Reflashing Firmware

Hi everybody,

i hope somebody can help with the following problem. I can`t flash the firmware on my SO4

(need to change:

#define INVERT_SPINDLE_ENABLE_PIN // Default disabled. Uncomment to enable.
#define USE_SPINDLE_DIR_AS_ENABLE_PIN // Default disabled. Uncomment to enable.
for M3/M5 commands)

Followed the guides I found but when I want to compile in the Arduino IDE it says that it can`t be compiled for the board. I chose Arduino UNO in the IDE…

Help very appreciated…

Hi @Stefan,

First of all I have to ask: do you need to rebuild GRBL ? Just curious what you are trying to do with those two lines.

Officially I should state that if you don’t run the stock firmware, support may not be able to assist you.

Now if you have good reasons to rebuild GRBL, those instructions should get you there:

Note that the stock Shapeoko firmware has a few customizations, custom config.h linked here

At which step does it fail and what does it say ?
I have done this a few times successfully.

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I have a SuperPID2 installed with a changeover switch as well as an on/off switch. The problem is that the router keeps spinning at 5k when i send an M5 command through CNCjs or GSender.

I followed the Compiling Grbl guide (as per your link). The problem I am facing is that the Arduino IDE says on Step 5 from that guide (compiling) that it can`t compile for the board (Arduino UNO was selected as board).

What’s the specific message you are getting ? (screenshot maybe ?)

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Board selection:

after click “compile”:

Can you upload the config.h file that’s located under C:\Users\Stefa\Documents\Arduino\libraries\grbl on your PC ?

If should have a


which in turn should lead to the declaration of the miscellaneous variables that the compiler complains are missing

#define DEFAULTS_GENERIC did the trick.

It had #define DEFAULTS_SHAPEOKO_3 in it (that was from a thread in the shapeoko forum)

i was able to upload the firmware but the spindle keeps running at 5k RPM when i send an M5 command.

This then sounds like control input setup/issue on the VFD. There are various threads here, depending on what make/model you have

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I don’t own a superPID but this thread seems to indicate that the 5000 RPM lower limit is enforced by the superPID itself, UNLESS one toggles it in “manual” mode, which I understood was the purpose of wiring the spindle dir signal to the superPID “Run” input. Do you have the D13 signal wired between the shapeoko controller and superPID, and does it change state when you do M3/M5 ?

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Hi Julien,
I gave up on the SuperPID… it is a pain to have that working reliable. I decided to go for a 1.5KW spindle, might be easier and more effective (and not so noisy). Right now, I am reading through the forum to find a good solution as there are many China models on Amazon Germany. Any recommendations on it from your side?

Not really, shopping Ali or Amazon for chinese models is a a bit like playing Russian roulette (except you don’t die if you loose, worst case scenario you end up with a lemon).
A number of forum members (myself included) got G-penny water-cooled spindles and did not complain (I was quite happy with mine, came already grounded, runout was as low as advertised, and I used it for two years without issues).

If you have the Z-plus axis and you are “just” trying to swap your trim router with something less noisy and more practical to use, I would recommend looking at 800w water-cooled spindle models, they are similar in weight to trim routers, so more compatible with a lead-screw axis, less weight on the vwheels, etc. Unless you know for a fact that you need more power, they’re a good choice for Shapeokos.

I have the G-Penny water-cooled 800W spindle and accompanying VFD. Earthing was properly connected and bearings as true as I could tell by hand, I replaced the pond-pump water pump for an evaporative cooler machine and it has run for 8+ months flawlessly. This with the HDZ has been the single best upgrade to my 3XL. Pendant Jogger 2nd best, rotary axis 3rd best.

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I mean if the spindle is made poorly enough you could die. It is just really, really unlikely. If it comes apart at a high enough speed and you are nearby…

Seriously though this is a topic I will have to do more research on. As I use my machine more and more I think that a spindle with more control and potentially quieter could be very useful.

I love my 800W G-penny spindle. I got it because the bearings in my router were failing and don’t regret anything. I did have to replace the grease in the spindle bearings.


Once you have had a taste of quietness, low runout, auto RPM control, low RPM capability (edge finders) it’s hard to come back.

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I will probably run my current router until it starts to have issues and then that will be the replacement.

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