@johnsiddle, Hi John, You can get a datasheet for the Allegro A4988 here: https://www.allegromicro.com/~/media/Files/Datasheets/A4988-Datasheet.ashx?la=en&hash=B0052E915715F54E7338E1274BC43698E610D8A9 * MS1 - MS3 pin functions are described under: `Microstep Select (MSx).` on page 7 of the datasheet. Note that the pull down resistances referred to are internal to the device. * The table of Electrical Characteristics on page 4: `Logic Supply Current IDD` shows that if your Fpwm < 50kHz and the Arduino 5V rail can supply an extra 8mA then you can run the VDD pin from the Arduino 5V supply. * Pay close attention to the information under: `Application Layout` on page 12 of the datasheet.

Hi Andy, Thanks for replying. I take issue with you that the 100k resistors are internal as they are clearly shown in position in the PCB layout, located under the A4899 chips R4,R5 and R6. Since they appear to be redundant I wondered if there was a mistake and that possibly the link from pin2 to the +5v was incorrect and that the required Mode is Full Step 2 Phase.. All I need to know is, that the Mode as set up in the schematic is correct and that the designer wants the chips to run at 1/16th step 4w 2phase as the A4899 datasheet indicates. I had already downloaded the datasheet for the A4899 chips. Regards John

Hi John, Sorry but you have provided no link to any schematic or PCB that you are referring to. `uController (v1.5) Dated 2017-09-10` or parts of it returns no results from a search withing EasyEDA. Your opening statement `In the schematic and the pcb, each of the A4988 chips...` gives no reference to what they are, who might make them and where the schematic and the pcb are so you leave it to other people to figure out what you are talking about. If these schematic and PCB files are in EasyEDA then no-one but you can see it because you have no public projects. If these schematic and PCB files are outside of EasyEDA then you cannot expect people to comment on them if you do not provide a link to them. If you ask for help from other people please have the consideration to provide as much relevant and background information as you have available. Please do not assume that 'it's obvious' or that everyone else 'just knows' or has the time to go foraging on your behalf.

Hi Andy Sorry if I upset you since it appears to be a public EASYEDA project I thought you would understand the project I was referring to and the references I gave are the only ones that are on the schematic. The link is below. https://easyeda.com/dherrend/uController-11dbaeb7e3f046408e67acb03aba75f2 Regards John

I suspect that most of the people who register on EasyEDA are electronics engineers at some level, whether they be newbies, hobbyists, students, hackers or professionals. I doubt that there are many who are clairvoyants... You are posting under the username of `johnsiddle` which links to a user area with no public projects in it: https://easyeda.com/johnsiddle You sign your posts as `John`. I'm really struggling with how people are supposed to find a project apparently belonging to a user called `dherrendoerfer`: https://easyeda.com/dherrendoerfer which itself gets truncated in the link to the actual project: https://easyeda.com/dherrend/uController-11dbaeb7e3f046408e67acb03aba75f2 You see why that just might be the tiniest bit confusing? :)

`uController (v1.5) Dated 2017-09-10` just returns a page not found error but I must have mistyped `uController` when I searched for it earlier. A project called `uController` now appears in the search results but even so it is not clear if this is the right one since it appears under a different username.

As far as I can see the 10k pulldown resistors are completely redundant. `This gives a Mode sequence of one 16th Step at 4wire 2phase, is this what is intended or should some other Mode be intended and the Schematic is in-correct?` Why not contact Dirk Herrendoerfer via his You Tube channel?

Sorry: I meant `...100k pulldown resistors...`

Sorry Andy, I got the impression that Dirk and EASYEDA were one and the same, I will do as you suggest anttry to contact him direct. regards John

Hi John, Dirk seems to be one of our users who has done some good projects on EasyEDA and had gone on to publicize them on You Tube. And in a similar vein, I was baffled because I thought the project you were asking about was your own. It has prompted me to try to get a post about `How to ask for help` stuck at the top of all the forum pages to avoid this sort of confusion. This should appear in a few weeks after the next big version update. If you don't get a reply from Dirk, post back and I'll try to get my head round the circuit... though it's not something I've dealt with before and the application support from Allegro seems to be almost non-existent.