DueX5 External Drivers

  • I'm planning out upgrading my printers electronics to the Duet Wifi and ran into some I/O slot questions. My machine is a rather large one with 4 each of extruders, heaters, thermistors, fans, and relays for pneumatics. The XY gantry system is made up of a couple 6.3A NEMA 34's with 3.0A NEMA 23's running the Z, all from external drivers. As a result of using external motor drivers and needing quite a few extra I/O connections I'm looking at utilizing the DueX5 extension board.

    My Question: Can I "hack" the 50 pin ribbon cable running from the Duet Wifi to the DueX5 by diverting the Step/Dir/Enable pins for each of the 5 drivers while still maintaining the integrity of the extra connections of the DueX5?

    I found this thread that discusses a similar question, however I wanted to verify that this is possible for my specific case.

  • I think you'd want to use the expansion/breakout board, not the Duex5.

    Could run the 4 extruders from the Duet itself, and the 2 NEMA34s and however many NEMA23s from the breakout board.


  • administrators

    Unless your 3A Nema 23 motors are long, high-inductance types, you could drive them from the Duet Wifi (or DueX). So you need use external drivers only for your Nema 34 motors. But I understand that this is an upgrade, so you already have the drivers.

    Each drive position on the Duet must be either a TMC2660 driver or an external driver; except for the last two (drivers 10 and 11) which can only be external drivers connected to the CONN_LCD connector. Your best option may be to use a DueX2 board. This would provide you with the 4 extruder heaters/thermistors/fans you want, along with 7 TMC2660 drivers. You would be able to connect 3 external drivers to the DueX2, and a further 2 to the CONN_LCD socket.

    We made a few hybrid DueX2/DueX5 boards for an OEM who wanted all 5 extra heater and fan channels but needed to add 3 external drivers; however this isn't a stock item.

  • I work with OP and am familiar with his situation. Let me see if I can clarify his ask. We already have the machine built with drivers and electronics in place. We are replacing the current azteeeg board with a duet wifi and we want to try and keep everything in place. In a perfect world, with our current configuration, we would modify a ribbon cable to use the duex5 for all of the fans, heaters, and thermistors, but break off step, dir, and en wires to power our external drivers for X, Y, and Z (to clarify, these wires will never reach the duex5). We would use the drivers on the Duet WiFi to power the 4 Nema 17 extruders and remap our axes in config.g.

    The question: Will this break anything. We intend to use level shifters between the duet and our drivers.

  • administrators

    As I tried to explain in my previous post, if you have a TMC2660 driver on a particular channel, you cannot substitute an external driver for it. This is because the line that would be the Enable line for the external driver is used as the Chip Select line when a TMC2660 is present in that position. Therefore, using a DueX5 limits you to 2 external drivers; whereas using a DueX2 allows you to use 5.

    In principle it would be possible to cut the SPI wires that drive the TMC2660s on the DueX in the ribbon cable, but it would still require a firmware change so that the firmware known that drivers 5-9 are external.

    I'll ask my colleagues whether they have any plans to make some more of the DueX2/X5 hybrid boards.

  • Thanks for the clearing our misunderstanding up.

    It looks like the DueX2 method will work for us. However, I'd certainly be interested in the hybrid boards if another run was on the near horizon.


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