepper drivers multiplying steps by 4



  • Hey all,

    I have a cloned duet board where driver P4 has failed. To address this, I've put in a TB67S249FTG from Pololu (https://www.pololu.com/product/3096) in stepstick form.

    DMODE0, 1 and 2 have all been jumpered (resulting in 1/32 microsteps) and connected to 3.3V, EN/STEP/DIR/GND are all connected appropriately. My E motor is 0.9 degree, and I nominally had Esteps at 846.38, but now, it is exactly 1/4 the value it was originally at 211.60 (211.595 rounded).

    I've simply enabled the motor with:
    M569 P5 S1
    M584 X0 Y1 Z2:3 E5 ; set drive mapping Z2=Left, Z4=Right 4 is dead, moved to 3
    M350 X32 Y32 Z16 E1 I1 ; I've also tried various microstep settings, but that's a driver feature, it seems and irrelevant here
    ;M92 X400.00 Y400.00 Z1600.00 E846.38 ; set steps per mm on original 2660
    M92 X400.00 Y400.00 Z1600.00 E211.6 ; set steps per mm

    Is there something I'm missing? Thanks!



  • Do you happen to have an oscilloscope, Can you issue manually a small movement and see how many step pulses you get?

    And a dumb question, why not replacing the faulty TMC2660?



  • @zapta said in External stepper drivers multiplying steps by 4:

    Do you happen to have an oscilloscope, Can you issue manually a small movement and see how many step pulses you get?
    And a dumb question, why not replacing the faulty TMC2660?

    Nope, I don't have an oscope 😞

    That's not a dumb question, I also don't have equipment to properly replace the driver myself (only have a soldering iron with a knife tip at best, no reflow heat gun). My next best solution is to just use an external driver like this.


  • administrators

    @pfn said in External stepper drivers multiplying steps by 4:

    That's not a dumb question, I also don't have equipment to properly replace the driver myself (only have a soldering iron with a knife tip at best, no reflow heat gun). My next best solution is to just use an external driver like this.

    Look up ChipQuik low-temperature solder, intended for desoldering chips. There are videos about using it on YouTube. There is no thermal pad under the TMC2660.



  • @dc42 said in External stepper drivers multiplying steps by 4:

    Look up ChipQuik low-temperature solder, intended for desoldering chips. There are videos about using it on YouTube. There is no thermal pad under the TMC2660.

    ChipQuik is so neat! I'm going to pick up some to try out.

    Before I get to that, though, do you have any idea why my steps are 1/4 of what they were before to extrude 1mm? What am I failing to understand?

    Thanks for the suggestion!



  • @pfn, alternatively you can go to a local cellphone or computer technician and ask them to replace the chip.



  • @zapta said in External stepper drivers multiplying steps by 4:

    @pfn, alternatively you can go to a local cellphone or computer technician and ask them to replace the chip.

    Considering prices here, probably cheaper to just DIY with chipquik. Thanks for the suggestion. Now back to trying to understand why my steps are 1/4 what they were previously.



  • I want to try one day chip removals like this with this tool.

    https://youtu.be/o3vK0fikX80?t=665

    Could be a func practice, removing all the components from my Duet2 and putting them back. 😉



  • @zapta @dc42 turns out my stepper driver is faulty and would not accept x32 microsteps (I had jumpered it DMODE0/1/2 high), it gave x4 instead. It basically ignored the DMODE0 level.

    That makes setting x8, 16 or 32 microsteps impossible.


  • administrators

    Thanks for the update, I'm glad you solved it.


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