Help for wiring up CNCv3 - DRV8825 -R32 - D1 #wemos #esp32 #250p #arduino #d1



my name is Stefan. I'm newbie in terms of telescopes and just bought a Skywatcher Dobson 10" 250p.
I came across this awesome site full of great ideas and switched my former Intention to build a cnc machine, to motorizing my Dobson.

I do have most of the parts shown at this wiki entry, which does supply a lot of information, but unfortunately not detailed enough for me.

 I'm not the best electrician (although I try to get better :)), so I do have some missing knowledge on wiring up the components.

I own this kit:
  • 3 Nema 17 1.8 200 steps
  • 4 DRV8825
  • Cncv3 shield
  • 3 Endstops
  • D1 R32
  • D1 mini
  • DS3132RTC
  • GT-U7 GPS
  • BME/BMP280
  • Active Buzzer 5v
  • 3d printer
  • soldering station
  • elect. accessories (capacitors, etc.)

Of course I know that with this kind of components there is not much to expect in terms of accuracy, but I would be glad to use it as guiding help for visual scoping
and to learn more about the night sky, telescopes and the ecosystem around it.

My scope with 3d printed gears and endstoppers: 

Gear reduction on azimuth 44:1 and altitude 22:1

I read the wiki up and down and found a lot, so that I was able to tune the stepper drivers to 0.75A.
Configuring OnStep and uploading it to the R32 worked and I was able to steer both steppers manually with the Android app.

Goto did not work for me, as the dobson just turned around in circles after setting it up aligning as described here.

So there a few questions, I do not find an answer for and would be very pleased if someone could shed some light into it.

  1. DRV8825 the 1.5A (0.75A) are without heatsink - I read somewhere that with heatsink 2A (1A) max is possible, true and does this improve something?
  2. Is OnStepX possible to run the SWS on the same R32 or do I always have to use the D1 mini additionally
  3. How would I connect the D1 mini to use the SWS for accessing OnStep?
  4. I did not get the endstoppers to work, when configuring the as LimitSense Low - I guess also the wiring was wrong...
  5. How do I wire up the additional components? It was not possible for me to get them to work, I think the reason is setting the correct pins.

Here are images of my components as well as my current config for OnStep:

Any help would be appreciated, thank you!

Best regards


George Cushing

Save yourself and everyone else some headaches, ditch the CNC3. Just want the PCB. I can get it to you for $10. My description here.


Hi George,
thanks for your offer. Shipping to Germany is no problem?

I want also to add a motor focuser at a later point, is that possible given that I see only 2 stepper driver slots on the design?

Fernando Nino Sr

Check out Oddvar Naess mod on his EQ5 mount, he has a wiring diagram for some of it using the same items you have. Also download the PDF file, much more information.

Chris Whitener

Try without limits switches set.  and without home.  Sometimes these take a bit of understanding.
The SWS is separate.  it needs to be connected to a serial port.


Hi Fernando,

thanks for the link, unfortunately he uses the same link I tried myself for wiring but did not succeed :(

George Cushing

Yes, I spent some time on this. The approach I would take is to use these pins except Aux8.

And IO32 & IO33 for STP and DIR. They are accessible here.


Fernando Nino Sr

Stefan, On the Wemos/CNC wiki page, way down the bottom, have to add the extra pins on the Wemos D1 to use Ic2 devices. So you would need the four pins, SCL, SDA, GRD and V5 or V3 depends on the module power requirement.