Access to drive signals on Duet 2 WiFi



  • Hi,

    I currently have a printer using a Duet 2 WiFi with a Duex 5.

    I would like to obtain access to at least 3 of the 5 sets (2,3,4,5,6) of the drive signals E#_EN, E#_DIR, E#_STEP.

    Is it feasible to connect a E3D external drive breakout board to the "middle" of the flat cable connecting the Duet to the Duex?

    Could the signals from the Duet successfully drive both the inputs to the breakout board and the Duex?

    If not could I break the connections for just those signals from the breakout board to the Duex?

    Thanks.

    And yes it's a strange idea.

    Frederick



  • @fcwilt said in Access to drive signals on Duet 2 WiFi:

    E3D external drive breakout board

    I would think it worth trying. According to the picture below (is it the right one?) it uses SN75ALS192 which consumes at most 0.1ma. You can try connecting in parallel and see if you get too much signal distortion (with an oscilloscope or just observe if things behave strange).

    Alternatively you can design your own PCB that 'sits in the middle'.

    https://ooznest.co.uk/product/duet-expansion-breakout-board/



  • Thanks.

    You're right. Might as well try it.

    I have the parts and a scope - just need to find some quiet time.

    Frederick


  • administrators

    @fcwilt said in Access to drive signals on Duet 2 WiFi:

    Hi,

    I currently have a printer using a Duet 2 WiFi with a Duex 5.

    I would like to obtain access to at least 3 of the 5 sets (2,3,4,5,6) of the drive signals E#_EN, E#_DIR, E#_STEP.

    Is it feasible to connect a E3D external drive breakout board to the "middle" of the flat cable connecting the Duet to the Duex?

    Could the signals from the Duet successfully drive both the inputs to the breakout board and the Duex?

    If not could I break the connections for just those signals from the breakout board to the Duex?

    Thanks.

    And yes it's a strange idea.

    Frederick

    Yes, using a ribbon cable with three IDC connectors on it will work. However, the Enable signals on the breakout board won't work, because RRF will detect the DueX5 and use them as CS signals for the on-board drivers. Most external drivers don't need the Enable signals anyway, if you don't mind the drivers being permanently enabled.



  • @dc42

    Thanks for that valuable info.

    Assuming there was no Duex board what does the firmware do with those Enable signals?

    Frederick


  • administrators

    Without a DueX board, those Enable signals are available. With a DueX2 board, the three enable signals corresponding to the drivers not present on the DueX2 are available.



  • @dc42 said in Access to drive signals on Duet 2 WiFi:

    Without a DueX board, those Enable signals are available. With a DueX2 board, the three enable signals corresponding to the drivers not present on the DueX2 are available.

    Sorry - I meant what purpose do the signals serve aside from the obvious function?

    In a normal setup of just the Duet WiFi and the Duex 5 what conditions determine if the Enable signal is active or inactive?

    Thanks.

    Frederick


  • administrators

    In a Duet + DueX5 setup, those signals on the ribbon cable are chip select signals for the TMC2660 drivers on the DueX5.



  • @fcwilt said in Access to drive signals on Duet 2 WiFi:

    And yes it's a strange idea.

    Can you tell us what's the plan?



  • @zapta said in Access to drive signals on Duet 2 WiFi:

    Can you tell us what's the plan?

    I just wanted to experiment with some closes loop stepper systems - both cheap and not cheap - just to see if there is any noticeable difference in print quality.

    I've heard some folks say there is, some say there is not.

    I may find nothing definitive but I will most surely enjoy the experiment.

    Frederick



  • @fcwilt, sounds exciting. Please let us know if you will find anything interesting.


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