- Significant improvements in the planner. Removed or reordered
repetitive and expensive calculations by order of importance:
recalculating unchanged blocks, trig functions [sin(), cos(), tan()],
sqrt(), divides, and multiplications. Blocks long enough for nominal
speed to be guaranteed to be reached ignored by planner. Done by
introducing two uint8_t flags per block. Reduced computational overhead
by an order of magnitude. - Arc motion generation completely
re-written and optimized. Now runs with acceleration planner. Removed
all but one trig function (atan2) from initialization. Streamlined
computations. Segment target locations generated by vector
transformation and small angle approximation. Arc path correction
implemented for accumulated error of approximation and single precision
calculation of Arduino. Bug fix in message passing.
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h1. Grbl - An embedded g-code interpreter and motion-controller for the Arduino/AVR328 microcontroller
Grbl is a no-compromise, high performance, low cost alternative to parallel-port-based motion control for CNC milling. It will run on a vanilla Arduino (Duemillanove/Uno) as long as it sports an Atmega 328.
The controller is written in highly optimized C utilizing every clever feature of the AVR-chips to achieve precise timing and asynchronous operation. It is able to maintain more than 30kHz of stable, jitter free control pulses.
It accepts standards-compliant G-code and has been tested with the output of several CAM tools with no problems. Arcs, circles and helical motion are fully supported - but no support for tool offsets, functions or variables as these are apocryphal and fell into disuse after humans left G-code authoring to machines some time in the 80s.
Grbl includes full acceleration management with look ahead. That means the controller will look up to 20 motions into the future and plan its velocities ahead to deliver smooth acceleration and jerk-free cornering.
*Important note for Atmega 168 users:* Grbl used to be compatible with both the older Ardunios running atmega 168 and the newer with 328p. The full version of Grbl now compiles without support for circles/arcs if you target 168. If you need arcs, but not acceleration-management I am still maintaining Grbl 0.51 "in the branch called 'v0_51'":https://github.com/simen/grbl/tree/v0_51.
*Note for users upgrading from 0.51 to 0.6:* The new version has new and improved default pin-out. If nothing works when you upgrade, that is because the pulse trains are coming from the wrong pins. This is a simple matter of editing config.h – the whole legacy pin assignment is there for you to uncomment.
_The project was initially inspired by the Arduino GCode Interpreter by Mike Ellery_
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