WARNING: The author(s) assume absolutely no responsibility for any damage and/or disappointment that might occur as a result of following the instructions below. This project is currently still a work in progress and works only on Carvera Air. DO NOT TRY THIS AT HOME unless you understand what you're doing and are willing to deal with the issues and fix the bugs yourself (I might help with that, though).

Electrophorus is a project that allows you to convert a Carvera-family desktop CNC milling machine by Makera Inc. to use LinuxCNC as a controller with the help of a Raspberry Pi.

It works by offloading the real-time functions (pulsing the stepper drivers) to the Carvera board/firmware, while the computation-heavy parts (G-code parsing, trajectory planning, motion control, etc.) are handled by LinuxCNC running on the Raspberry Pi. If you're familiar with LinuxCNC concepts, the Carvera board acts as a Programmable Realtime Unit (PRU) on a BeagleBone or a limited version of a Mesa card.

I (@f355) don't have the big-brother Carvera (C1), so for now it is supposed to only work (or not :)) with Carvera Air (CA1).

The project started as a fork of the fantastic Remora project. The Remora authors say they "dont ...not support" LPC1768-based boards, so this is a hard-fork; the changes are not intended to be upstreamed, and the code has been rewritten almost completely.

• 3-axis linear motion with homing, limits, and stall alarms
• Spindle with feedback and stall alarm
• Probing, including TLO measurement on tool changes
• E-stop
• XHC WHB04B MPG pendant
• Temperature-based fan control for the case and the spindle fans
• Work light

• Machines other than Carvera Air (CA1)
• Rotary axis (no blockers, just needs to be configured)
• Main button, lid sensor, EXT port, beeper - the support is in place, they're just not used for anything
• LED strip (the implementation is somewhat involved, so it is deemed low-priority)
• X-axis flex compensation (not even started)

The communication between the machine's board and the Raspberry Pi is done over the SPI bus. Unfortunately, both SSP/SPI interfaces on the board are populated - SSP0 by the SD card and SSP1 by the ESP8266-based Wi-Fi module. We won't need either of those things, so we'll be plugging into the MicroSD port directly using a very cursed-looking cable. It is possible to use the Wi-Fi module pins too, but it is much harder since it requires physically modifying the board.

You'll need the following:

1. Carvera Air itself, obviously.
2. Raspberry Pi 5 (recommended) or 4B (not well-tested) with a suitable power supply and a MicroSD card.
3. MicroSD breakout board - a PCB with a MicroSD card shape on one end and solder points/terminals on the other. I used one end of a MicroSD extension cable; they're readily available on the internet. AliExpress has very cheap breakout boards with pin headers, available as "microsd sniffe" (sic, not "sniffer"). Alternatively, you can design the PCB yourself and cut it on the Carvera (please share your design if you do).
4. DuPont 2.54 mm / 0.1" pitch pin header connectors, female. A single 40-pin connector housing for the Raspberry Pi is recommended to avoid counting pins every time you plug in the cable. If you choose to connect the SWD port, you'll need a 5-pin connector as well.
5. Wires to tie it all together, of a suitable gauge, and a way to do that (soldering iron, crimping tool, heat-shrink, etc.)

• The Raspberry Pi pins are numbered according to the official pinout. The pin numbers refer to the physical connector pins, not the logical GPIO numbers.
• "Wire color" column is purely informational and refers to the colors on the photos below, feel free to use any colors you want.
• Keep the wires short to minimize interference - 10-15 cm is a good length.
• Double- and triple-check when done, improper wiring can damage the Carvera board.

It's the MicroSD port. Required; it is the main communication channel between the machine and LinuxCNC.

Pins are numbered according to the MicroSD pinout in SPI mode. Your breakout board might have extra grounds or even a completely different pinout on the cable side, make sure to carefully check which pin is which. On the photos below, the black ground wire is in the "wrong" place because my board had extra grounds, and it was more convenient to connect it there.

It's a 5-pin DuPont pin header below and to the right of the MCU, used for flashing, resetting, and debugging the firmware. You can omit it and flash the firmware using an SD card, but it is much more convenient to do it without unplugging the SPI cable.

Pins are numbered bottom-to-top, according to the silkscreen.

The resulting cable should look something like this (ignore the black-green JST-XH lead, it is not necessary):

All connected together:

Please excuse the crudity of the model; I didn't have time to build it to scale or to paint it. Coming up with a way to permanently mount the Raspberry Pi while providing adequate cooling is left as an exercise to the reader.

The external emergency stop button that comes with these machines is a normally-open button. That poses a pretty serious safety problem: if the button wiring fails, or you simply forget to plug it in by accident, the machine would still run just fine. Then, if an emergency happens and you press the button, nothing would happen.

Because of that, Electrophorus requires you to re-wire the button for the normally-closed operation.

It is very easy to do, and it is a good idea in general, even if you are using the stock firmware. You need to open the button housing by removing the four screws on the top, re-plug the red wire from the NO to the NC terminal, and assemble it back.

If you are using the stock/community firmware, you need to start the machine with the button disconnected, type config-set sd e_stop_pin 0.20!^ (for Carvera Air) or config-set sd e_stop_pin 0.26^ (for Carvera) in the MDI console, connect the button, and reset the machine. If you need to go back to NO for some reason (you shouldn't), the command is the same, but with "!" removed/added.

As of now, Electrophorus only supports "headless" mode, meaning that you connect to the Raspberry Pi's desktop through a web browser and control it from there. There's no support for running it with a monitor and a keyboard attached (pull requests welcome).

Start with the Raspberry Pi Imager as usual and write the Raspberry Pi OS Lite to the SD card. You need to use the Lite variant - full images use Wayland as the display server, which has pretty serious detrimental effects on the LinuxCNC performance. Make sure to enable SSH, configure the Wi-Fi network and apply any other customizations you need.

Boot the Raspberry Pi from the SD card and connect to it over SSH. Then, install git:

sudo apt update
sudo apt install git

Clone this repository:

git clone https://github.com/f355/electrophorus.git
cd electrophorus

...and run the installer script:

./install.sh

It would take a while, be patient. After finishing, the installer would ask you to reboot the Raspberry Pi. Do that by issuing sudo reboot.

After rebooting, connect to the Raspberry Pi again and check if the remote desktop is working by opening http://<pi_ip_or_hostname>/vnc.html in your browser and pressing the "Connect" button. You should see the desktop.

The installer also configures an SMB share for the linuxcnc folder, so you can access it from Windows or macOS machines on the same network and upload G-code files. Put them in the nc_files folder and they will be available in LinuxCNC.

If you have connected the SWD port, you can flash the firmware directly to the Carvera board. From an SSH session on the Raspberry Pi or a terminal on the remote desktop:

cd ~/electrophorus
./flash.sh

If the machine beeps and reboots, it has worked.

Alternatively, you can flash it through the SD card as usual, the firmware should be in ~/electrophorus/cmake-build-release/electrophorus.bin.

Start LinuxCNC by opening http://<pi_ip_or_hostname>/vnc.html in your browser, connecting to the remote desktop, and launching LinuxCNC from the "Applications" menu on the top left, "CNC" → "LinuxCNC". In the window that opens, scroll up if needed and select "My Configurations" → "carvera" → "carvera_air_3axis". Check the box to create a desktop shortcut if you want to, and press OK.

Make sure the SPI cable is connected and the machine is powered on, then press the red "ESTOP SET" button in the top right corner. The button should turn green. If it doesn't, check the connections and try again. Next, press the "MACHINE OFF" button; it should also turn green. Finally, press the "HOME ALL" button. The machine should home itself, and congratulations, you are ready to go!

Describing how to use LinuxCNC is beyond the scope of this project; please refer to the LinuxCNC documentation and forums for more information.

There's a LinuxCNC post-processor for Fusion 360 in the Autodesk's library, just search for "LinuxCNC (EMC2)". You can use the community profile for Fusion 360, with the machine simulation and all other bells and whistles, just change the post-processor to the one mentioned above.

MakeraCAM outputs pretty standard G-code, so it might work out of the box, but it has not been tested.

This project is licensed under the GNU General Public License v3.0 or later (GPL-3.0-or-later), except where a file header explicitly states a different license. Third-party components retain their original licenses; see individual file headers. See LICENSE.md.

Non-binding notice (for the avoidance of doubt, not a license term and imposing no additional restrictions under GPL-3.0-or-later): the author requests that Makera Inc. (maker of the Carvera/Makera family of CNC machines) and affiliated entities refrain from using this work, unless and until they demonstrably and on an ongoing basis adhere to the principles of open-source licensing in their own work; entities seeking alternative rights may contact the author to negotiate a separate dual-licensing agreement.

The full documentation is at https://remora-docs.readthedocs.io/en/latest/ Note: Docs have not been updated for 1.0.0_rc

Remora is a free, opensource LinuxCNC component and Programmable Realtime Unit (PRU) firmware to allow LPC176x and STM32F4 based controller boards to be used in conjuction with a Raspberry Pi to implement a LinuxCNC based CNC controller.

Having a low cost and accessable hardware platform for LinuxCNC is important if we want to use LinuxCNC for 3D printing for example. Having a controller box the size of the printer itself makes no sense in this applicatoin. A SoC based single board computer is ideal in this application. Although developed for 3D Printing, Remora (and LinuxCNC) is highly flexible and configurable for other CNC applications.

Remora has been in use amd development since 2017. Starting on Raspberry Pi 3B and 3B+ eventhough at the time it was percieved that the Raspberry Pi was not a viable hardware for LinuxCNC.

With the release of the RPi 4 the LinuxCNC community now supports the hardware, with LinuxCNC and Preempt-RT Kernel packages now available from the LinuxCNC repository. This now greatly simplifies the build of a Raspberry Pi based CNC controller.