Hello perhaps someone can help me clear up my confusion , I’m using a Nema 23 motor(57BYGH420 ) and an Arduino Uno with CNC shield 3v , I was using drivers A4988 and switched to DRV8825 now as I understand my motors are set with an amperage of 2A and which I cannot exceed or they will be blown , I understand that the VRef is x2 the value of the current so If I use a .75 voltage I would get 1.5 Amps across the motors which is good to keep the heat dissipation down on the drivers and also set the motors active but how do I set the current for a half step on the shield or does the driver act the same as the A4988 driver and automatically recognize the shield settings .

Thank you Kindly

Moving you to motors and such.

Could you take a few moments to READ THIS.
It will help you get the best out of the forum.


Motor current should be the same, regardless of micro steps.

so setting my current at .75 v should get my driver and motors working to start calibrating the machine .

so setting my current at .75 v should get my driver and motors working to start calibrating the machine .

What happens when you try it?

The Arduino system is great for learning-by-doing.

By the way, if you chose that motor because it can deliver the torque your project needs then it seems likely that it won't meet your requirement unless you have a driver that can provide the full current required by the motor. If this was my project I would like to have a driver that could provide 50% more current than the motor needs. It is usually not a good idea to use electronic components near to their stated limit.

Stepper Motor Basics
Simple Stepper Code

With my drivers installed and calibrated to .75v when i start UGS it does not show the setting but the Arduino Uno shows connection on com 3 , so my question is why does Arduino show connection but not the setting in UGS?

There could be a few reasons.

UGS will show a connection even if GRBL is not actually loaded to an Arduino.
That is the most common reason for not seeing any settings.

GRBL is just the middleman between steppers etc.
UGS is the front end for many of us although as you no doubt realise there are plenty of other alternatives.

Once you upload GRBL to your board which forms the firmware as such, then you can start to query settings.
Uploading anything else (sketch wise) to the board will overwrite GRBL.


Alright but by me not getting a reading UGS wont that mean that something is not right , does a software need to be added for the drv8825 to be seen my Arduino Uno or what am i ot understanding?

Yes you need to UPLOAD GRBL to your UNO or NANO before you can do much else.

Simply get a copy of the GRBL library and install it as you would any other library.
Once installed open the IDE and select the example GRBL UPLOAD and upload it.
You can ignore a memory warning if you get one.

Also not that if you are using any other type of board you may need a special port of GRBL itself to suite that architecture.


GRBL is already added to my Arduino Uno a long time ago 1.8.10 , now I'm wondering why I don't see anything when I start UGS after installing the new drivers before with the A4988 Even with no power to the board I would get the config now i don't get anything what I get is connected to come 3 then the baud rate but nothing more than that , could my Arduino Uno be blown or do I need to add a file to Arduino Uno to be able to see the drv8825 drivers

If the problem is that the motors are not working then, if it was my problem, I would start testing with a much simpler program than GRBL. Earlier I gave you a link to the code I would use.


You may also want to remove your connections / shields to the board and see if that helps you to see any GRBL settings.
That in its simplest form would tell you if the issue is your connections.
Most Arduino based CNC software can still see the board even if the extra hardware is not installed.

Also as Robin suggests there are also other ways of testing motors etc.


I think my Arduino Uno is blown when i try to upload to the basic blink and change the blink time it take a long time with an error at the end of trying to flash a new config for the blink time .

Well that would throw the cat among the pigeons for sure !