using tinyg with external stepper drivers.

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  • November 17, 2012 at 5:44 pm #3592
    freemoore
    Member

    Hi all,

    I want to get my Tinyg v7 board driving external stepper drivers.  I’m using fine wires through the vias on lines from pins 3 and 19 of each drv8811, and can see a 3.3v signal from the direction line (pin 3) but nothing from the step line (pin 19). The stepper driver needs 5v in the logic side, though, and I’m not sure how to go about converting the voltage.

    I’ve tried wiring it through an optocoupling parallel port breakout board, which should accept 3.3v signals and output 5v, but haven’t managed to get very far with that as the board needs an actual parallel port plugged in before it’ll enable outputs, and I’m not sure how to make it behave as if there is one.

    Alden, you mentioned hacking the limit switch pins to send step and direction signals – is this something you’ve done, or something I can change in the firmware?

    hope someone can help,

    Andy

    November 18, 2012 at 7:19 am #3593
    freemoore
    Member

    Amazing what a night’s sleep can do.  I had another crack at this this morning, using a sn54act245 ‘octal bus transceiver’ chip stolen from the parallel port breakout board. This is performing the level conversion and keeping up with the step rate, so I’ve now got the tinyg motion control working with external stepper drivers – my ideal situation!

    Next challenge is getting the spindle control to talk to a Huanyang VFD…

    all the best,

    Andy

    November 21, 2012 at 10:45 am #3598
    Riley
    Keymaster

    Well I am glad you got it working.  However, this is not really something we support.  Its your board however!  Knock yourself out.  But from our standpoint it introduces a bunch of issues with support etc!

    I am glad its working for you, and we are interested in seeing what you do with it.

     

    Riley

    November 21, 2012 at 1:07 pm #3602
    freemoore
    Member

    Aye, well, it would be a bit above and beyond the call of duty to support boards being messed with in this way, just a spot of moral support here and there is all I’d hope for.  As it is, I’ve blown the regulator U2 and am currently waiting for a replacement whilst hoping that it was only that that blew. Looking forward to more tinyg in use…

    best,

    A

    November 26, 2012 at 6:00 pm #3616
    Riley
    Keymaster

    You have our support!  Just to be clear.  Its just tough from our point of view to place the “stamp of approval” on it!  🙂  To let you know will be coming out with a modular board eventually that will allow for what you are doing.  However, there is not release date as of now.

     

    Sorry to hear about the vreg!  Keep us updated.

     

    Riley

    November 26, 2012 at 6:37 pm #3620
    freemoore
    Member

    Ah, lovely! Much appreciated.

    In case you can cast any light…I’ve replaced the regulator and checked the ftdi chip by desoldering & placing onto a sanguinololu board, from which it showed up in /dev just fine, then returning it to the tinyg.  The vreg is at about .28v-.33v at the 3.3v pins – any idea what might cause that?

    all the best

    Andy

    November 28, 2012 at 8:21 pm #3627
    Riley
    Keymaster

    Sorry,

     

    Without having it here I am not quite sure.

     

    Riley

    November 30, 2012 at 9:15 am #3635
    saci
    Member

    Hi all,
    Really TinyG is one of the most powerfull DIY cnc controller and I know that it’s very usefull as is in most case (3D printer, router, lathe or other…), but it’s possible that some people doesn’t longer have need power stage because there machines already have power drivers for motors or simply want to use more powerfull drivers or why not servomotors instead of the conventional stepper motors, in this case hacking the GPIO port to pinout the step/dir signals or implementing a new connector on the future PCB board release seems to be a good idea.

    November 30, 2012 at 9:27 am #3636
    saci
    Member

    Personally I have a machine with servomotors configured to be controlled directly by Step & Dir signals ( TTL 5v level and also 3.3v without problem!). I tried to make my own PCB with an ATXmega processor ( Slave ) programmed with the famous tinyG firmware ( thanks to Alden Hart and Synthetos Team for the great work!),and at the same time I had the idea to put a second ATmega processor ( Main ) with a personal firmware in order to add few interesting things like manual jogging buttons,tool length probing, LCD, SD card … and all this without changing the tinyG firmware that remains intact on the ATXmega.

    in this demo video an industrial grade brushless AC servomotor (a Parker 1.3KW motor W/ 8000cnt/rev encoder) with Allen Bradley servo drive (Ultra-100 series used in Follower Mode) is controlled by Step & Dir signals from the 4th axis pin out from the ATXmega port. When pressing “A axes” manual jogging buttons, the motor run smoothly responding to the acceleration and deceleration ramp defined only by tinyG settings . the jogging feed-rate is set by the potentiometer connected to an analog input pin on the main processor (ATmega).

    http://youtu.be/Nrsyejv-vwE

    this video shows that Tinyg is a really a sophisticated high quality controller which can be used not only in small machines but also in much larger applications…

    December 2, 2012 at 8:08 am #3642
    alden
    Member

    Saci,

    You are always out ahead with things. That is a really cool application and video. Thanks for posting.

    Alden

    March 28, 2013 at 7:08 pm #3962
    wenger
    Member

    TinyG main board with external stepper drivers is just the ticket for my needs too – any progress and/or ETA on that front?

    March 29, 2013 at 3:20 pm #3964
    alden
    Member

    Yes. We are prototyping a version 8 board that breaks out the stepper lines to external pins. We’re probably about 2 months away from first production.

    –Alden

    May 6, 2013 at 10:30 am #4113
    kkannan
    Member

    Looking forward to v8, this will make small CNCs with the sophistication of tinyg and the power of servos possible.

    -Kannan

    November 26, 2013 at 7:49 pm #4976
    RustRacer
    Member

    Freemore,
    I’m trying the same thing with TinyG v8 and an Oriental Motor/Vexta stepper driver. It’s one of their weird 5-phase things so I can’t drive it using the TinyG’s drivers. I just need the step and direction out of TinyG, but I can’t see any signal on the Step pin. I’ve tried different speeds and different settings on the scope. I even tried while actually running a 2-phase stepper connected directly to the TinyG’s driver, but still nothing from the Step output.

    How did you get something from the Step pin?

    November 27, 2013 at 8:11 pm #4985
    RustRacer
    Member

    Update: more tweaking of the scope finally showed me the 1us (yes, one microsecond) step pulse. I still couldn’t get either of 2 types of level-shifters from Adafruit to get the external stepper driver to respond. I’ve ordered the octal bus transceiver chip that Andy referred to above. If that doesn’t work I’ll probably give up and get a normal 2-phase stepper that the TinyG’s drivers can drive.

    Ben

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