Stepper motor wont change direction Duex 2



  • I recently added on a Duex 2 to my Duet 2 to help drive more heaters and external stepper drivers. I'm using the test pins on the Duex 2 to send step and direction signals to the external stepper drivers on drive 7 and 8. The stepper motors turn just fine, but I can't get them to turn the other direction. don't currently have access to the duet as I write this, but here are the important lines in the config.g file.

    M569 P7 S1 T2:2:2:0
    M569 P8 S1 T2:2:2:0
    M584 E7:8
    

    I also went through with a multimeter and measured the direction pin while telling the motor to go in forward and in reverse. The direction pin is always pulled to logic high no matter what I do.

    I'm currently using firmware 3.1.1



  • @Cynopolis you should set the fourth parameter to 5 which is direction hold:

    Taa:bb:cc:dd (firmware 1.21 and later) Minimum driver step pulse width, step pulse interval, direction setup time and direction hold time, in microsecond
    from https://duet3d.dozuki.com/Wiki/Gcode#Section_M569_Set_motor_driver_direction_enable_polarity_and_step_pulse_timing

    A value of 5 is often correct. The other values should be higher also, maybe T5:5:5:5 as a start try. Most external driver have 2.5 as minimum for the first two parameters. The values can be looked up in the driver datasheets.



  • @JoergS5 , I tried setting all the parameters to T5:5:5:5 and that didn't change anything. I think the underlying issue is that when I measured the direction pin with a multimeter it was never pulled low at any point.



  • @Cynopolis which external drivers do you use, is a datasheet available?


  • administrators

    I can't see any reason why those direction pins would not be driven. The E4_DIR test pad should be connected directly to pin 16 of the expansion connector, and E5_DIR should be connected to pin 21. The DIR pins are the centre ones in each group of three test pads.



  • @JoergS5 The drivers I'm using were purchased by a former employee at the company I'm working for and there is no documentation on them. However, we have been using these drivers with success for at least a year without any issues in combination with the duet 2. Currently, I'm working around the direction limitation by wiring the direction pin to a switch and manually changing the direction when I need to.

    @dc42 Any suggestions for troubleshooting that I could try?



  • @Cynopolis I asked because external drivers may be used with 3.3 volt, but sometimes only with 5 volt. And I wanted to look up the timing diagrams. If you find any type information, this would be helpful.

    But to clarify, you told that you already used it with Duet2. Was it with the Expansion board and if yes, with the default 3.6 v or the special 5v wiring?



  • @JoergS5 I know the drivers I'm currently using respond to both 3.3v and 5v



  • @Cynopolis you said your signal is always high, maybe you need a pull-down resistor to take the signal down when signal is 0. (PS hope you connected Dir- with ground)