Raspberry Pi CNC v2.51
Contents
Overview
The RPI CNC Board combines a real-time CNC controller(Micro-controller running GRBL) with a powerful credit card size computer(Raspberry Pi).
By combining the two systems we have created an eco-system where the Raspberry Pi provides benefits like: Processing power, connectivity(IOT) and a well supported community.
The board plugs directly into the Raspberry Pi General Purpose Input/Output pins, with the micro-controller and Raspberry Pi communicating via serial. (/dev/ttyAMA0)
Availability and Update Notifications
Installation and configuration
IMPORTANT: None of the components should be powered while installing or configuring.
Wiring Diagram
... Diagram Will Be Updated To The 4 Stepper Setup Soon ...
Installation
- Start by fastening the spacers onto the Raspberry Pi.
- If the Stepper Driver micro-stepping jumper configuration is known it might be easier to install the jumpers before installing the Raspberry Pi CNC board.(Jumpers can also be fitted at a later stage)
- Plug the Micro-controller(Arduino Nano) and stepper drivers into the Raspberry Pi CNC board. We recommend turning the stepper driver current POD's to its minimum position.
- Plug the Raspberry Pi CNC board into the Raspberry Pi header and screw the board in place.
WARNING: Do not power up the board with stepper drivers installed if they are not connected to stepper motors. These stepper drivers are current limiting and will overheat if they are not connected.
Micro Stepping Jumpers
In the tables below High indicates that a Jumper is inserted and Low indicates that no jumper is inserted.
| Jumper 1 | Jumper 2 | Jumper 3 | Microstep Resolution |
| Low | Low | Low | Full step |
| High | Low | Low | 1/2 step |
| Low | High | Low | 1/4 step |
| High | High | Low | 1/8 step |
| High | High | High | 1/16 step |
| Jumper 1 | Jumper 2 | Jumper 3 | Microstep Resolution |
| Low | Low | Low | Full step |
| High | Low | Low | 1/2 step |
| Low | High | Low | 1/4 step |
| High | High | Low | 1/8 step |
| Low | Low | High | 1/16 step |
| High | Low | High | 1/32 step |
| Low | High | High | 1/32 step |
| High | High | High | 1/32 step |
End Stops
End Stops use normally-open push-button type switches. The End-stop socket shares a common ground that connects to each axis end-stop. The pins are pulled high by the micro controller's internal pull-ups and will activate the end-stop when the pin is connected to ground.
GRBL v0.9 setting $21 needs to be set to 1 to activate hard-limits. Setting $22 also activated the Homing functionality.
Clone Drive
The 4th Stepper Driver Socket can be configured to clone any of the other Axes. Configuration is done with the two rows of jumper headers situated under the Nano board.
... Updated Diagrams to follow soon ...
Removing all the jumpers for the two rows of headers disables the 4th Stepper Driver Socket.
External Drivers and Buttons
. . .
Software
In order for the GRBL to communicate with the Raspberry Pi, the hardware serial port on the Raspberry Pi needs to be enabled and working. HobbyTronics has a good tutorial on how to set it up and test it. Raspberry Pi Serial Port setup
Firmware (GRBL + Micro-Controller)
GRBL is the magic that does the actual control of the CNC machines.
For more details : GRBL
The Raspberry CNC board comes pre-loaded with GRBL but can be updated as follows : Flashing Grbl to an Arduino
User Interfaces (Raspberry Pi)
bCNC [Python][Recommended]
bCNC is a GRBL CNC command sender, auto-leveller and g-code editor.
We have created a special Raspberry Pi Image with bCNC pre-installed. Raspberry Pi CNC User Interface SD Card Image
Features:
- G-code sender + Editor - Compatible with GRBL 0.9i
- Workspace configuration (dialog for G54..G59 commands)
- Auto leveling, Z-probing and auto leveling by altering the g-code during sending
- Basic CAM features (profiling, drilling)
- User configurable database of materials, endmills, stock
- Graphically moving and arranging objects
- Web pendant to be used via smart phones
- Graphical display of the g-code, and workspace
- Extra's : Finger joint box generator
Source code is available at [1]
Install instructions - [2]
Serial Interface
The micro-controller is connected to the Rapsberry Pi via the GPIO serial pins. To connect to the onboard serial port of the Raspberry Pi you will need a serial terminal application like minicom or putty to connect.
- Serial port details (GRBL 0.9)
- Port : /dev/ttyAMA0
- Baud Rate : 115200
G-Code streaming script for GRBL [Python]
This is a simple Python script that allows you to send G-Code files to GRBL.
Download : Stream.py
Raspberry Pi CNC - Web interface
Hardware
Version 2.51
- Extra Stepper Drivers Socket that can clone one of the other Axes.
- End-stop + Probe line noise filters. Allows end stops to work with normal un-shielded cable.
- Breakout pins allowing external Stepper drivers to be hooked up.
Version 2.11
- Initial Version
- 3-Axis (XYZ)
- End Stop for each Axis (XYZ)
- Variable Speed Spindle / Laser Intensity control (PWM Spindle pin and Direction pin)
- Coolant control pin. (Extra output pin)
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