Running RPI3 & Protoneer 2.6 but

Running RPI3 & Protoneer 2.6 with bCNC but… I have a few problems that I need help with.

This is a new build of my own version of several MPCNC designs.
It is based on a RaspberryPi3 running Protoneer’s V510 package on 16gb and/or 32gb sdcards. I have everything working mechanically and electronically (I think) and can run some sample GRBL routines that I wrote up and everything ALMOST works fine. I haven’t cut wood yet, but my 27"x24"x15" CNC with a DeWalt 1/4" router all move calibated distances.
Running a CNC is new to me as is GRBL but I’m getting the hang of it. I could use some input from the forum as to explain/correct the following issues:

  1. Issuing a G28 command some axis home in the opposite direction of when I issue a $H command.

  2. In bCNC when looking at $$ parameters they don’t match the parameters shown when checking parameters using the “CAM” tab.

  3. After running successfully and exercising all aspects of operation, if I close bCNC and shutdown the Pi, it won’t boot back up using the same SDcard. I have to use a newly generated boot SDcard. I’m doing something stupid, but I don’t what it is. Makes no difference if I run CNC.js or not.

  4. Is there a way in bCNC to zero out the MPos indicators once I get the machine homed? The WPos indicators read fine but I don’t know how to zero out MPos.

  5. Going from bCNC to UGS it shows the UGS always shows positions as zeroes even though when leaving bCNC the WPos and MPos positions are something other than zeroes and the machine is not zeroed. Do I need to home the machine where MPos is all zeroes before closing bCNC and opening UGS?
    is there a better way?

My CNC machine is on a wooden base using 4040 rails for X and Y with skate bearings. The Z axis runs on Delrin slides. All motors are NEMA 23 and all use external Stepper drivers (Y & Z are 8 wire steppers and X is temporarily a 4 wire stepper). Limit switches in parallel for each axis. Using a 30 volt power supply. Also hooked up RED leds for limit switches on each axis. That’s all I can think of, I’ll send photos when I get back to my PC.


Welcome to the forums!

With regard to the Pi, one idea that come to me first is the shutdown process. I have heard that you cannot shutdown the Pi just by removing power, it will shut down but there are consequences. The most common consequence it that the SD card is corrupted.

Do you have a programmatic shutdown in bCNC? That is, can you tell the Pi to do a shutdown from within the program. Octopi has a shutdown menu item. When you select it Octopi sends a PiOS shutdown command without you needing to exit the program and issue the command in a terminal.

If you have a monitor and keyboard connected to the pi, are you issuing a shutdown command in the terminal, or using a desktop icon to shutdown the Pi?

I can’t help you with the rest of your questions.


That only happens rarely, even with a hard shutdown. I agree, I thought of that too, but in my experience, it is much more rare than every time. Besides, it sounds like they are sitting it down with the shutdown menu.

Prontoneer that’s a name I’ve not heard in a long time…

My memory is that bcnc runs only on the desktop. The instructions told me to connect over remote desktop. UGS too. My guess is you are sitting it down via the correct shutdown menu.

What I think might be happening is that you aren’t completely cycling power to get it back up. Maybe something like the 12V is still powering the pi. It may also be doing something like expanding the file system (which it only does once) and it looks like it is broken, but it is just thinking. Attaching a monitor directly to the HDMI will give you a clue as to what step it is on.

  1. Grbl is different that Marlin. $H is one of the differences.

  2. I don’t use bCNC either, but my guess is that cam has speeds set for the material, and $$ is set for the machine (and should be higher). Not sure which settings you’re concerned with.

  3. Already talked about that.

  4. Mpos is machine coordinates, which get set to zero when you home. Wpos is work (and this is what actually matters). Grbl has a lot of coordinate frame features. I learned them by clicking buttons in cncjs.

  5. Are you sure UGS is connected? It may be that bcnc still has it open.

I shut down the bCNC program by:

  1. selecting EXIT
  2. Normal RPi shutdown
  3. Completely turn off power after PI stops blinking and HDMI screen has no signal. Power switch shuts off USB-C for power to RPi (thus the attached Protoneer) and the 30 VDC stepper power supply.

I have it running with an HDMI output to a screen and keyboard and mouse through a powered USB hub. Also, the Pi never acknowledges any USB plug with a XDCard adapter on the Pi. It all works on the PC. Plus I think the Pi3 won’t even come up if the USB/XDcard adapter is installed.

When the system won’t come up with a used XDcard, the Pi just flshes for a while then stops flashing without anything showing up on the screen. A newly formated XDcard and it all works fine. Power shutdown has been to close bCNC, then an orderly shut down of the Pi using the Shutdown menu and when the Pi stops flashing and the HDMI has no signal I shut off power to a strip with the USB-C charger (3amp) to the Pi and 115vac to the 30 VDC stepper power supply. I do get connected to UGS and can operate
the CNC but I MUST remember that machine positions are NOT at zero as indicated. I guess I’ll play around with CNC.js some more from my PC. I have to watch the CNC remotely by repositioning the the Octoprint camera on my 3D printer. Also trying to firugre out the GRBL macro operations.