Custom board suggestions

I might have an opportunity to have a ESP32 based board made to suit our needs.

That means as is GRBL-esp32 or marlin, has micro SD, USB, headless wifi/bluetooth built in. The only downside is very limited IO.

So what is ideal to have. Thinking MP3DP repeat and the CNC’s, this should cover most all builds outside the V1 World as well.


-full UART on all 6 drivers (2209), (XXYYZ, XYYZZ, ZZZXYE)
-6 endstops (5 endstops, one could be BL Touch or Z probe),
-2 Thermistors, (hot end and bed) For a CNC these are open pins for?
-2 Mosfet (hot end and bed), For CNC these are open 12-24v controls
-2 Fans. Again CNC open ports (laser), printing this is print fan and e fan.

Since it is headless we can skip the LCD headers and save a ton of pins.

What else?

Reverse current protection on the power, drivers, and endstop ports (all IO if possible).

Endstop pins next to stepper pins for ease of wiring. Maybe endstop LED indicators like the SKR Pro.


Would it have the ESP32 soldered on or would it have a header to drop an expressif module on?

I think soldered but maybe drop in is an option (probably a few dollars extra).

  1. Have you tried Marlin on the ESP32? It seems a bit niche. I would be curious to see if it has enough users so we aren’t the only ones working on bugs. If you didn’t want to support the repeat, then I would have no worries with firmware (grblesp or fluidNC).

  2. That still seems like too much IO without a daughter chip. The 6port Board Bart made has a dedicated second chip that handles a ton of IO and only talks to the esp over a few pins. The Bart Dring MPCNC board has more than I thought was possible, it has 5 drivers (connected in a funky way), 3 endstops, no fans or heaters, no driver uart. If I was at my desktop I would link the schematic to give you an idea. Several of the IO on an ESP32 is input only (6 pins, like 34-40?).

  3. On the pins with MOSFETs, I think you could easily pull the pin before the MOSFET. So you would get a “normal” 3.3V PWM and also the ground sink MOSFET output for fans. That would be ideal for a laser.

  4. Do you want a custom board? I am a firm believer that more users means fewer problems (because bugs get found sooner. That only leads to better products if the people who can fix the problems are beholden to those users). Having a board that is already or is soon to be popular would mean that we would not be alone in finding and fixing bugs. Improvements would come for free from those other communities and they would benefit from our improvements.

This for sure. The way I figured, I count 31 GPIO on a WROOM32, 3 pins each driver (18) (step,dir,uart), (1) global driver enable, (6) endstops, (2) therms, (2) fets, (2) fans. And there’s nothing left for your serial programming/hardwired interface. EDIT: And 6 of those are used for the connection to the flash chip.

1- No but it is a possibility, I am not sure I would pursue this part I just hope it would make the board more broadly appealing. (longer usable life, bigger audience).

2-There is a daughter chip, it adds 24 more out only IO(?)? I will try to find the specs again.

3-cool! That should save a couple pins.

4- I am hoping to make a broadly appealing board, I am not interested in having a private board, just a board that does what we need and what most need for a reasonable price. The advantage is we would get to lay it out and have a input in the higher level development. The builder would hopefully still take care of outside sales other than what we have here.

If it did work out like I think the price with drivers would be about the same price as the mini rambo used to be, but would include the headless part so savings in the screen department. (I got a new test batch of LCD’s and they are not good).

I’m using a couple of these I2c expanders with an esp32 on another project
SparkFun 16 Output I/O Expander Breakout - SX1509 - BOB-13601 - SparkFun Electronics

you can daisy chain up to 4 together fairly easily

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Why not use Bart’s 6-pack board?

Ahh, I see Bart is trying to get someone else to make them.

Is that why he doesn’t have any? He provides all the files to get them made, I could look into it. I asked about it a while ago and didn’t really get an answer if I remember right.

Yea, he said he’s trying to get Seeed Studio to sell them.

W.r.t. Marlin. You would want to run that on your repeat printers. It may be fine. There is a HAL for esp32. But Marlin and the flavor of grbl you’re using both need to support that daughter chip. I am sure that will add some constraints. You wouldn’t want to find out that the daughter board IO was adding some delay and that was causing worse Z bed probing or something.

What I didn’t say the first time is that it sounds like a lot of fun. It would be very interesting to explore it, with no deadlines, and no rush. No matter what, it is going to be riskier than the Rambo. There will be things we have to learn. If I know anything about PCB design, it is that bugs will always exist there too. There are people who are very experienced and they find all kinds of stuff I wouldn’t. Hopefully the company you’re working with can see those things coming.

It also seems like a step in the right direction for being more modern. A built-in wifi interface is nice. The ESP32 is very fast.

Also, maybe it can be red and black. How awesome would that be?


Yes pretty exciting, no pressure type thing. It would be building off a current board or at least the experiences from that. Find out in a few days if I should get one of the old ones or maybe wait for a new one, not sure if that is a possibility. There is a custom touchscreen as well, but I have not looked at the github, other than a few pictures.

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Red solder mask and black silkscreen? Oooooooh.

An ESP based board does have some appeal. I quite like the ESP32 as a platform, and it seems versatile enough to be around for a while. I really like the idea of wifi, though the currently available interface is somewhat underwhelming. It has the basic functionality, I suppose, but not much beyond that.

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And most importantly, no supply issues with those chips currently.


That won’t happen until you get the board all finalized. :rofl:

Looks like uart is the hold up. 5-6 drivers are cool but 3 would need to have the same current and step rate. Not sure what that means for diagnostics either.


This sounds like a great idea and something I would definitely be interested in. I will probably be replacing my RAMPS setup when I build my Primo and so far I haven’t found anything that is readily available and reasonably priced that would do what I want (auto squaring, laser control, and ideally it would run GRBL or something more specific to subtractive manufacturing than Marlin)

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Needz RGB headers…

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I don’t think this one is going to pan out, but now I am looking into it further and learning new stuff.

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I’ve been waiting to pull the trigger on a board from Makerbase. They make a ESP32 driven 3d printer board called the Tiny Bee. Has all your wants except uart driver support and only 5 driver slots. But, theoretically will run Marlin or Grbl.